17. Brittle stalk-2 (bk2). Plant appears normal, but the leaves, stalk, ear, and all parts break easily under pressure. Viability good. Classification good at all stages of development by bending the leaves sharply.
The seed was originally received by the Maize Genetics Cooperation from L. C. Raymond, of Quebec. A test for allelism with bk was negative (News Letter, March 23, 1937, p. 1). Brittle stalk-x (bk-x) reported by Wiggans (News Letter, March 6, 1938, p. 12) proved to be an allele of bk2 (News Letter, April 15, 1939, p. 12).
Bk2 is linked with sh and wx in chromosome 9 as shown by the following F2 data:
| F1 genotype | F2 progenies | |||||
| sh wx + | sh wx + | 29 | sh wx bk2 | 1 | ||
| --------- selfed | + + bk2 | 37 | + + + | 95 | ||
| + + bk2 | sh + bk2 | 3 | sh + + | 11 | ||
| + wx + | 28 | + wx bk2 | 0 | |||
| Total = 204 | ||||||
| sh - wx = 22% | wx - bk2 = 15% | sh - bk2 = 35% | ||||