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Evaluation of soybean breeding lines for corn earworm antibiosis

Mebrahtu, T., Kraemer, M., Andebrhan, T.
Crop science 2002 v.42 no.5 pp. 1465-1470
Glycine max, pest resistance, genetic resistance, genotype-environment interaction, larvae, weight, bioassays, genotype, biological resistance, Virginia
Corn earworm (CEW) (Helicoverpa zea Boddie) is the most serious insect pest of soybean [Glycine max (L.) Merr.] and often has reduced yield in much of the Mid-Atlantic and southern coastal plain of the USA. The objectives of this study were to determine the magnitude of genotype x year interaction (GYI) of antibiosis to CEW and to identify genotypes with stable performance. Thirty-two soybean breeding lines, including two susceptible and one line resistant to CEW, were planted in single row plots arranged in a randomized complete block design in 1996 through 1998 at Petersburg, VA. Petri dish assays were used to evaluate terminal foliage of field-grown soybean for resistance to CEW. Data were analyzed by means of genotype x year analysis of variance (ANOVA) and cultivar superiority performance measure (CSPM). Even though there was considerable variation among the genotypes tested during the three growing seasons, genotypes that ranked consistently either lower or higher in mean CEW larval weight were found. Among the genotypes tested, V89-2623, VS94-42, and VS94-27 generally had the highest CEW larval weight, whereas VS94-11, VS94-12, and VS94-26 were consistently in the lowest CEW larval weight group. Results suggest that CEW resistance of these latter three lines is relatively less affected by environment. They could serve successfully as genetic sources for breeding resistance to CEW. The rank correlation between the combined over year mean ranks and cultivar superiority performance measure value ranks was highly significant (r = 0.985). This suggests that either method of analysis could be suitable in identifying genotypes with stable resistance to CEW. The CEW larval bioassay technique was reliable in separating resistant and susceptible genotypes.