SB 3Z5' Issued January 13, 1913. U. S. DEPARTMENT OF AGRICULTURE. BUREAU OF PLANT INDUSTRY— BULLETIN NO. 263. B. T. GALLOWAY, Chief of Bureau. METHODS USED IN BREEDING ASPARAGUS FOR RUST RESISTANCE. J. B. NORTON, Physiologist, Cotton and Truck Disease and Su(i(ir-J'lan t Investigations. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1913. ^onogmp^ i Issued January 13, 1913. U. S. DEPARTMENT OF AGRICULTURE. BUREAU OF PLANT INDUSTRY— BULLETIN NO. 263. i| / B. T. GALLOWAY, Chief of Bureau. METHODS USED IN BREEDING ASPARAGUS FOR RUST RESISTANCE. J. B. NORTON, Physiologist, Cotton and Truck Disease and Sugar-Plant Investigations. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1913. f , BUREAU OF PLANT INDUSTRY Chief of Bureau, Beverly T. G.u,lowat. Assistant Chief of BuTeaUjVfnAAAU A.Taylor. Editor, J. E. Rockwell. Chief Clerk, James E. Jones. Cotton and Truck Disease and Sugar-Plant Investigations. SCIENTIFIC staff. W. A. Orton, Pathologist in Charge. H. A. Edson, J. B. Norton, and F.J. Pritehard, Physiologists. C. O. Tpwnsend and L. L. narter, Pathologists. W. W. Gilbert and H. B. Shaw, Assistant Pathologists. C. F. Clark, G. F. Miles, Venus W. Pool, Clara O. Jamieson, Ethel C. Field, and M. B. McKay, Scientific Assistants. W. B. Clark, Assistant Chemist. H. W. Wollenweber, Expert. E. C. Rittue, Assistant. A. C. Lewis, L. O. Watson, and Joseph Rosenbaum, Agents. 263 D. OF D. JA^! 21 1913 ADDITIONAL COPIES of this publication -TjL may be procured from the Superintend- ent of Documents, Government Printing OflBce, Washington, D. C, at 20 cents per copy LETTER OF TRANSMITTAL U. S. Department of Agriculture, Bureau of Plant Industry, Office of the Chief, Washington, D. C, July 29, 1912. Sir: I have the honor to transmit herewith a manuscript entitled "Methods Used in Breeding Asparagus for Rust Resistance," by Mr. J. B. Norton, Physiologist in the Office of Cotton and Truck Disease and Sugar-Plant Investigations, and to recommend its publication as Bulletin No. 263 of the Bureau series. This paper deals with the methods developed in the selection, pollination, and breeding of asparagus at Concord, Mass. The work was done in connection with the rust-resistant asparagus breed- ing investigations being conducted at Concord by this Bureau in cooperation with the Massachusetts Agricultural Experiment Station. The author desires to acknowledge the assistance of Mr. C. W. Prescott, of Concord, Mass., who, since the beginning of the work, has done everything possible to aid the breeding work, Mr. Frank Wheeler, of Concord, Mass., together with many other asparagus growers from various sections, has given active assistance in the work. Respectfully, B. T. Galloway, Chief of Bureau. Hon. James Wilson, Secretary of Agriculture. 263 '-* Q CONTENTS Page. Introduction "g History of asparagus rust 9 Occurrence of rust in America 9 Failm-e of spraying methods in the East 9 Previous attempts at breeding 10 Massachusetts Asparagus Growers' Association 11 Preliminary work 12 Nature of the disease 12 Effect of the disease 13 Collection of varieties 14 Varietal uniformity 16 Value of uniformity '. 18 Introduction of uncultivated species I9 Selection 20 Preliminary methods 20 Greenhouse infection 21 Judging rust resistance 21 Record of select plants 22 Protection of select plants from frost 22 Rust infection to secure select resistant plants 23 Causes of resistance 23 >Ecidial stage on resistant plants 23 Relation of structure to resistance 24 Relation of vigor to resistance 25 Breeding 27 Sex. 27 Pollination 28 Methods of hand pollination 29 Care of seed 31 Method of testing progeny ' 31 Use of biometry 32 Correlation studies 32 Duplicate tests 34 Use of correlation studies in breeding work 35 Vigor of seedlings of male A7-83 43 Rust resistance 45 Permanency of rust resistance 50 Seedlings of 1911 52 Bud propagation 53 Pedigree 53 Number 54 Name g^ Records 54 263 g 6 CONTENTS. Page. Plans for distribution 55 Suggestions to breeders and growers 55 Rust resistance 55 Isolation 56 Progeny bed 56 Value of breeding methods 57 Protection from beetles 58 Protection of nonimmune fields 58 Suggestions for rust prevention 59 Summary 60 263 ILLUSTRATIONS. PLATES. Pago. Plate I. Effect of rust on asparagus. Fig. 1. — An asparagus field on Cape Cod, Mass., killed out by severe attacks of rust and never replanted. . Fig. 2. — Field showing the effect of rust on a nonresistant variety of asparagus 10 II. An old asparagus field at Concord, Mass., killed out by rust 10 III. Different stages of Puccinia asparagi. Fig. 1. — Teleutospores of asparagus rust. Fig. 2. — Cluster-cup stage of rust on an asparagus stem 12 IV. Asparagus branch with sori of Puccinia asparagi in uredo and teleuto stages 12 V. Three plants of the same variety, B114, Argenteuil, showing wide dif- ferences in type of mature growth 16 VI. Types of asparagus shoots 16 VII. Flowers of Asparagus ofiicinalis. Fig. 1. — Male flowers, the lower with some of its perianth lobes removed to show the stamens and rudi- mentary ovary. Fig. 2. — Female flowers, the upper with some of its perianth lobes removed to show the ovary and rudimentary stamens 28 VIII. Female asparagus plant with branches covered by "glassine" bags to keep insects from pollinating the flowers with pollen fi'om unknown males, this plant being used to test the comparative resistance transmission of several males 28 IX. Fig. 1. — Asparagus fruit and seed. Fig. 2. — Asparagus stem, show- ing the effect of bagging flowers without pollination 28 X. Asparagus seedlings, showing comparative rust resistance. Fig. 1. — Seedlings of 1909 in September, 1909, after a severe attack of rust. Fig. 2. —Pedigree seedlings of 1910 in September, 1910, B 136-4 X A7-83, showing rust resistance. Fig. 3. — Pedigree seedlings of 1910 in September, 1910, B136-4, open fertilized, showing lack of resist- ance and vigor 28 XI. Plant "Washington," A7-83, showing the general type of the best breeding male used in the rust-resistant breeding work 46 XII. Plant "Martha," B32-39, showing the general type of the best breed- ing female used in the rust-resistant breeding work 46 XIII. Pedigree seedlings of 1911 after a severe attack of rust. Fig. 1. — Wakeman seedling stock, showing tops entirely killed by rust. Fig. 2.— "Martha Washington" stock (progeny B32-39 X A7-83), commercially immune plants with strong vigor 52 XIV. Pedigree seedlings of 1911 after a severe attack of rust, showing vari- able resistance of Standard Giant Argenteuil, all plants suffering from rust 52 XV. Pedigree seedlings of 1911 after a severe attack of rust, showing plants from Standard Reading Giant seed, some nearly immune, others rusty 52 263 7 8 ILLUSTRATIONS. Page. Plate XVI. Pedigree seedlings of 1911 after a severe attack of rust, showing the effect of crossing A7-83ona female plant (A2-23) of average resistance 52 XVII. Pedigree seedlings of 1911 after a severe attack of rust, showing plants from open-fertilized seed of B32-39, usually quite re- sistant but lacking in vigor 52 XVIII. Effect of rust on asparagus seedlings. Fig. 1. — Seedlings at the south end of a bed at Concord, Mass., in August, 1910, just beginning to rust. Fig. 2. — Seedlings at the north end of the bed shown in figure 1 on the same day, showing the destruc- tion of plants caused by their proximity to a young bed on which cluster cups developed abundantly 52 TEXT FIGURES. Fig. 1. Diagram showing the comparative yields of individual plants of row Al, season of 1910 19 2. Diagram showing the average height of 87 progeny rows of seedlings of 1910 in greenhouse 43 3. Diagram showing the height of 50 seedlings each from A7-25 polli- nated with A7-I9 (male) and A7-83 (male), seed weighing between 0.021 and 0.024 gram 44 4. Diagram showing the effect on greenhouse seedlings of 1910 of A7-19 and A7-83 with respect to the average heights and average rust resistance of progeny lots in comparison with the progeny from open- fertilized seed from the same female plants 50 263 B. P. I.