Submitted to: International Plant Resistance to Insects Workshop Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 15, 2008
Publication Date: February 10, 2008
Citation: Ni, X., Wilson, J.P., Buntin, D. 2008. Impact of chinch bug feeding on photosynthesis of forage pearl millet. International Plant Resistance to Insects Workshop, February 10-13, 2008, Ft. Collins, Colorado. p. 50. Interpretive Summary: not required
Technical Abstract: Chinch bug [Blissus leucopterus leucopterus (Say)] (Heteroptera: Blissidae) is one of the most important insect pests on pearl millet (Pennisetum glaucum L. R. Br.) production in the Coastal Plain region. Twenty-nine forage pearl millet germplasm entries were assessed for chinch bug resistance using modified chlorosis and stunting ratings. The chlorosis rating scale (1-4) was: 1 = all plants were normal and green; 2 = less than 25% of the plants showing leaf discoloration; 3 = 26 - 50% of the plants showing leaf discoloration; and 4 = over 50% of the plants showing leaf discoloration. The stunting rating scale (1-4) was: 1 = all plants had normal height; 2 = less than 50% of the plants were stunted; 3 = more than 50% of the plants but not all plants were stunted; and 4 = all plants were stunted. Leaf chlorosis ratings differed among the 29 entries (F = 4.75, df = 28, 85; P = 0.0001), but the stunting ratings did not (F = 1.42, df = 28, 85; P = 0.1125). While chlorophyll content (SPAD meter measurements) on flag leaves was not significantly different among the entries (F = 1.27, df = 28, 85; P = 0.2039), photosynthetic rate differed (F = 1.9, df = 28, 85; P = 0.0129) among the 29 entries. To differentiate the impact of chinch bug feeding on light and dark reactions of plant photosynthesis, light and CO2 (or A/Ci) response curves of the symptomatic and asymptomatic plants within the most resistant (entry 1245) and susceptible (entry 1223) germplasm entries were compared. In the most resistant germplasm (entry 1245), chinch bug-injured (symptomatic) plants showed a suppressed light response curve, but CO2 response curve was not affected when compared with the asymptomatic plants. In contrast, in the most susceptible entry (entry 1223), both light and CO2 response curves were suppressed in the symptomatic plants when compared with the asymptomatic plants. The experiment results indicated that the least amount of chinch bug injury in the resistant pearl millet germplasm might be related to the minimal impact of chinch bug feeding on CO2 assimilation capacity (or CO2 response curves).