Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 7/1/2009
Publication Date: 10/18/2009
Citation: Wilson, J.P., Ni, X., Rajewski, J.A., Dweikat, I., Buntin, G. 2009. Application of pathological principles to evaluating pearl millet for chinch bug resistance. Pg. 327-328 in Proc. 6th Asia-Pacific Congress of Entomology, Beijing, China, Oct. 18-22, 2009. Interpretive Summary: not required
Technical Abstract: Chinch bug [Blissus leucopterus leucopterus (Say) (Heteroptera: Blissidae)] is one of the most important insect pests on forage and grain pearl millet (Pennisetum glaucum L. R. Br.) in the southern US. Insect feeding damage is expressed as plant mortality, stunting, leaf sheath necrosis, and tiller mortality, reduced chlorophyll content and changes in photosynthetic rate. Pearl millet inbreds and hybrids were assessed for chinch bug resistance using these six parameters. Different experiments were conducted for forage or grain genotypes, and grain genotypes were evaluated under both subtropical and temperate climate conditions at Tifton, GA and Lincoln, NE, respectively. Resistance was consistently expressed as a slower rate of symptom development on resistant genotypes compared to susceptible genotypes. Inbreds with resistance superior to commercial standards were identified for hybrid development. Cluster analysis of the evaluation parameters allowed grouping genotypes into resistant, susceptible, and intermediate classes. Based on the A/Ci curves of selected genotypes, photosynthesis capacity of injured leaves were either suppressed or increased compared to the non-infested plants. In contrast, light response curves were suppressed in the chinch bug-injured plants compared to the non-infested plants, irrespective of their variations in insect injury ratings. These experiments revealed information on the genetic expression of resistance, which tended to be dominant or overdominant. Evidence for location-specific resistance caused by environmental conditions or genetic differences in the insect populations between locations was observed. Evaluations at multiple locations are needed to effectively identify resistance to damage caused by chinch bug feeding in pearl millet. Phytopathological techniques traditionally used to assess disease resistance and the adaptation of the techniques to these insect resistance assays will be discussed.