Response of two maize synthetics to recurrent selection for resistance to first-generation European corn borer (Lepidoptera: Pyralidae) and Diplodia stalk rot

Four cycles of recurrent selection in two maize, Zea mays L., synthetics, BSAA and BSBB, were done to select for resistance to first-generation European corn borer (ECB), Ostrinia nubilalis Huebner, and Diplodia (Diplodia maydis (Berkeley) Saccardo) stalk rot (DSR). Recurrent selection was based on the evaluation of S sub(1) lines. Two cycles of recurrent selection in BSAA and three cycles in BSBB produced populations that were as resistant to leaf feeding by the ECB as the highly resistant single-cross check, B75 x CI31A, after which no further progress was made. The level of resistance to ECB and DSR in the population crosses and test crosses suggests that the genes governing resistance to these two traits are acting in an additive manner. The results indicate that improved standability in environments conducive to stalk rot development may require selection for physical stalk strength as well as for resistance to stalk-rotting organisms.