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- Author or Editor: Stephen L. Grier x
Abstract
AS9 is a sugary-1 breeding population of sweet com (Zea mays L.) having moderate to high resistance to first brood attack (leaf feeding phase) by the European corn borer (Ostrinianubilalis, Hübner). The first sugary-1 source material having such resistance, it has been composited from diverse sources and is being released for its potential value in sweet corn breeding.
Abstract
Procedures for forced field infestation of maize with European corn borer egg masses, placed to simulate possible natural ovipositional sites and to emphasize damage to the ear, were compared. A growth chamber procedure using excised ears and a free-choice (preference) infestation procedure were also used. Forced infestation in the field permitted infestation at a uniform relative maturity and uniform development of borers from time of infestation to evaluation. An ear-and-leaf infestation procedure appeared to be the most appropriate for simultaneous evaluation of kernel damage and stalk tunneling. Estimated heritabilities, using this procedure on 2 segregating populations, were 0.71 and 0.84 for kernel damage and 0.39 and 0.79 for stalk tunneling. Phenotypic correlations among 3 ear damage criteria were noted (r = 0.42 to 0.46). Evaluation based on kernel damage alone, excluding cob tunneling and number of surviving larvae, was considered sufficient. There was no evidence that kernel damage was influenced by level of stalk tunneling.
Abstract
Artificial was compared to natural infestation for evaluating kernel damage and stalk tunneling on maize (Zea mays, L.) caused by European corn borer (Ostrinia nubilalis, Hiibner) larvae. Under conditions of natural infestation, differential damage levels among families were more closely correlated with silk date than oviposition frequencies on the host plants. The association between damage and silk date was reduced following artificial infestation. Artificial infestation, which permits infestation at a common stage of maturity (full silk), a uniform and greater insect population on host plants, and a uniform opportunity for larval development on the ear from time of infestation to time of evaluation, is preferred for differentiating maize genotypes for borer resistance.