— 771. METHODS USED IN BREEDING ASPARAGUS FOR RUST RESISTANCE. INTSODUCTION. History of asparagus rust. — Asparagus rust (Puccinia asparagi DC), which has caused severe losses to asparagus growers m the United States during the past 16 years, is a native of Europe. Common asparagus (Asparagus officinalis) grows wild over the greater portion of Europe and parts of western Asia and northern Africa. Tliis spe- cies, with several closely allied forms, is the normal host plant of the asparagus rust. There is nothing in the literature of the subject to indicate that the rust is in any way nearly as serious a pest in Europe as it has been in America. The comparative immunity of the crop m Europe is partly explained on the ground that the rust is held in check by its natiu-al enemies and by climatic conditions. The gradual development of resistant varieties in Europe has had sometlihig to do with this apparent difference in severity of attack. Occurrence of rust in America. — The definite occurrence of asparagus rust in America was unknown imtil 1896, when its discovery was recorded by Prof. B. D. Halsted,^ of the New Jersey Agricultural Ex- periment Station. The same year brought reports of its occurrence on Long Island- and in Massachusetts and Connecticut. It is very probable that the rust had been introduced m some way from Europe a year or so previously and had spread without being discovered. Since 1896 it has spread over practically the entire area of the United States where asparagus is grown. It became a factor in asparagus growing in the large fields of California in 1902. Failure of spraying methods in the East. — In spite of the general in- terest and alarm felt by growers and station workers at the sudden appearance and rapid spread of this disease, satisfactory methods of rust control have not been developed for the eastern regions. Smith says : ^ In regard to methods of treatment for the control of the rust it may fairly be said that up to the time of the appearance of the disease in California nothing effective and satis- factory had been developed in other portions of the country previously affected. 1 Halsted, B. D. Garden and Forest, vol. 9, 1896, p. 394. 2 Smith, R. E. BuUetln 172, CaUfomia Experiment Station, 1906, p. 1. 263 q 10 BEEEDING ASPARAGUS FOE EUST EESISTANCE. Many elaborate experiments with sprays have been carried out by different experiment stations, but for various reasons the growers as a class have failed to take up the practice of spraying. Here and there an isolated case exists where a farmer put in a spraying outfit at con- siderable cost and managed to check the rust so as to make his beds continue to yield paying crops. Most growers did not take up this work on account of its extra cost and trouble, either letting their old beds die out (PI. I, fig. 1) or plantmg new fields (PI. II) of such semi- resistant varieties as Argenteuil or Palmetto. Previous attempts at breeding. — Some preliminary attempts have been made to start breeding work to develop resistant strains, but so far as the writer knows none of these attempts have been successful. Smith ^ makes the following statement: A beginning has been made by the writer toward breeding desirable rustproof varie- ties by saving seed of such plants from various States, which is being carefully planted for such a purpose. Quite a collection is already on hand from promising sources. Seed has also been imported from Europe of a number of varieties grown there and plants have been obtained from all of these. The prehminary work on spraying and variety testing brought out the fact that certain European varieties were more resistant to rust than the ordinary strains grown in the United States at the time the rust was introduced. Hexamer ^ in his book on asparagus says : All the cultivated varieties of asparagus are readily affected by the rust, although it has been found that some varieties, notably Palmetto, are less susceptible to its attacks than others. Smith,^ under a discussion of varieties, makes the following state- ment: There is no question that some varieties of asparagus are more resistant to rust than others. This difference appears much more in new beds, planted after the rust out- break started, than in those which existed at the time. So much is this true that in the East the rust problem seems well-nigh solved by the growing of Palmetto aspara- gus, yet in the first years of rust the difference in favor of this variety was slight and often not at all apparent. In 1900 Sirrine wrote that " The fields of Long Island have been watched every year since 1896, with the result that only slight, if any, differences in favor of the Palmetto were to be noticed, except that in some cases it did not succumb as early; " yet at present in the same fields the Palmetto alone remains and is being extensively planted. Mr. William Conover planted a field on his place in New Jersey with three rows of Palmetto, then three rows of Conover's Colossal, alternately, and after a few years the Palmetto was still green when the other variety was practically exterminated so that those rows had to be replanted with Palmetto. There is no doubt whatever that this variety is much less affected and less injured by rust in the long run, even though it does not always appear at first. The Argen- 1 Smith, R. E. Asparagus and Asparagus Rust in California. Bulletin 165, California Agricultural Experiment Station, 1905, p. 95. 2 Hexamer, F. M. Asparagus, Its Culture for Home Use and for Market, 1901, p. 140. 3 Smith, R. E. Op. cit., p. 94. 263 Bui. 263, Bureau of Plant Industry, U. S. Dept. of Agriculture. Plate I. w^^^^^^ ^■^'" *^^^^ tl ^^^^E^'.'-" ...^imm^ ' "'"■ -■^■^f.v. Fig. I.-An Asparagus Field on Cape Cod, Mass., Killed out by Severe Attacks OF Rust and Never Replanted. Fig. 2.— Field Showing the Effect of Rust on a Nonresistant Variety of Asparagus. Row B24 (in the Center) would have been as Vigorous as THE Rows on Either Side, but for Rust. (From a photograph taken September, 1908, after the second season's growth.) EFFECT OF RUST ON ASPARAGUS. Bui. 263, Bureau of Plant Industry, U. S. Dept. of Agriculture. Plate II. ^m I H CO IXl qU. INTKODUCTION. 11 teuil (Bonvallet's Giant, French, and other trade names) is, if not identical with Palmetto, indistinguishable from it, and equally rust proof. Among all the American varieties no great difference exists, and they are in fact probably all selections from the old Conover's Colossal. * * * In a rusty field of any variety plants can be seen here and there which are greener, less affected, and more nearly rust proof than the average of the field. - Massacliusetts Asparagus Growers' Association. — The publication in 1905 of Bulletin 165 of the California Agricultural Experiment Sta- tion by Prof. Ralph E. Smith, demonstratuig the value of spraying and preventive measures in fighting rust, reawakened the interest of eastern growers. The general interest in plant breeding at this time, particularly in its application to the breeding of disease-resistant varieties of crops, suggested the possibility of its application to aspar- agus in fighting the rust. The fact that individual plants of a variety as well as different varieties as a whole varied in then* rust resistance showed that the breeding proposition was not impossible. These facts led in 1906 to the organization of the Massachusetts Asparagus Growers' Association, with the object of securing