BREEDING 



BREEDING 



551 



it should be stated that it is very easy to find types of 

 plants differing from the varieties or races ordinarily 

 grown, but far the larger part of such variations are 

 worthless types. Good new types, the superior or even 

 the equal of the known varieties, are of very rare 

 occurrence. 



If the general improvement of a variety is the 

 breeder's purpose, he should choose a considerable num- 

 ber of apparently superior plants of good type, which 

 will form the basis of his selection work. Breeders who 

 are conducting careful experiments will find it neces- 

 sary and desirable to use careful methods of judging 

 their plants. While one is breeding possibly for one 

 primary improvement, as, for example, increased yield, 

 it is necessary, at the same time, that one should keep 

 the product up to the standard in other characteristics, 

 namely, quality, disease-resistance, drought-resistance, 

 and the like, and that one sees that all of the good 

 qualities of the variety are retained. To do this properly 

 necessitates the use of a score-card, on which each char- 

 acter of the plant that is important is given its relative 

 weight or grade. By the use of such a score-card, the 

 breeder can judge each character separately, and by the 

 adding up of the score-card get the rank of different 

 plants in a comparative way. 



Inheritance test. When a number of plants have been 

 chosen, the next important factor is to test each indi- 

 vidual as to its inheritance. It must be continuously 

 remembered that a plant is valuable only as it produces 

 good progeny. To determine the inheritance, the usual 

 method is to plant the seed from each individual se- 

 lected in a row by itself, or in a marked part of a row. 

 This is the so-called "plant-to-row" method, and brings 

 the offspring of a single indiv idual together so that they 

 may be readily compared with each other and their 

 qualities carefully judged. These progeny rows should 

 be grown in a special breeding-patch in which the soil 

 is as uniform as can be secured. 



It is frequently found that two select plants that are 

 equally good so far as their yield is concerned will give 

 progeny that, as a whole, differ greatly in this respect. 

 In the progeny of one, almost every plant may have 

 inherited the desired quality, while in the progeny of 

 the other only a few of the plants may show, in any 

 noticeable degree, the inheritance of the quality. To 

 determine the degree of inheritance, it is necessary to 

 grade carefully the progeny of each individual. 



Finally, with the use of his best judgment, the 

 breeder determines the superior progenies, and these 

 would be the ones which have most nearly given the 

 ideal type and produced the best yield of the highest 

 quality. This would end the work of the first gen- 

 eration of the selection as the breeder now has the 

 data which shows him which of the original plants 

 selected was the superior one. It will be seen that this 

 is a method of judging the individual by its progeny. 



Continuation of the selection the second year. 



Having determined the superior progeny or progenies 

 at the end of the first year, the breeder then makes his 

 selections of seed-plants from these best progenies for 

 continuing the breeding. While one progeny may be 

 and usually is superior to all others, this may be due 

 to the season or other accidental conditions and for a 

 few generations it is usually the best policy to make 

 selections from several of the best progenies. Select 

 from each of the superior progenies several of the best 

 plants, using the same care in selecting these plants as 

 was used in choosing the first plants. Preserve the seed 

 from each of these plants separately and keep it care- 

 fully labeled so that its origin may be known. 



The further work with these plants consists in plant- 

 ing each individual by the plant-to-row method, test- 

 ing the inheritance as described in the first generation, 

 and finally selecting again the best progenies. This 

 would be followed by again selecting from the best pro- 



genies a number of superior individuals to continue the 

 selections in the third year. 



The third and succeeding years of the selection would 

 be conducted in the same way as long as it was thought 

 necessary or desirable to continue the work. 



Securing general stock seed of the improved strain. 



In carrying out selection work as outlined in the pre- 

 ceding section, it is ordinarily the object of the breeder 

 to secure an improved strain of the race with which he 

 is working, and usually he desires to utilize such im- 

 provements as he can make at the earliest possible time. 

 With ordinary annual crops such as beans, peas, toma- 

 toes, corn, and cotton, it will be found a good policy at 

 the end of the second year of the selection, after taking 

 the seed from the few special plants used in continuing 

 the pedigree breeding, to harvest the seed from a num- 

 ber of the best plants remaining in the chosen progenies 

 and using this seed to plant a multiplication plat from 

 which stock seed may be secured to plant a fairly large 

 crop. Each year following this, seed may be taken in 

 the same way from the best progenies in the breeding 

 patch to plant a multiplication plat. By this method, 

 seed of a gradually improving grade may be secured 

 for planting a general crop. 



Control of parentage. 



In plant-breeding, as in animal-breeding, the isola- 

 tion of the parents is a very important consideration. 

 It is necessary that the character of both parents should 

 be known whenever this is possible. In breeding plants, 

 more attention is given ordinarily to the mother parent, 



and in very many 



a b c instances the charac- 



ters of the father 

 parent are entirely 

 neglected. Animal- 

 breeders, on the con- 

 trary, give more 

 attention to the char- 

 acters of the male 

 parent, and much 

 improvement in ordi- 

 nary herds has been 

 accomplished by the 

 introduction of im- 

 proved heritage 

 through the male. In 

 plant-breeding, it is 

 desirable that the 

 seed of the select in- 

 dividuals be planted 

 in a field by them- 

 selves. This insures 

 that only progeny of 

 carefully selected in- 

 dividuals will be 

 planted near to- 

 gether, and thus no 



e f a 



642. Aquilegia flowers, illustrating 



the process of emasculation, 

 a, mature bud showing stage which 

 should be chosen for emasculation; 

 6, similar bud with the tips of the 

 corolla pried apart and the stamens 

 removed; c, a bud opened naturally, 

 too old to operate on; d, a bud of the 

 stage shown in a and 6. with corolla 

 removed to show the internal organs; 

 e t a bud the same as in d, but with 

 the stamens removed; /, the same as e, 

 but older, at the age when pollination 

 normally takes place; ff, pistil shortly 

 after fecundation, the remnants of the 

 stamens having fallen away. 



ordinary stock will 

 enter as a contamination. One can be certain that each 

 plant of the progeny is fertilized with pollen from 

 another similarly good plant, or at least from a plant 

 derived from good parentage. One difficulty, however, 

 has been experienced by plant-breeders in planting con- 

 tinuously their selected stock in such isolated plats. If 

 this method is continued year after year, it results in 

 fairly close inbreeding, which, in the case of plants, 

 frequently results in loss of vitality and vigor. In 

 animals there is frequently no noticeable effect from 

 close inbreeding, and many of the most famous animals 

 have been produced as a result of the closest in-and-in- 

 breeding. In plants, however, it is possible to secure 

 much closer inbreeding than in animals, as in many 

 cases a plant can be fertilized with its own pollen. 

 Within recent years, much activity has been shown 



