INHERITANCE AND LINKAGE OF RESISTANCE IN CUCUMBER LINE SMR-18 TO RACE-1 AND RACE-2 OF FUSARIUM-OXYSPORUM F-SP CUCUMERINUM

Studies were carried out on the inheritance of resistance to race 2, a nd the linkage relationship between resistance to races 1 and 2 of Fus arium oxysporum f.sp. cucumerinum in the cucumber cv. SMR-18, as well as on the reactions of several cucumber cultivars to inoculations with race 2. The inbred line Straight-8 (P-1) (susceptible to races 1 and 2 of 1;. oxysporum f.sp. cucumerinum) was crossed with the inbred line SMR-18 (P-2) (resistant to both races). When F-1, F-2, BC1P1 and BC1P 2 progenies were inoculated at the cotyledon stage with a suspension o f spores of F. oxysporum f.sp. cucumerinum race 2, the ratios of resis tant to susceptible plants indicated that resistance was conferred by a single dominant locus. When 158 BC1P1 plants were selfed, and from e ach resulting F-2 family different groups of 12-18 seedlings each were tested for resistance to either race 1 or race 2, segregation data in dicated a complete linkage between the two loci conferring resistance to these by inoculation with F. oxysporum f.sp. cucumerinum race 2, ra ces. Among the 34 cultivars tested at the seedling stage, five were su sceptible, while the remainder were highly resistant.