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Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/17/1998 Publication Date: N/A Citation: N/A Interpretive Summary: The twospotted spider mite is a serious pest of soybean associated with periods of hot weather and dry conditions. Efforts to screen soybean germplasm for resistance to this arthropod pest have been limited because field screening is complicated by nonuniform and unreliable mite populations and an adequate laboratory bioassay is lacking for resistance screening and determining specific mechanisms of resistance. Selected soybean lines were evaluated in the laboratory in excised and intact (whole plant) leaf tests to determine the ability of these tests to detect differences in susceptibility or resistance to the twospotted spider mite. The excised leaf test, which was easier to set up and monitor and occupied three-fourths less growth chamber space, expressed less variation among variables measured and was more effective in detecting differences among soybean lines. This study demonstrated a reliable and uniform laboratory bioassay to screen large numbers of soybean lines for resistance to spider mites and for identifying specific mechanisms of resistance. Results of this study will aid soybean breeders and entomologists in the identification and development of soybean germplasm and cultivars resistant to the twospotted spider mite. Technical Abstract: Thirty-one soybean, Glycine max (L.) Merrill, accessions from maturity groups II through VIII were evaluated in excised and intact (whole plant) leaf tests to determine the ability of these tests to detect differences in susceptibility to the twospotted spider mite, Tetranychus urticae Koch. The excised leaf test which was easier to set up and monitor and took three-fourths less growth chamber space also had less variation among replications and repeated tests and was more effective in detecting differences among accessions. Although there were significant differences among soybean accessions within a maturity group for specific variables, results suggest that resistance to the twospotted spider mite is not present in the germplasm screened. Several accessions screened, with known resistance to foliar feeding insects, were less preferred for spider mite oviposition and development. However, it was apparent that the gene(s) controlling insect resistance do not impart the same level of resistance t the twospotted spider mite. Results of this study demonstrate that the excised leaf test presented is a reliable and uniform laboratory bioassay to screen large numbers of soybean germplasm for resistance to the twospotted spider mite. |