by plant breeding a rust-resistant variety of asparagus. This association enlisted the cooperation of the Massachusetts Experiment Station and the United States Department of Agriculture. A cooperative plan of work was drawn up, under which, with some modification, the work has been carried out. The Department made collections of seed and plants from various sources and furnished the services of its experts in carry- ing out the breeding work. The Massachusetts station furnished the funds to run the work at Concord, Mass., where a branch experiment station was established on the farm of Mr. Charles W. Prescott. Beginning with the fall of 1908, the department has borne all of the expenses in connection with the breeding work, the funds formerly supplied by the Massachusetts station being needed for the proper development of the fertilizer and nutrition work on asparagus at the Concord station. It must be understood at the outset that this work was intended to develop a rust-resistant strain of asparagus and not to discover remedial measures to help the nonimmune varieties already growing. Spraying treatments, etc., have been recommended by plant pathol- ogists for years, but none have been generally adopted by the growers. The Massachusetts Asparagus Growers' Association started out with one idea, namely, the production of a strain that would be so immune to rust that the farmer would need to pay no attention to fighting the disease. This object has been kept constantly in view, and at present the prospect of success is so certain that no experiments with sprays will be undertaken. Nine out of ten growers in the East will not spray, anyway. Breeding work will produce better yielding types of commercially rust-immune asparagus, which will drive out the older fields as fast as it is possible to produce the stock. 268 12 BEEEDING ASPAKAGUS FOR RUST RESISTANCE. PRELIMINARY WORK. NATURE OF THE DISEASE. In taking up breeding work for disease resistance, a knowledge of ^ the life history of the organism causing the trouble is usually con- sidered necessary. Previous work done in America on the life his- tory of the asparagus-rust fungus by Halsted, Stone, Smith, and others has given us a basis of sufficient breadth to go ahead without further work. As a matter of fact, the methods of breeding used in this work have not depended on a knowledge of the life history of the rust fungus, except in a minor way. As yet we have found no constant differences in structure or physiology between the resistant and nonresistant plants. Asparagus rust was described in 1805 by De Candolle as Puccinia asparagi. It belongs to the order Uredinese, which comprises the group of fungi known as "rusts." These fungi are aU parasitic on the higher plants, the most familiar examples being the common grain rusts. Asparagus rust differs from the grain rusts in being autoecious — that is, all stages of the rust occur on the asparagus plant, while the grain rusts are heteroecious, the spring stages occur- ring on a widely different host, wheat rust, for example, having its spring stage on barberry. The disease known to growers as aspara- gus rust is always the du*ect result of an infection from spores of Puccinia asparagi and, contrary to opinions held by manj'- growers, is not caused by fertilizers, soil or weather conditions, insects, or any- thing else of this nature. However, once the disease is introduced, these other factors may influence its development and intensity. The first activity shown in the spring by the rust occurs about the same time that the shoots of asparagus begin to appear above ground. At this time the resting spores of the fungus begin to germinate. From each ceU of these spores there arises a short segmented filament, bearing four smaU sporidia. These sporidia are carried by ah or water into contact with the young shoots just coming through the ground and on germinating send their mycelium through the epi- dermis of the shoot and establish themselves in the asparagus shoot. This mycelium after a growing period of less than a month, varying with weather conditions, starts to produce spores. These spores are located under the epidermis in groups commonly known as cluster cups or gecidia (PI. Ill, fig. 2). These secidia finally rupture the epi- dermis of the asparagus shoot and the light-orange spores are liber- ated. Accompanying the cluster-cup stage on asparagus are found honey-yellow spots of smaller size, known as spermogonia. These spermogonia produce small sporelike bodies that resemble the male spores of related orders, but which are now apparently functionless. 263 Bui. 263, Bureau of Plant Industry, U. S. Dept. of Agriculture. Plate III. Fig. 1 .— Teleutospores of Asparagus Rust. Near the Center of the Cut on THE Right is a Uredospore. X180. FiQ. 2.— Cluster-Cup Stage of Rust on an Asparagus Stem, x 3. DIFFERENT STAGES OF PUCCINIA ASPARAGI. Bui. 263, Bureau of Plant Industry, U. S. Dept. of Agriculture. Plate IV, Asparagus Branch with Sori of Puccinia asparagi in Uredo and Teleuto Stages. X5. PEELIMINAEY WORK. 13 The spores from the chister cups are usually roCiiided, orange yellow, and 1-celled. They are carried by an- currents and lodge on the stems or cladodes of the asparagus plants. These spores germinate in the presence of moisture and produce a mycelium which gi-ows mto the asparagus plant through the stomata or breathing pores. These spring spores provide the infection which causes the summer rust or uredo stage. It is in this stage that the serious damage is done. The first signs of summer rust appear in about two or three weeks after the development of the cluster cups. The -uredo spores appear in clustei"s of single-celled, red-brown spores which rupture the epidermis and are carried away by the ah currents to reinfect other plants. At this stage the rust spreads rapidly. In warm weather accompanied by dew at night, the life cycle from uredo spore to uredo spore is often less than 12 days. This is shown by observa- tions on seedling asparagus plants in the summer of 1909, when rust was repeatedly found on shoots that had been out of the ground less than 12 days. Beginning its attacks in the region of Concord about the latter part of June or first part of July, the uredo stage continues into October. Accompanying it and sometimes occurring alone is the teleuto stage (PL III, fig. 1), the fall stage, which goes through the winter to provide the spring infection. From the common name, fall rust, it might be assumed that this stage would be found only in the fall, but it has appeared regularly with the uredo stage at Con- cord durmg the summers since 1908 (PI. IV). This is due to the fact that it appears under unfavorable circumstances, such as dry weather or prolonged periods of cool weather. Asparagus rust has an active parasite m the fungus Darluca flum , a parasite of rusts in general, which is usually present in the rusted fields and is found attackmg the rust in all its stages. During foggy or rainy periods m summer when the rust suffers most from Darluca, its attacks are reenforced by several saprophytic fungi, which often give a mildewed or molded appearance to shoots that have been mjured by rust. EFFECT OF THE DISEASE. While the effect of asparagus rust is not seen directly in the mar- keted product, nevertheless it is quite injurious. The damage is due to the weakening of the plants by the attacks of the rust on the shoots during the summer after the cutting season is over. It is during the gromng season that the plants store up food for the next spring, and if the shoots are injured or broken off the next season's food supply is accordingly diminished. When the rust attacks a plant no injury is apparent