. Contributions from the Laboratory of Plant Genetics. Feb. 10, 1923 Genetics of Bunt Resistance in Wheat 47i Table IX.—Frequency distribution of resistance to bunt in a cross between Hybrid 128 and Marquis, both of which are susceptible when fall-sown Variety. H X M F2, HXMF3 H X M F4 Year tested. Hybrid 128 Marquis. . J1919. \1920. 1/1919- \1920. 1920. 1919. 1920 Bunt in parent row. Per cent. 63. O 98. I Not tested. 74- 0 Not tested. ...do 75- 9 79-4 83-9 Number falling into class with average percentage of bunt of— s IS 25 35 45 55 65 75 85
. Contributions from the Laboratory of Plant Genetics. Feb. 10, 1923 Genetics of Bunt Resistance in Wheat 47i Table IX.—Frequency distribution of resistance to bunt in a cross between Hybrid 128 and Marquis, both of which are susceptible when fall-sown Variety. H X M F2, HXMF3 H X M F4 Year tested. Hybrid 128 Marquis. . J1919. \1920. 1/1919- \1920. 1920. 1919. 1920 Bunt in parent row. Per cent. 63. O 98. I Not tested. 74- 0 Not tested. ...do 75- 9 79-4 83-9 Number falling into class with average percentage of bunt of— s IS 25 35 45 55 65 75 85 95 2 I 3 1 3 I " 3 m I 1 — .... 5 53 '"l 270 — 1 1 .... 1 I .... 1 I 1 1 1 I 1 I 1 « Seed from a different source, but since Marquis is a variety recently introduced and appears to be constant for all its characters, it is likely that there is no genetic difference in the resistance of these strains, for seed from these same strains planted in the spring produced less than 5 per cent of bunt. The F4 generation shows an average of per cent less bunt than the F3 parent rows, but this is undoubtedly due to seasonal fluctuations, for Hybrid 128 and Marquis showed similar differences in 1919 and 1920. A closer study of the F4's indicates that even in these extremely suscep- tible segregates there is a constant difference in their susceptibility comparable to the differences in the susceptibility of the parents. This is more clearly brought out by the following figures:. From 9 low selections 80. 2 From 4 high selections 96. 8 Difference between high and low 16. 6 62. 2 72. 4 10. 2 Difference. 18. o 24. 4 Out of the 9 low F3 rows (between 75 and 84 per cent bunt) 5 produced the smallest percentage of the 13 rows in the F4 generation. Out of the 4 high F3 rows (between 94 and 99 per cent bunt) selected, one produced the highest amount of bunt in the F4 generation, and two of the others produced more than the average of all the F4's in 1920. This indicates t
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