Development of screening technique and basis of resistance in black gram (Vigna mungo (L.) Hepper) against whitefly, Bemisia tabaci (Gennadius)
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Date
2011
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Punjab Agricultural University, Ludhiana
Abstract
The studies on development of screening technique and basis of resistance in black gram against whitefly, B. tabaci were conducted during kharif 2009 and 2010. The leaf injury symptoms due to whitefly were categorized into five grades (I-V). Experiments conducted on standardization of screening technique against B. tabaci confirmed that black gram genotypes can be effectively screened at 3rd trifoliate leaf stage using 100 whitefly adults per plant under screen-house. Evaluation of black gram genotypes against B. tabaci in multiple-choice test on the basis of whitefly resistance index (WRI) revealed that genotypes KU 99-20 and NDU 5-7 were moderately resistant (WRI=1.50) and also recorded significantly lowest whitefly population (eggs, nymphs and adults) as compared to other genotypes. The genotypes IPU 02-043, KU 7-602, KU 7-605, KU 7-618 and Mash 1-1 were categorized as susceptible (WRI ranging from of 2.59 to 3.05) and genotypes KU 7-504 and KU 7-505 as highly susceptible (WRI ranging from 3.66 to 3.70) to B. tabaci. The whitefly adult population among the three canopies (upper, middle and lower) showed non-significant differences. Leaf area, lamina thickness and trichome length were significantly and positively correlated with whitefly eggs, nymphs, adults and WRI, whereas trichome density and angle were negatively correlated. Total phenols, o-dihydroxy phenols, flavonols, peroxidase and catalase were found to be significantly but negatively correlated with whitefly nymphs, adults and WRI. The chlorophyll content indices declined significantly in all the genotypes under whitefly stress conditions, particularly in the lower canopy of the plants. Thus, black gram genotypes with narrow, thin and highly pubescent leaves having short, but erect trichomes and higher total phenol contents should be selected for developing black gram varieties resistant to whitefly.
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