until the formation of the spore clusters ruptures the epi- dermis and allows excessive evaporation from the stems. The shoots 263 14 BREEDING ASPARAGUS FOR RUST RESISTANCE. then wither and die. Attacks on the smaller branches and cladodes show a deadening effect shortly after the rust sori appear. On the whole the mechanical injury seems to be greater than any other. The attacks on young shoots in the late summer when the rust has become abundant are apt to be quite severe. This is due to the almost com- plete mfection that takes place omng to the large number of uredo- spores blowing about while the growth is quite tender just as it comes through the soil. Spores are often developed from these infections before the shoot has had time to branch out and produce cladodes. These spore clusters or sori often are so numerous that they crack off the epidermis from large areas and the plants rapidly wither or stop growing. COLLECTION OF VARIETIES. The first work in starting breeding experiments was the accumu- lation of a collection of varieties from different sources. It was the aim to include in this variety test all possible sources of rust-resistant plants. In order to get the work started as soon as possible, eight rows of yearling roots were planted on the trial grounds at Concord, Mass., during May, 1906. These roots were contributed in lots of 100 by local members of the Asparagus Growers' Association, as shown in Table I. Row 9 was added the next season from roots obtained by Mr. Prescott. Table I. — Roots planted for breeding experiments in field A. Row. Variety. Source. 1 Set May 5. 1906: Anson Wheeler, Concord, Mass. 2 Do Do. 3 F. E. Foss, Concord, Mass. 4 Do Do. 6 Palmetto (Long Island grown) Anson Wheeler, Concord, Mass. 7 Do. 8 Wilfrid Wheeler, Concord, Mass. 9 Set April 17, 1907: W. H. Rseve, Mattituck, Long Island. During the fall and winter of 1906 a larger collection of seed and roots was obtained from most of the seedsmen in America and Europe and from interested growers in the asparagus region of the East. Mr. C. W. Prescott made a trip in the fall of 1906 through the aspara- gus regions of Long Island and New Jersey, securing seed from resist- ant stocks and fields. These lots of seed from all sources were ger- minated in flats in the greenhouses at Washington, D. C, in March, 1907; shipped to the field at Concord, Mass., in May, 1907; and planted in their permanent place in the trial rows. This treatment 263 PRELIMINARY WORK. 15 was very severe and many plants failed to grow. Judging by the resistance and vigor of the plants in 1907, larger orders were placed that fall for seed of Late Argenteuil from Vilmorin-Andrieux & Co., of Paris, and for Reading Giant from Sutton & Sons, Reading, Eng- land. These lots of seed were grown in 1908 at Concord and were planted in 1909, 2^ acres of Argenteuil and practically the sam.e of Reading Giant. No new strains have since been planted. Table II shows the varieties planted in 1907 from the seed and roots obtained the previous fall and winter. It was the intention to have about 100 seedlings or about 10 roots from each lot. Table II. — Asparagus varieties planted in field B at the Concord Asparagus Experiment Station. Row. 90 92 94 96 98 100 102 104 114 Name of variety. FKOM SEEDLINGS GROWN AT WASHINGTON. Dreer's Eclipse Palmetto (Prescott 10) Hub Moore's Giant ...do Palmet to Mammoth Prolific Donald's Elmira Colossal Rust Resistant Colossal Perfection Seedling Late Argenteuil Vick's Mammoth Sutton's Perfection Reading Giant Early Argenteuil Barr's Canadian Mammoth Emperor Barr's Mammoth Columbian Mammoth White. . . ....do White German Erfurt Giant White Snow Cap Giant Giant White Head Barr's New White Sutton's Giant French Snow Head Glory of Biimswick Palmetto Batavian Purple Dutch J'rench Giant Erfurt Giant Bonvallet's Giant Early Argenteuil (Prescott 14). Giant Argenteuil Palmetto Palmetto (Prescott 12) Palmetto (Prescott 2) Palmetto ( Prescott 3 ) Palmetto ( Prescott 4) Palmetto ( Prescott 5 ) P.onvallet (Prescott 13) , Bay State , Palmetto ( Prescott 1 ) Palmetto ( Prescott 6) Palmetto (Prescott 7) Palmetto (Prescott S) Palmetto (Prescott 9) , Pal metto ( Prescott 11) , Nutmeg state Source. Henry A. Dreer, Philadelphia, Pa. Walter Van Fleet, Little SUver, N. J. Joseph Breck & Sons, Boston, Mass. Schlegel & Fottler, Boston, Mass. W. W. Rawson & Co., Boston, Mass. J. M. Mitchell, Mount Pleasant, S. C. Moore & Simon, Philadelplila, Pa. Jolmson & Stokes, Philadelphia, Pa. J. M. Thorbum & Co., New York, N. Y. B. R. Tillman, Trenton, S. C. Jas. Barr & Sons, London, England. H. W. Buckbee, Rockport, 111. R. P. Wakeman, Southport, Conn. Mlmorin-Andrieux & Co., Paris, France. James Vick & Sons, Rochester, N. Y. Sutton & Sons, Reading, England. Do. Vilmorin-Andrieux & Co., Paris, France. Barr & Sons, Loudon, England. James Carter & Co., London, England. Jas. Barr & Sons, London, England. D. M. Ferrv & Co., Detroit, Mich. J. M. Thorljum & Co., New York, N. Y. Vilmorin-Andrieux & Co., Paris, France. Ernest Senary, Erfurt, Germany. Do. Hememann, Erfurt, Germany. Jas. Barr & Sons, London, England. Sutton & Sons, Reading, England. Platz & Son, Erfurt, Germany. Ernest Penary, Erfurt, Germany. N. L. Willet Drug Co., Augusta, Ga. James Carter & Co., London, England. Vilmorin-A.ndrieux & Co., Paris, France. Jolmson °1 UJ UJ I- "- Z t UJ Q O Bui. 263, Bureau of Plant Industry, U. S. Dept. of Agriculture. Plate VI. Types of Asparagus Shoots. Nos. 1 and 3, Good; No. 2, Too Large at Base; No. 4, Rough with Projecting Scales; No. 5, from Short Slow-Growing Plant. PRELIMINAEY WORK. 17 be called Giant; another lot may have more white plants and there- fore may be given the name '' Wliite" or some similar term. The observations at Concord showing lack of uniformity in varieties correspond to those of many experimenters and growers elsewhere who have written on the subject. Ilott/ writing from the standpoint of an English grower, says: There are many so-called varieties, yet they differ but little. Messrs. Sutton & Sons of Reading have two — Perfection and Giant French — which are somewhat dis- tinct. They are both excellent kinds, but whether fchey differ from others going by different names I do not know, for culture has a great deal to do with the appearance of asparagus, as of human beings. A variety which is sometimes well grown, and sometimes the reverse, varies much in appearance, thus favoring the idea of a differ- ence of variety. Two other possibly distinct varieties are Argenteuil Early Giant and Argenteuil Late Giant, which latter probably keeps longer in the cutting season by furnishing shoots later than the first named. Conover's Colossal is another good kind, but not superior to those named above. Palmetto reached me a few years ago with a startling character. It is said to be both earlier and larger than any other, but planted side by side with all the kinds above mentioned I have not yet found it [to] display its alleged virtues. It came from America, and it is possible that it went over there first from Europe, probably from England, for I find it about as good as many others. As to size, it is smaller than Sutton's Giant French. The only other variety which I am going to mention is one which was sent out by Messrs. Bun- yard. They named it Harwood's Early, and it is noteworthy as being alleged to be the earliest to become fit for the markets. It certainly has in my experience for three years in succession started before the other kinds. There is, however, as I consider, far more importance in soils, sites, and general cultivation than in differ- ence of variety, and whereas the cultivation differs materially, the varieties do not, in any great measure, differ from