Field screening maize germplasm for resistance and tolerance to western corn rootworms (Col.: Chrysomelidae)^†

Abstract

In the hopes of lessening the current reliance on soil insecticides, developing a viable alternative for transgenic maize hybrids, and providing sustainable options for Europe, researchers recently have been developing novel maize lines that exhibit resistance and/or tolerance to corn rootworm larvae. Here we report the results of a 2-year field experiment in a northern growing region assessing the resistance and tolerance of 10 experimental synthetic maize populations selected for varying levels of damage from western corn rootworm larvae, Diabrotica virgifera virgifera LeConte (Col.: Chrysomelidae) and four maize hybrids. Maize non-preference, antibiosis and tolerance to rootworms was evaluated using previously established methods, including: the Iowa 1-6 root damage rating scale, root fresh weight, compensatory root growth ratings and adult rootworm emergence. Among the experimental synthetic maize populations, BS29-11-01 was the most susceptible, and had a mean root damage rating that was greater than the highly susceptible maize hybrid B37 · H84. This line also had the lowest mean root fresh weight and one of the lowest mean compensatory root growth ratings. In contrast, CRW8-3 appeared to be tolerant to western corn rootworms, and had the lowest mean root damage rating, which was comparable with that of the non-transgenic hybrid DeKalb Ò 46-26.

Native Resistance to Western Corn Rootworm (Coleoptera: Chrysomelidae) Larval Feeding: Characterization and Mechanisms

“…An early step in designing an efÞcient breeding program for resistance is to identify sources of resistance (Pathak 1991). Considerable efforts have been devoted to identifying and developing maize germplasm with resistance to feeding damage by western corn rootworm larvae in the hopes of lessening reliance on insecticides and developing viable alternatives to transgenic hybrids (Branson et al 1983;Branson 1986;Hibbard et al 1999aMoeser and Hibbard 2005;Prischmann et al 2007;Tollefson 2007). Understanding of the defense mechanism(s) to western corn rootworm in maize is of importance in a breeding program.…”

Antixenosis in Maize Reduces Feeding by Western Corn Rootworm Larvae (Coleoptera: Chrysomelidae)

“…B37ϫH84 is a particularly susceptible maize genotype that has been used as a susceptible control in both Þeld and laboratory studies (Hibbard et al 1999bPrischmann et al 2007Prischmann et al , 2009aEl Khishen et al 2009). In the current study fewer larvae fed and stayed on this line than on most of the other genotypes ( Fig.…”

“…Alternatives also are desired in Europe, where western corn rootworm has recently become a problem (Kiss et al 2005) but where transgenic maize for rootworm management may not be cultivated. Maize genotypes that exhibit resistance to western corn rootworm larval feeding may pose a viable alternative to insecticides and transgenic maize (Branson et al 1983;Hibbard et al 1999b;Prischmann et al 2007Prischmann et al , 2009bTollefson 2007). In Þeld tests, seven sources of native resistance in maize generally had less feeding damage, fewer and smaller larvae and fewer adults recovered than the susceptible maize controls ).…”

The Present and Future Role of Insect-Resistant Genetically Modified Maize in IPM

“…Epidermal leaf toughness also can be used to identify resistant varieties effective across a wide range of lepidopterans, including tropical pests of maize (Bergvinson et al, 1994). Most research related to maize resistance to D. v. virgifera, has focused on tolerance, as plants with large root systems or high compensatory root growth are more tolerant to D. v. virgifera feeding (Prischmann et al, 2007).…”