Mechanisms and bases of resistance in maize to southwestern corn borer and fall armyworm
1997
Williams, W.P. | Davis, F.M. (USDA-ARS, Mississippi State (USA))
Maize, Zea mays L., germplasm lines with resistance to leaf feeding by the southwestern corn borer (SWCB), Diatraea grandiosella Dyar, and fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), have been developed and released. A series of experiments were conducted to determine the mechanisms and bases of this resistance. Field experiments have shown that antibiosis is a mechanism of resistance to both insects. When resistant and susceptible maize genotypes were infested with either SWCB or FAW neonates, the larvae that were recovered 10 to 14 days later from susceptible genotypes weighed twice as much as those recovered from resistant genotypes. Laboratory experiments using excised leaf tissue and liquid pressed from leaves demonstrated that larval non-preference is also a mechanism of resistance of these germplasm lines. When experiments were conducted using callus tissue of susceptible and resistant maize genotypes, both SWCB and FAW larvae preferred to feed on callus of susceptible genotypes. Larvae that fed on the susceptible calli weighed twice as much as those that fed on resistant calli. Similar differences in size were observed when larvae were fed on Lyophilized leaf tissue of susceptible and resistant genotypes. Factors responsible for these differences in growth are not fully known; however, leaf tissue from the inner whorls of resistant genotypes tends to be tougher than that from susceptible genotypes. The cuticle and epidermal cell wall of resistant genotypes is generally thicker. Leaves of resistant plants have a higher fiber content and lower total protein content. A 33kD polypeptide found in callus tissue appears to be associated with resistant genotypes. Electrophoretic analysis of whorl leaf tissue also indicated a possible association of resistance to SWCB and FAW with 21kD and 36kD polypeptides.
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