one another. H. W. Ridgway,^ of Swedesboro, N. J., one of the best growers in the East, in a recent discussion of asparagus growing, says : Variety is the principal thing, but in making our selection of variety let us not put too much dependence on the name. It may be misleading, owing to the fact that many growers are not acquainted with the varieties and accept the name given them without questioning its authenticity. There is only one species and several varieties; one-half of the names that wo hear are not varieties. The grass so named has been caused by methods of cultivation, highly-manured land, and climatic condi- tions, and differ from each other only by a single characteristic which will rapidly disappear when grown under climatic and soil conditions different from that in which they originated. Smith in his work in California found no uniform varieties and many names applied to strains that differed from each other in no appreciable way. The same opinion as to varietal differences is held by most growers who have been interviewed. One thing is apparent in looking over tests of varieties, namely, that no real pedigree breeding has been done. A search through 1 Ilott, Charles. The Book of Asparagus, 1901, p. 2. 2 Ridgway, H. W. Extract from Thirty-sixth Annual Report, New Jersey State Board of Agriculture, 1909, pp. 11 J-115. 263 18 BEEEDING ASPARAGUS FOR RUST RESISTANCE. available literature reveals no pedigree work nor even plans for any. The variability of the best imported strains seems to settle the matter (PI. VI), at least as far as Europe is concerned. The results from one generation of pedigree breeding at Concord show that uniformity can be obtained in many characters by proper selection of parent types, yet it is highly probable that little real advance in asparagus varieties has been made since the time of the Koman gardener who grew stalks of such size that three weighed over a pound. A quotation from Hexamer ^ shows the best method recommended by authors in giving advice as to seed growing. This method is practically the same as that recommended by most European writers and is that followed by some of the best growers in this country. In order to insui'e the production of the very best asparagus seed a sufficient number of pistillate or seed-bearing plants, which produce the strongest and best spears, should be selected and marked so that they may be distinguished the following spring when the shoots appear. These clumps should be close together and near some staminate or male plants which have to be marked likewise, as without their presence fertile seed can not be produced. The number of the male to the female plants should be about one to four or five. The following spring all the sprouts of the selected male plants are allowed to gi'ow without cutting. On each hill of the female plants the two strongest and earliest stalks are allowed to grow, cutting the later appearing spears with the others for market or home use. Thus these early stalks of both niale and female plants bloom together before any other stalks, and the blooms on the female plants will be fertilized with the pollen of the selected male plants. This last is of prime importance, for on proper fertilization depends the purity of the seed as weU as the vigor of the resultant plant. Not all seed of even a good plant properly fertilized should be used for reproduction, as of the seeds gathered from any plant some will be better than others. Only the largest, plumpest, and best-matured seeds should be used, for by saving these the most nearly typical plants of the sort will be most certainly produced. The selection of the best seed from typical plants is as essential to success as are good soil, thorough cultivation, and heavy manuring. VALUE OF UNIFORMITY. The uniform distribution of good asparagus over the field is a matter that has received some attention from growers. The yield and type of the individual plants in most varieties differ widely, and it is probable that less than half of the plants pay a profit. This differ- ence in ^deld is illustrated graphically in figure 1. A separate record was kept of the cut of each hill in row Al, New American, Geneva- grown stock, in its fifth season in permanent place in the bed. The diameter of each stalk was measured, tliis method being considered more reliable than to take the weight. This diagram shows that 37 of the hills cut above the average and that unquestionably many plants in the row were not paying for ground rent, fertilizer, and labor. > Hexamer, F. M. Asparagus: Its Culture for Home Use and for Market, 1901, p. 27. 263 PKELIMINAEY WOEK. 19 This row represents an " aver- age" lot of plants. Some beds in Concord and vicinity show a higher average effi- ciency, but many are lower. INTRODUCTION OF UNCULTI- VATED SPECIES. In connection with the in- troduction of asparagus vari- eties for the rust -resistant work, several wild species have been brought in by the Office of Foreign Seed and Plant Introduction from dif- ferent regions for distribu- tion. Asparagus (Aspara- gopsis) virgatus from South Africa was tested at Concord in 1908 and proved to be en- thely free from rust. The following winter aU the plants were killed by cold. Later trials at Washington have shown that this species is quite tender. Mr. George W. Oliver, of this Bureau, has tried to cross this species with A. officinalis, but with- out success. A. officinalis pseudoscaher was tested in 1911 at Concord but proved quite susceptible to rust. So far the attempted crosses be- tween this variety and the parent form have failed to give hybrid plants. A. da- vuricus, a related form from China, was pollinated in 1911 with A. officinalis pollen and has given seedlings that show hybrid characters. A. davu- 263 k Z ', 1 S ^ /i 7C/T 1.20 1.69 S.67 2.33 .13 -97 I.S^ .03 2.'6 .23 3i& I.S6 4.42 8.T2 1 .73 1 .66 S.SO .72 .4S .34 2.3S I.9S 1 .23 .38 .03 2.70 1.3/ S.39 .64 .83 S.06 ■ 72 S.6I 1.46 .78 6.14 4.SS .53 4.63 .20 /.80 3.33 .86 .42 3.8e £.27 i.ao .19 S.02 3.66 .30 .oa ■4 36 2 31 .06 S£8 /.ea 2.eo .36 .83 .66 .03 2.45 .06 3.08 /0.02 .70 /.73 3.13 2.34 3.14 4.33 .78 1.73 1.78 e mm s e 7 e 3 m II 12 13 /■* IS 16 17 IS 19 zo SI 12 Z3 S^ es ?e 27 23 2S 30 31 32 33 34 3S 36 37 30 33 <>/ 'M If ■*y 16 47 fS .SO J> S2 S3 S4 SS S6 i^""' --- M ^sm^m 1 1 ^^^BHHi ^^i^^m IB ^iHBMni HB m^mi^^ WKmmamm Biwwyini irnHTin lOBI m mm ^ammm B ^B ^i^i^H^H aBflsia Mi^i^^H ■■■■ IPSH^KaH IBBaHH ■H^B^ ■SBeaa miB^HH m ■■ \ 1 1 - ■KMHMBI wBw^^mamm 1 H^I^IBa^H BHB ■ S7 se S3 CO ei e-a 63 64 6S 66 67 6B 69 70 7/ 72 73 7t 7S 76 77 70 73 eo 31 Q2 83 84 es 86 87 66 ea so amessa 1 m BB mm 1 BO^E^BG ■B j B ■■ m^iHa ^^^^n 2.63 2.SS .64 3.08 .S3 ./4 .66 2.SS 2.38 .67 1 1 &^ ■B 1 ■1 iiif't U 1, Fig. 1.