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Induced resistance to bean leaf beetle in soybean

Srinivas Parimi, University of Nebraska - Lincoln

Abstract

Greenhouse studies were conducted to investigate and demonstrate the phenomenon of induced resistance to bean leaf beetle in soybean. Different elicitors such as, mechanical injury, chemical inducer (BTH) and herbivory by the bean leaf beetle, Cerotoma trifurcata (Forster), and soybean looper, Pseudoplusia includens (Walker), were studied. A pairwise comparison of leaflets from treated plants with untreated (control) plants revealed that soybean looper herbivory was a better inducer than the other treatments. However, herbivory by bean leaf beetle and BTH applied following artificial defoliation also induced resistance against bean leaf beetle feeding. Studies conducted with two cultivars (Colfax and Williams 82) and a soybean germplasm line (HC 95-24MB) using the same treatments demonstrated that soybean looper herbivory was again a better inducer than other treatments in the soybean entries tested. Herbivory by bean leaf beetle, BTH, and BTH followed by artificial defoliation, were also found to induce resistance against bean leaf beetle. ^ Cross resistance studies demonstrated that soybean looper herbivory offered better cross resistance after induction to subsequent feeding by bean leaf beetle. However, herbivory by bean leaf beetle also induced resistance against the soybean looper. Studies conducted to demonstrate the longevity of the induced response revealed that induced response was highest on 14th day after treatment (DAT) and response was lowest on 25th DAT. The levels of induced response varied on other sampling days and induced responses were statistically different among highly significant sampling days. ^ In another study, the effect of different concentrations of BTH was studied for feeding preference of bean leaf beetle. BTH at 25 ppm concentration was found to show lower preference index (PI) when the plants were treated at unifoliate leaf stage. Preference index was calculated based on the acceptability of leaflets from untreated and treated leaflets. At V6 stage, feeding preferences, from leaves treated with 25ppm and 40 ppm concentrations of BTH showed lower PIs when compared to other concentrations. But in both the soybean growth stages, artificial defoliation followed by BTH spray at 25 ppm concentration showed response at comparable levels with BTH at 25ppm alone. ^

Subject Area

Agriculture, Agronomy|Biology, Entomology|Agriculture, General

Recommended Citation

Parimi, Srinivas, "Induced resistance to bean leaf beetle in soybean" (2000). ETD collection for University of Nebraska - Lincoln. AAI9958397.
http://digitalcommons.unl.edu/dissertations/AAI9958397

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