Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 1, 1996
Publication Date: N/A
'Jasmine 85' (JM85) is highly resistant to all known U.S. pathotypes of Pyricularia grisea except IB-54. 'A-301' is resistant to only race IB-54. JM85 is a potential source of resistance to IB-49 and IC-17. In 1993, some 68-100 F2 plants from the cross A-301/JM85 were inoculated with isolates of races IB-54, IG-1, IC-17, and IB-49 to determine inheritance of resistance. .Resistance to race IB-54 (isolate 429) in A-301 was governed by a single dominant gene (chi-square 3:1=0.02). Resistance to race IG-1 (isolate 74T3) in JM85 was governed either by a single dominant gene (chi-square 3:1=1.58) or by complementary dominant and recessive genes (chi-square 13:3=0.02). Reactions of F2 plants to races IB-49 (isolate 793) and IC-17 (isolate 92T107) were less definitive. In both cases, however, resistance appeared to be a recessive trait. In 1994, the same tests (except with race IB-54) were conducted on populations of 1000+ F2 plants each. Probabilities of the eproposed resistance genes were low and probably reflected some confounding by "minor" genes and microenvironment. In 1995, 324 F3 lines were challenged with each of the three pathotypes. Of the 324 F3 lines, 215 segregated for resistance to all three pathotypes. We speculate that several modifying genes may be involved which render plants lacking major gene resistance to appear resistant. The need for an intermediate resistance class in rating F3 plants supports the existence of these genes. Unequivocal cases of F3 lines differing in reactions to the three pathotypes of P. grisea led us to conclude that JM85 has one dominant and one recessive gene, each conferring resistance to race IG-1, and that the genes conferring resistance to IC-17 and IB-49 are non-allelic.