— Diagram showing the comparative yields of indi- vidual plants of vovf Al, season of 1910. The yield is shown in the sum of the squares of the diameters of the stalks cut from each hill. 20 BREEDIlSrG ASPARAGUS FOR RUST RESISTANCE. ricus has not been tested for rust resistance. Its size and hardi- ness indicate that valuable forms might possibly come from hybrids between it and A. officinalis. A collection of forms of asparagus from all over the Old World is being made, and as these plants come into bloom hybrids will be made with Asparagus officinalis wherever possible. Of course, many species are not closely related to the cultivated forms and will not give fertile hybrids. These forms will be grown to determine their possible ornamental value and to aid in a systematic study of the group. SELECTION. PRELIMINARY METHODS. The first work of selecting rust-resistant plants was begun in the fall of 1908. At that time no definite information was obtainable in regard to rust-resistant plants. It was not definitel}^ known that the resistance was due to a character inherent in the plant, or to some local condition that rendered the plant immune for that en- vironment or season only. The relative value of a resistant plant in a resistant lot as compared to an equally resistant plant in a lot or strain that averaged more rusty was unknown. Several hundred marking stakes were made from ordmary lath sharpened at one end. These lath can be readily seen at some dis- tance in an ordinary asparagus field. The experimental fields were gone over and every plant showing exceptional resistance was marked. In the fall of 1908 the variety test plats in fields A and B, comprising about 2 acres of different strains, were gone over in this way. Three acres of Argenteuil, Mr. Frank Wheeler's select stock, on the station grounds and several acres on the farm of Mr. Wheeler were also included. This work was repeated in 1909 and again in 1910. In 1909, selections were first made from the new plantings of Reading Giant and Late Argenteuil set out in permanent beds that spring. These beds have been included in the selection areas since that time. Besides some new untested plants, the selections of 1910 included only those plants of past years that had been progeny tested and proved of value as breeders. In 1909 many cross-pollina- tions were made between the select plants of 1908. Eleven hundred of these seedlings grown in the greenhouse were planted on the station grounds in 1910 in four rows with hUls 1 foot apart in the row. These pedigree lots were included in the selections of 1910 and 1911. 263 SELECTION. 21 GREENHOUSE INFECTION. When the plans for rust-resistant breeding work were laid out in the fall of 1908 it was intended that the experimental infection of seedling plants to determine then* relative resistance would be carried on during the winter months in the greenhouses at Y\''ashington. In this way it would be possible to gain a season. For various reasons this plan proved impracticable. The rust is not readily transferable in the greenhouses, owing to the lack of dew. The fact that ure- dospores do not germinate unless properly ripened on the host is another factor. During the fall of 1908 and again in 1909 the rusty plants brought into the greenhouses died back, so that the rust infection was lost and the new shoots commg up had no rust on them. The feeling that the different conditions of moisture, heat, etc., ex- isting in the greenhouse might cause an entirely different rust rela- tion as compared to that of the field has led to the dropping of this part of the plan. The work is now so far along that the greenhouse infection work is unnecessary. JUDGING RUST RESISTANCE. In the work at Concord the preliminary selection of breeding stock was begun m the fall of 1908 on fields A and B, planted in 1906 and 1907. The plants were marked for rust resistance on a scale of to 10, the zero mark being used for a plant practically nonresistant and at the time of selection showing no green whatever as a result of a strong rust infection, 10 being the mark for a plant having no rust. The intermediate grades were assigned to plants showing in- termediate degrees of infection according to the personal judgment of the observer. Experience in judging amounts of rust is required. The first season's marks are not as accurate as those of later years, because the plant as a whole rather than the rustiest stalk was then considered. The experience of later years has shown that the rustiest stalk in the hill is the best index, as many of the earlier stalks do not rust badly. They become hardened and seem more immune than the shoots that come up when the rust has become prevalent and is giving a strong infection. In making breeding-stock selections in the future no plants will be saved that do not show practical immu- nity to the rust. In connection with the selection work the question was raised by visiting experimentalists as to the reliability of the methods used in marking resistant plants. In order to test the value of the marks assigned, row Al was scored on two successive days, the second marking beginning at the other end of the row from the first so as to eliminate the factor of memory as far as possible. The result of the score is shown in a correlation table (Table III). 263 22 BEEEDING ASPARAGUS FOR RUST RESISTAISTCE. Table III. — Coirelation between two independent gradings of row Al for rust resistance, September, 1911, to test reliabiliti/ of values assigned by obsei'ver. [Coefficient of correlation 0.923±0.013.] Grades. First marking (grades). Fre- quency. Depart- tire 1 2 3 4 5 6 7 8 9 10 from mean. Second marking: 1 4 4 3 7 6 14 9 10 25 2 1 5 2 3 3 4 3 3 1 3 4 2 5 2 1 1 3 2 5 7 2 3 2 1 6 2 7 15 7 + 1 8 8 2 ...... + 2 9 +3 +4 10 Frequency 4 3 4 7 9 5 14 24 10 1 81 Departure from mean . . -5 -4 -3 -2 — 1 + 1 +2 +3 +4 The greatest deviations are in the middle grades, but as these plants are not valuable for breeding parents the high correlation between the grading in the two., sets of observations from a practical standpoint is higher yet. This method of checking up the value of grades as- signed in selection work where the personal equation largely enters should be followed more extensively than it is at present. The ability to accurately judge differences of minor degree adds greatly to the value of the work. RECORD OF SELECT PLANTS. In making selections some permanent record is necessary. Perma- nent stakes in the field are not desirable, on account of the spring cultivation with a disk harrow. In our experimental plats the plants are placed at definite distances apart and a record made of a select plant, -giving its row number and plant number to enable it to be relocated in the spring. Four-foot lath make cheap and convenient stakes which can be seen for some distance in the field. When plants in a cutting bed are to be left for seed, it is necessary to mark them so the cutters will let them alone. PROTECTION OF SELECT PLANTS FROM FROST. On account of late frosts occurring after the selected plants are up a foot or SO, it is sometimes necessary to cover them over night. Manila paper bags are very good for this purpose. When the shoots were covered with moist earth at times when the temperature went low enough to make ice one-fourth of an inch thick, the stalks froze and when the sun came out they thawed out rapidly enough to be killed. At the same time the shoots under the manila bags escaped injury. A peculiar frost phenomenon v/as observed in June, 1910, when a light . 263 SELECTION. 