casin is located under semiarid or average dry-land conditions in the Judith Basin and has a normal annual precipitation of 16.51 inches. Havre is under marginal dry-farming conditions in the so-called "Triangle" section and has a normal annual precipitation of but 13.71 inches. Thus, three distinct environmental conditions are represented. The Marquis Hard Federation and reciprocal crosses here studied were made, at the request of the senior writer, by V. H. Florell (8) at Chico, Calif., in May, 1921. The F, material was grown at Davis, Calif., in 1922. The Marquis Hard Federation & crosses were given the hybrid number 21202 and the Hard Federation ? X Marquis crosses number 21203. The first two numerals, 21, stand for the year 1921, in which the crosses were made. The numbers 202 and 203 were assigned to these particular crosses. The F, material was divided. Families 21202 B1, B2, and B3 and 21203 A1, A2, and A3 were sent to Bozeman, Mont., and families. 21202 A1, A2, and A3 and 21203 C1, C2, and C3 were sent to Moccasin, Mont., where the 12 F, families were grown in 1923. 2 In 1923 the hybrid plants at both Bozeman and Moccasin were definitely spaced at 3-inch intervals in rod rows 1 foot apart. Unfortunately, the parent varieties were not sown at Moccasin. At Bozeman the Hard Federation parent was sown identically with the hybrids, but the Marquis parent was sown two days later and under slightly different conditions. In 1924 the F, material was grown at Bozeman, Moccasin, and Havre in nursery rows 1 foot apart. At Bozeman 70 kernels were spaced 3 inches apart in each row. At Havre the seeding was done in a similar manner, but the number of kernels varied somewhat because of the limited quantity of seed available from some of the F, selections. At Moccasin the 1924 sowings were not definitely spaced, but 2.3 grams of seed was used in each of the rows, which were 16 feet long and 1 foot apart. Checks of the parent varieties, sown in the same manner and at the same time as the F, hybrids, alternated in every tenth row at the three stations. The F, strains grown at Bozeman and Havre in 1924 were from F, plant selections from Bozeman in 1923. The F, strains grown at Moccasin in 1924 were from F, selections made at that station the previous year. The material thus grown constitutes the basis for the following study. Probable errors for numbers of individuals where only two classes are concerned were obtained from tables of probable errors of Mendelian ratios prepared in the department of plant breeding of Cornell University, Ithaca, N. Y., from the formula 0.6744898 V p q, in which n is the total number of individuals and p and q the percentages corresponding to the ratios involved. Deviations from the expected which are less than three times their probable errors are not here considered significant. When more than two classes are concerned, the goodness of fit to the expected ratio is determined by the X2 method in which (o-c)2 Χ = Σ From X2 the value of P is determined by interpolation from Elderton's table given by Pearson (14) for determining this The values of P usually are less than 1, which value represents a perfect fit. Ratios having deviations with a value of P lower than 0.043 are not here considered significant. value. Correlations here reported were determined by the product moment coefficient of correlation method in which rzy +0.6745 1- p2 = n Στί noxy Correlation coefficients greater than three times their probable errors are here considered statistically significant. Plant selections were made in the F2 and F, generations from their appearance in the field, their threshed grain, and from each frequency class for date of heading, date of ripening, fruiting period, height, yield, and crude-protein content. The dwarf plants introduced a possible difficulty in maintaining a random sample. The lack of evidence of linkage between dwarfness and other characters, together with the few instances of linkage ever recorded in wheat hybrids, minimizes the importance of this, and the writers feel that the normal plants, as selected, fairly represent a random sample. SEGREGATION OF CHARACTERS IN THE F2 AND F, GENERATIONS The F, plants grown at Davis, Calif., in 1922 were all normal in stature, apically awnletted, brown glumed, and red kerneled. No further notes or comparative data with the parents were obtained in this generation. A study of individual plants for the principal contrasting characters and factors for yield and quality was made on the F, material grown at Bozeman in 1923 and for some of the characters on similar