Resistance to Mexican Bean Beetle and Corn Earworm in Soybean Genotypes Derived from PI 2276871

Abstract

Progeny of three advanced soybean [Glycine max (L.) Merr.] backcross populations {‘Forrest’ ✕ [‘Bragg’ (2) PI 227687]). {Bragg ✕ [Bragg (3) ✕ PI 227687]} and {Bragg X [Bragg (3) ✕ PI 227687]) were sc reened for resistance to Mexican bean beetle (MBB) (Epilachna vorivestis Mulsant) and corn earworm (CEW) [Heliothis zea (Boddie)] defoliation in 1977 and 1978. Of the 258 progeny evaluated, 53% were similar to the resistant check PI 227687 in MBB resistance, but only 7% exhibited dual resistance to MBB and CEW. The level of MBB resistance differed significantly (P ≤ 0.05) among the 17 CEW‐resistant progenies from the three populations. Visual estimates of CEW feeding preference accurately indicated resistance in 73% of all observations, as compared to resistance ratings based on weight of leaf tissue consumed.Results of the study indicated that levels of MBB and CEW resistance equal to or greater than that of PI 227687 exist in progeny from the three backcross populations tested, and that evaluation of CEW leaf feeding resistance by visual estimate appears to be a useful method of rapidly eliminating large amounts of susceptible germplasm. The low incidence of progeny with CEW resistance among those with high MBB resistance suggested that indirect selection for resistance to CEW leaf feeding by screening for MBB resistance may be ineffective, and that future breeding efforts should utilize direct selection for resistance to CEW defoliation.