23 frost occurred in the lowest portions of one of the breeding fields. Glassine paper bags, which are used to cover flowering branches on female plants in breeding work, instead of protecting the flowers from frost actually increased the injury, so that the flower buds dropped off under the bags, while the unprotected buds outside remained uninjured. EUST INFECTION TO SECURE SELECT RESISTANT PLANTS. During the past three seasons there has been an abundance of rust during July, August, and September on the experimental grounds at Concord. This abundant attack of rust is necessary to obtain selec- tions of any practical value. The attack of rust should deaden the tops of practically 95 per cent of the young seedlings from standard Argenteuil stock in the seed bed, or in its ravages in a commercial field of good Argenteuil make it possible for a beginner to pick out less than 10 resistant plants per acre as being plainly superior in rust resistance to the other five or six thousand. So far in this work no asparagus plants have been found that will not rust to some extent. There is a -wide difference in susceptibility in different varieties. The old American sorts represented in Con- cord by Moore's crossbred are practically nonimmune, while Argen- teuil and other related European varieties are highly immune, so much so that they are not troubled by rust unless a new bed planted near by is not being cut in the spring. , There is no question that the spread of the rust from one field to another depends on the direction and intensity of air currents. On the experimental field at Concord the prevailmg \vinds are from the northwest. This fact, combined mth the circumstance that the dew dries up last on the northwest side of the plant, makes the heaviest attacks of rust on the shady side. On account of the direction of the prevailing wind at Concord, it is highly advisable to have any infec- tion area on the north or west of the seedling bed to be infected. Once a field has had a good infection of rust and the resistant plants marked, it is not necessary to provide rust in future seasons, as the select plants can be tested by growing pedigree seedlings. In fact, it is not necessary to test the individual resistance of a plant in order to determine its value as a breeding parent. All that is necessary is to test a small lot of its seedlings, CAUSES OF RESISTANCE. Mcidial stage on resistant plants. — An interesting feature of the rust-resistant breeding work developed in the spring of 1909, when the cluster-cup stage of the rust appeared. The plants that had been selected as rust resistant in 1908 were allowed to grow without bemg 263 24 BEEEDING ASPARAGUS FOR RUST RESISTANCE. ,ciit. In addition to these selected plants several nonresistant plants were allowed to grow up to be used in crossing tests to determine the dominance of the resistant character. No uniform differences in the secidial infection could be noticed, many of the most resistant plants havmg a better infection than the rusty plants. This development caused some doubt as to the nature of resistance and made it seem possible that the immunity of the year before might be due to some temporary factor. Later in the season when the summer stages of the rust appeared this doubt was dissipated, as the resistance again appeared in the select plants of the year before in about the same degree as in the previous season. Relation of structure to resistance. — The fact that sporidia from ger- minating teleutospores can infect through the epidermis without necessarily entering through the stomatal openings gives an explana- tion for the phenomenon just noted and sheds a possible light on the «ause of rust resistance m asparagus. It is a well-known fact that in the heteroecious rusts the secidial stages occur on plants widely different in general character from their hosts when in the uredo or teleuto stages. Thus there is reasonable ground on which to oppose the theory that rust resistance is due to structural differences simply because the gecidial stage appears on resistant plants as freely as on nonresistant ones. However, the theory that in asparagus resistance has a morphological cause is reen- forced by several other points. While little work has been done on this problem in asparagus, the evidence tends to show that resistant plants have smaller stomata than the nonresistant ones. It may be, of course, that the size of guard cells is not closely correlated with the actual size of the opening through which the mycelium must pass, but it gives a suggestive point of attack in solving the problem. When the rust develops in a field in summer, the shoots that came up first and have fully matured and hardened develop a lighter attack of rust than the shoots which appear during the'heightof the rust epidemic. Once the rust gets started in the plant it goes ahead in its development equally well in resistant and rusted plants, no difference being discernible in the ty])e or vigor of the individual sori on plants of different degrees of resistance. Ward,^ in liis studies of rust resistance in the genus Bromus, comes to the conclusion that resistance is not due to structural causes. He says: ^ We are hence driven to conclude that the factors which govern predisposition on the one hand and immunity on the other are similar to those which govern fertility and sterility of stigmas to pollen * * *. 1 Ward, H. M. On the Relations between Host and Parasite in the Bromes and Their Brown Rust, Puccinia Dispersa (Erikss.). Annals of Botany, vol. 16, 1902, pp. 233-315. 2 Ward, H. M. Op cit., p. 314. 263 SELECTION. ' 25 In a later study of rust resistance Ward * says tha this researches '' clearly led to the conclusion that the matter has nothing to do with anatomy, but depends entirely upon physiological reactions of the protoplasm of the fungus and of the cells of the host." Until sufficient evidence has been accumulated on the correlations between structure and rust resistance in asparagus the writer does not care to claim definitely that the size of the stomata is related to the phenomenon of resistance to the attacks of the uredo stage of the asparagus rust. The presence of the aecidial stage on the asparagus plant gives a point of attack in the search for the cause of immunity that is not found in the hetercecious rusts of grasses, and when the studies on this point have been completed it is hoped that new light, at least, will be thrown on the question of disease resistance. Relation of vigor to resistance. — The theory that vigor of growth is correlated with resistance, as suggested by some American writers on the subject, can not be accepted, for many resistant plants are quite small and never produce strong shoots. The trials of the last two seasons of two equally resistant strains of Argenteuil stock from local growers at Concord show no relation between resistance and vigor. About 450 one-year-old seedhngs of each strain were planted in 1908 side by side on uniform land and under uniform treatment. When they were cut for a short time in 1910 each day's yield was separated into giant and common grades, using the local grading system. One lot gave a total yield over a period of 35 days, from April 23 to May 28, of 142-j^ pounds divided into 106y| pounds of giant and 35f pounds of common. The second lot gave in the same period only 65y| pounds total cut divided into 14i pounds giant and 51 3^ pounds common. The details of the record are presented in Table IV. » Ward, H. M. Recent Researches on the Parasitism of Fungi. Annals of Botany, vol. 19, 1905, p. 21. 263 26 BEEEDING ASPARAGUS FOE RUST RESISTANCE. Table IV. — Yield from jive 300-foot roivs of Argenteuil asparagus, showing comparison of large and small strains, seasons of 1910 and 1911. Large strain. Small strain. Giant. Common. Giant. Common. Date. Weight. 03 Weight. s M'Cight. Weight. o i o O a o a a O o 1 a o 1910.1 April: 23 1 1 5 6 14 7 5 11 7 S 4 4 6 4 6 3 2 3 14 13 10 2 7 6 10 3 2 10 1 10 15 12 15 4 20 20 55 63 126 73 45 96 70 72 38 45 55 42 71 40 31 31 2 1 2 2 1 3 2 2 1 2 2 6 3 1 • 2 1 8 9 8 4 S 2 4 2 5 6 5 10 4 2 1 6 5 15 15 19 57 34 65 45 29 73 74 66 35 66 60 54 90 48 51 55 1 1 1 1 8 13 10 14 9 12 10 5 14 15 10 13 7 8 7 8 5 7 11 9 23 20 9 9 16 25 12 8 10 6 7 6 6 4 1 2 2 6 2 1 4 3 4 2 2 3 2 4 2 1 2 11 3 1 1 5 8 11 4 12 7 15 13 13 14 2 3 9 1 20 25 29 27 61 2S 76 May: 2 182 4 60 10 41 13 135 16 120 18 142 20 91 21 108 23 123 24 101 25 146 26 85 27 50 28 69 Total 106 13 1,073 35 12 936 14 8 188 51 5 1,739 1911.2 May: 6 G 8 15 21 25 16 12 8 10 8 "9 8 11 8 S 1 8 7 13 9 7 5 7 6 8 4 6 5 3 5 7 4 4 2 11 10 9 5 8 7 10 3 1 13 4 3 3 10 9 5 3 14 14 9 7 4 6 6 2 12 4 9 14 10 12 13 10 71 82 127 189 211 142 99 72 89 67 83 74 58 103 77 74 13 79 72 121 89 60 48 (■>0 53 80 48 62 51 30 59 67 40 47 30 3 3 3 4 3 2 1 2 2 2 2 2 1 3 5 2 1 1 5 5 4 3 3 2 3 2 1 1 1 2 4 3 1 1 5 7 8 12 8 6 13 8 7 7 10 13 7 8 1 8 10 10 13 1 10 13 3 5 8 6 11 13 14 3 9 4 5 1 11 10 82 85 86 105 84 61 41 45 61 59 62 80 33 88 117 69 20 42 44 113 140 125 70 S3 67 98 67 56 55 37 67 111 88 20 48 1 1 2 4 4 2 2 2 2 2 1 1 1 2 2 2 3 2 3 2 1 1 1 1 1 2 1 1 1 1 1 1 2 8 4 8 11 4 12 8 11 1 7 9 10 6 9 11 1 6 13 4 10 5 11 11 11 10 11 6 9 7 15 13 2 3 2 22 15 28 51 50 30 34 33 25 30 18 18 17 27 28 23 1 39 34 38 33 16 19 21 9 20 9 18 23 20 20 23 20 16 15 1 4 5 8 8 7 5 2 2 4 5 4 5 2 7 9 5 4 4 8 5 4 3 6 3 3 1 3 3 2 3 5 2 4 2 7 10 10 10 11 2 11 8 1 12 11 . 