Luther Burbank, his methods and discoveries and their practical application; prepared from his original field notes covering more than 100,000 experiments made during forty years devoted to plant improvement . it characters that arerepresented in any given fruit or flower. And theessential principle, stated in Mendelian terms, tobe aimed at by the experimenter who would fixa newly developed type of plant so that it willbreed true from seed, must be to render the planthomozygous for the factors of each pair of unitcharacters involved. If that can be done, theplant will breed true; if that canno
Luther Burbank, his methods and discoveries and their practical application; prepared from his original field notes covering more than 100,000 experiments made during forty years devoted to plant improvement . it characters that arerepresented in any given fruit or flower. And theessential principle, stated in Mendelian terms, tobe aimed at by the experimenter who would fixa newly developed type of plant so that it willbreed true from seed, must be to render the planthomozygous for the factors of each pair of unitcharacters involved. If that can be done, theplant will breed true; if that cannot be done, theplant will not breed true. In the olden phrasing, this would be spoken ofas line breeding—a method long familiar toevery breeder of plants or animals. Fixing a Type in the Second Generation In actual practice, where only two or threeunit characters are involved, it may be possibleto produce a new type that breeds true, or is fixed,in the second generation. In such a case the timeelement may be ignored. Take, by way of illustration. Professor Castlesguinea pigs, to which reference has more thanonce been made. Suppose we have as parentstock a black guinea pig with a smooth coat, and [242]. 5 ;< 6 r^ O fd 3 ^— e iS^; S ~ N g S»3g~.0-33S~.3 i=:<< CDre B -, 3 n I:. K^.^O S .c«i a. re s S LUTHER BURBANK a white guinea pig with a rough coat. Now wehave already seen that blackness is dominant towhiteness as regards the coat of the guinea pig,and we must further understand that roughnessof coat is known to be dominant to smoothness. We must expect, then (according to ProfessorCastle), that when a cross is made, the guinea pigsof the first filial generation will, unlike eitherparent, be black in color and rough as to coat. But, in the succeeding generation, the black,rough-coated guinea pigs being interbred, therewill be a certain number of offspring that combinethe dominant characters of blackness and rough-ness of coat, and will breed true t
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