Inheritance and Components of Resistance to Bipolaris Maydis Race O (Maize, Corn, Breeding)
Burnette, David Charles
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https://hdl.handle.net/2142/70599
Description
Title
Inheritance and Components of Resistance to Bipolaris Maydis Race O (Maize, Corn, Breeding)
Author(s)
Burnette, David Charles
Issue Date
1985
Department of Study
Plant Pathology
Discipline
Plant Pathology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Plant Pathology
Abstract
Three different studies using the Bipolaris maydis race O - maize pathosystem were done at the University of Illinois in 1981, 1982 and 1983. The first study was a quantitative genetics study of the inheritance of resistance in 12 families derived from inbreds determined to be highly resistant to this fungus. Additive genetic effects were highly significant in all families, accounting for 49.0% to 96.9% of the total variation. Significant dominance effects were detected in all but one family but accounted for only 2.5% to 46.9% of the total variation. Estimates of broad sense heritabilities ranged from 29.5% to 69.1% and the estimated numbers of effective factors ranged from 2.2 to 14.6. The second study was the determination of the optimal time period for evaluation of inbreds and hybrids for resistance. Weekly ratings of disease severity (% leaf area blighted) were taken with inbreds and hybrids. Selection of the optimum rating period was based on the maximum separation of the resistant and susceptible inbreds with a relatively low standard error and the rating occurring before senescence of the plants. Using these criteria, the optimal time period for evaluations of inbreds and hybrids for resistance to B. maydis race O is 18-24 days after anthesis. This technique may be useful for determination of optimal evaluation periods for other diseases. The third study was the measurement of two components of resistance, lesion length and fungus sporulation, with nine resistant and three susceptible inbreds and a number of hybrids derived from crosses among inbreds. Significant differences were observed in lesion length among inbreds and hybrids. No significant differences were observed in fungus sporulation per unit area between inbreds. Measurement of lesion length may be useful for routine greenhouse evaluations of inbreds and hybrids for resistance to B. maydis race O. Measurement of fungus sporulation does not appear to be useful as a routine evaluation criterion.
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