material grown at Moccasin in the same year. The study was continued on F, material grown at Bozeman, Moccasin, and Havre in 1924, to determine the inheritance and the environmental effect on the material under the different representative Montana conditions. The characters studied for their inheritance are dwarfness, awnedness, glume color, kernel color, curledness of leaves, heading period, ripening period, fruiting period, height, yield, and crude-protein content of the grain. The reciprocal crosses were studied to determine the differential influence, if any, on the progeny. Dominance of the curled-leaf character appeared partially reversed in F, of reciprocal crosses. The studies made on this character will not be presented in this bulletin. The results of the studies of the other characters in the F, and F, generations follow in the order listed above. 2 DWARFNESS Dwarf plants appeared in F, progenies of all F, families of the Marquis Hard Federation and reciprocal wheat crosses grown at Bozeman and Moccasin in 1923. At Bozeman some of the dwarf plants headed at a height of about 6 inches and matured seed. At Moccasin, however, only a few produced heads late in the season, and none of them matured seed. The dwarf plants which did not head were similar to the grass clumps first described by Farrer (7). From the results at the two stations it appears probable that both genetic and environmental factors were in part responsible for differentiation into the groups hereafter called dwarfs and grass clumps. At Bozeman there appeared in the F, progeny of six F, families 600 normal plants, 114 dwarfs, and 38 grass clumps; at Moccasin, in the F. 2 progeny of six other F, families, there were 457 normals and 101 dwarfs and grass clumps, the two latter not being distinguishable. These results indicate that two genetic factors are involved, segregating in the F, progenies to give a 13 :3 ratio for normals to combined dwarfs and grass clumps and in a 15:1 ratio for combined normals and dwarfs to grass clumps. As the Moccasin data do not permit the latter separation, the F, data from both stations are tabulated in only two classes-normals compared with dwarfs, the latter including grass clumps. The data for each of the F, families, the totals at each station, and the totals from both stations are given in Table 3. 2 TABLE 3.-Segregation of 1,810 F2 plants of the Marquis Hard Federation wheats and reciprocal crosses into two classes, normal and dwarf plants, when grown at Bozeman and Moccasin, Mont., in 1923 The data show a close fit to the 13: 3 ratio in each F, family and in their totals at both stations. The deviations in numbers in all cases are less than three times their probable errors. There is no consistent or significant difference between reciprocal crosses, as the percentages alternate slightly at the two stations. The study of normal and dwarf segregation was continued in the F, generation at Bozeman in 1924, where F, families were grown from 224 normal and 25 dwarf F, plants. The data obtained from normal plants are given in Table 4. TABLE 4.-Breeding behavior of 13,397 F3 plants_grown from seed of normal Fr plants of crosses between Marquis and Hard Federation wheats, at Bozeman, Mont., in 1924 2 The data show that of the thirteen-sixteenths which were normal plants in the F, generation, approximately seven parts bred true for normal plants and six parts segregated for normal and dwarfs in the F. The families throwing dwarfs were divided according to whether they were below or above 21.9 per cent for the 13:3 and 3:1 ratios accordingly. Of the six segregating parts, approximately four parts bred as in F2 with 13 normals to 3 dwarfs, and two parts segregated in a 3:1 ratio of normals to dwarfs. A very close fit to the 7:4:2 ratio was obtained, P equaling 0.72. Of the four parts segregating in a 13:3 ratio, the deviation is greater than that in F2. This is evidently due to the overlapping with the 3:1 ratio. The deviation of 49 16.30, however, is no larger than would be expected by chance in 1 out of every 22 trials. The two parts segregating in a 3:1 ratio have a deviation of 33±13.01, which is close to the expected ratio, as the deviation is but 2.5 times its probable error. As shown, the percentage of stand for the three types was practically 85 per cent for each, so that it appears certain that the seed of the dwarfs is not less viable than those of the normals. TABLE 5.-Breeding behavior of 934 F3 plants grown from dwarf F2 plants of crosses between Marquis and Hard Federation wheats at Bozeman, Mont., in 1924 |