14 10 5 4 9 3 13 8 14 3 12 3 15 6 14 12 10 9 1 2 6 32 8 153 9 133 10 208 11 233 12 214 13 147 14 65 15 80 16 129 17 132 18 . 132 19 146 20 78 21 192 22 246 23 161 24 23 26 112 27 108 28 224 29 184 30 128 31 101 June: 1 176 2 114 3 108 4 49 5 104 7 113 8 . 103 9 105 10 164 11 . . 50 12 137 14 70 Total 305 10 2,737 100 6 2,519 70 12 845 164 10 4,654 » Total yield in 1910: Large strain— 2,009 stalks, weighing 142 pounds 9 ounces (average weight per stalk, 1.14 ounces); small strain— 1,927 stalks, weighing 65 pounds 13 ounces (average weight per stalk, 0.54 ounce). 2 Total yield in 1911: Large strain— 5,256 stalks, weighing 406 pounds (average weight per stalk, 1.23 ounces); small strain— 5,449 stalks, weighing 235| pounds (average weight per stalk, 0.69 ounce). 2C3 BKEEDING. 27 The results in 1911, showing the yield for a full season, were more conclusive. Again lot 1 was far superior in size and total yield, giving 406 pounds total, of which 305f pounds w^ere of giant grade and lOOf pounds common. Lot 2, while actually producing more stalks in the season, had only 235f pounds total, 70f pounds giant and 164f pounds common. The record for 1911 is also shown in Table IV. If there was any difference, the advantage in rust resist- ance is in favor of lot 2; moreover, about 10 of the best plants were reserved out of lot 1 as breeding parents and the cut is thus perceptibly reduced. In the region around Concord it has been noticed frequently that the poorer parts of the field had less rust when other conditions were equal, so that the apphcation of chemical fertilizers has been held by some farmers to be the cause of the rust. BREEDING. The real work of breeding started m the spring of 1909. Many questions of importance in regard to methods had to be settled, for to a certain extent we were on unknown ground. Asparagus was generally recognized as a dioecious plant, but several writers and observers had suggested that parthenogenetic seeds were sometimes produced. The relative dommance of rust resistance in heredity was uncertain m asparagus. Biff en ^ in his work with disease resistance in the small grains had shown an apparent dommance of suscepti- bility, but in asparagus there is no question at present that the heterozygous forms are intermediate in resistance. The possibility of obtammg a combination between strains that would give first- generation hybrid vigor was unportant, and above all was the hope of findmg two parent plants that would give a highly uniform progeny in rust resistance and vigor. In starting the work a study had to be made of the natural and artificial methods of polUnation. Means had to be devised to control the pollination work so that rehable pedigrees could be established. The paragraphs that follow comprise an account of the observa- tions made and the resulting methods developed and now in practice on the different phases of these problems. SEX. Asparagus officinalis is fimctionally dioecious, but the flowers on both types of plants contain rudiments of the organs of the opposite sex. Under field conditions asparagus apparently requires the aid of insects to secure proper pollination. As a rule, no seed is set with- out the aid of bees and other insects carrymg pollen from the flowers 1 Biffen, R. H. Journal of Agricultural Science, vol. 1, 1905, p. 40; vol. 2, 1907, pp. 109-128. 26.3 28 BREEDING ASPARAGUS FOR RUST RESISTANCE. of male plants to the stigmas of the flowers on the female plants. Hermaplirodite plants occur now and then, but so far in our experi- ments can not be considered a factor in seed production. In the flowers of the typical female plant the rudiments of stamens (PL VII, fig. 2) exists, but the writer has never seen one developed sufficiently to even suggest the possibiHty of self-pollination. On the other hand, the male plants often show a well-developed ovary with style and stigma and sometimes even a typical stigmatic surface. The great majority of male flowers, however, lack a well-developed ovary, the rudiment being about half the size of the normal ovary of the female flower and lacking any stigmatic development (PL VII, fig. 1), the style often being completely abortive. The hermaphrodite plants mentioned above are always of the male type, the flowers being for the greater part pure male in that they lack the complete and func- tional ovary. In one wild male plant examined the flowers at the extremities of the branches were typically female with well-developed stigma and abortive anthers. This male had been used for pollination work in testing rust resistance of select plants. Another hermaphro- dite plant which produced seed that would germinate and make healthy, vigorous plants had many flowers whose ovaries lacked the stigmas. The berries on these hermaphrodite plants are very small and rarely have more than one seed in them. The seeds are usually peculiar in that the seed coats are not entirely developed. The seeds appear mottled black and white, varying from the white of the uncovered endosperm in the smaller seeds to well-covered, entirely black seeds in which the coats have had their normal development and have completely covered the endosperm (PL IX, fig. 1). These small seeds make weak plants and in many cases abnormal ones, but the larger, better developed seeds make healthy seedlings of normal type. As yet these seedlings have not been observed in bloom, so the sex inheritance is unknown. POLLINATION. During the blooming period of 1909 and again in 1910 branches of pistillate plants were covered with paraflin paper bags to exclude poflen-carrying insects (PL VIII). Although more than a hundred of these check trials were made, in no case did any seed set from flowers that opened under the bags. The ovaries would swell and apparently start to develop good berries, but after reaching about one-third of the ordinary diameter they would turn yellow and drop off. The uncovered flowers on the same stem set seed abundantly (PL IX, fig. 2 ) . That tliis failure to set seed is due to a lack of polHna- tion is shown by the large number of seeds secured under bags when 263 Bui. 263, Bureau of Plant Industry, U. S. Dept. of Agriculture. Plate VII. Fig. 1.— Male Flowers, the Lower with Some of Its Perianth Lobes Removed TO Show the Stamens and Rudimentary Ovary. The Perianth Lobes are Longer than in the Female Flower, x 5. Fig. 2.— Female Flowers, the Upper with Some of Its Perianth Lobes Removed TO Show the Ovary and Rudimentary Stamens. The Perianth Lobes are Shorter than in the Male Flowers, x 5. FLOWERS OF ASPARAGUS OFFICINALIS. Bui. 263, Bureau of Plant Industry, U. S. Dept. of Agriculture. Plate VIM. Female Asparagus Plant with Branches Covered by"Glassine" Bags to Keep Insects from Pollinating the Flowers with Pollen from Unknown Males, This Plant Being Used to Test the Comparative Resistance Transmission OF Several Males. Bui. 263, Bureau of Plant Industry, U. S. Dept. of Agriculture. Plate IX, C3 I- O CO ^^^< LL O < (-) LI. L_ UJ '-^ UJ CO UJ ^ O I o z z o - CO ^ I o H I- o 2 o c5 ta . liJ Q. Z « I- "- - u ro L_ CC CO UJ 55 oQ 17^ cc > a (E H < ^ UJ CQ UJ Q- CO > I- ^2 CE o _ < '. § CO ^ ll