Mode of Gene Action for Resistance in Maize to Maize Streak Virus

Abstract

Maize streak virus (MSV) transmitted by Cicadulina leafhoppers causes severe yield loss of maize (Zea mays L.) in Africa. This paper summarizes our studies on gene action for resistance to MSV using generation mean analysis. Crosses were made between a resistant inbred (IB32) and four susceptible inbreds (BI4, B68, B73, and Moi7). A total of II 255 plants from the four sets of biparentul crosses, their F2, backcross, and F3 progenies were grown in four experiments under severe artifically induced MSV epiphytotics at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. Severity of streak symptoms on test plants was classified on a five‐point scale based on the amount of streaking of leaves. Under severe artificial infestation inside a screenhouse, average ratings of resistant and susceptible parents were 1.3 and 5.0, respectively. The average F1 rating was 3.13, which was close to the mean midparent value (3.15). The average F2 rating was 2.83, which was 0.3 units more resistant than the F1 value. The average rating of four F1 crosses in the field was 2.22, 0.81 units more resistant than the mean midparental value (3.03). Average rating of the F2 populations was 2.22, which was similar to that of the F1 (2.27). Backcross ratings were close to mean of the F1 and recurrent parent. Individual F3 plants derived from same rating of F2 plants showed considerable variation in ratings. Resistance to MSV from IB32 appeared to be inherited quantitatively with relatively small numbers of genes involved. The symptoms of MSV varied with the genetic background of the susceptible parent. Simple recurrent selection or modified backcross breeding methods could be used to breed for MSV resistance in Africa.