Inheritance of gray leaf spot resistance in corn
Date
1999
Authors
Cromley, Jason Michael David
Major Professor
Advisor
Hallauer, Arnel
Committee Member
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Abstract
Gray leaf spot of maize (zea mays L.), a disease caused by the fungus, Cercospora zea-maydis Tehon and Daniels, is becoming prevalent throughout the U.S. Corn Belt region. Previous studies on the inheritance of resistance to gray leaf spot have been primarily done in the eastern states and not in the Midwest. The objectives of this research are to 1) estimate genetic effects for five crosses, resistant x susceptible (B98 x B79, B99 x N192, B100 x MS1334), resistant x resistant (B98 x B99), and susceptible x susceptible (B79 x N192), with six generations by using a generation means analysis and 2) estimate the heritability and genetic gain by evaluating 100 S1 progenies in the B79 x B98 cross. Disease assessments were based on visual estimates of percent leaf area affected (PLAA). PLAA means were fit to disease progress models in the calculation of area under disease progress curve (AUDPC).
The range of AUDPC values among the parents were 11.4 to 42.9 for B98 and MS 1334, respectively. Generation mean analyses showed significant additive genetic effects, except for B79 x B98, and dominance genetic effects were expressed by all populations. Nonsignificant residuals indicate that epistatic effects were not as important in these populations. A high broad sense heritability estimate of .78 indicates that selection per se within the B79 x B98 population for gray leaf spot resistance should be effective. Resistance to gray leaf spot in the maize genotypes evaluated was conditioned by both additive and dominance effects with the cross B79 x B98 being highly heritable for gray leaf spot resistance.
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thesis