Inheritance of kernel resistance to Fusarium graminearum in maize

Inheritance of maize (Zea mays L.) kernel resistance to ear rot caused by Fusarium graminearum Schwabe was investigated in generations derived from a cross between resistant (CO325) and susceptible (CO265) maize inbred parents. Parents, F-1, F-2, and backcross generations were evaluated in two locations in eastern Canada in 1993 and 1994. Plants were inoculated with a macroconidial suspension using a kernel-stab method 15 days after silk emergence. Disease severity was assessed at harvest using a seven-class rating scale. Significant differences were observed among the generation means in all environments. In general, the F-1 did not differ significantly from the resistant parent except at one location in 1993. The frequency distribution of the F-2 and backcross generations showed continuous variation. Generation means analysis indicated that resistance to F. graminearum was under genetic control with both simple (additive and dominance) and digenic (dominance x dominance) effects contributing to the total genetic variation among the generation means. Weighted least square regression indicated that more than 68% of the genetic variation could be explained by additive effects. Estimates of the number of effective factors affecting kernel resistance ranged from 4.6 to 13.7.