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RESISTANCE OF SORGHUM GENOTYPES TO THE APHID Rhopalosiphum maidis (FITCH, 1856) (Hemiptera: aphididae): II. NO CHOICE TEST

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Author(s): ALYSSON RODRIGO FONSECA | IVAN CRUZ | CÉSAR FREIRE CARVALHO | BRÍGIDA SOUZA

Journal: Revista Brasileira de Milho e Sorgo
ISSN 1676-689X

Volume: 4;
Issue: 3;
Start page: 323;
Date: 2005;
Original page

Keywords: Sorghum | corn leaf aphid | insect host plant resistance | antibiosis

ABSTRACT
The objective of this work was to evaluate the effect of sorghum genotypeson the biology of the aphid Rhopalosiphum maidis (Fitch). The experiments wereconducted at the National Corn and Sorghum Research Center of Embrapa, Sete Lagoas,MG, Brazil. Eight sorghum genotypes were tested, seven of them being of knownresistance to the greenbug Schizaphis graminum (Rondani) and the commercial cultivar BRS 303. A row of five linear meters of each material evaluated was planted weekly toprovide leaves for rearing aphids in laboratory. The experiments were conducted overtwo generations of the aphid. Nymphs about one hour old were individualized andmaintained on leaf sections from each of the eight cultivars. As second generation, itwas used newly-born nymphs obtained from parents reared in each genotype studied inthe previous generation. In both stages, the insects were kept in climatic chambers at 25± 1 ºC, RH 70 ± 10% and 12-hour photophase. The number of instars, pre-reproductive,reproductive and post-reproductive periods, total cycle, number of produced nymphs perfemale and insect weight at four and eight days old, using 15 replicates were evaluated.The experimental design was completely randomized in a factorial scheme (genotypes xgenerations x replicates). The genotypes TX 430 (IS x SC) and GR 1.1.1.1.1 reducedsurvival rate, reproductive capacity, reproductive and post-reproductive period and total cycle. Genotype BRS 303 was themost adequate host, providing a high nymph production, high survival rate and longerreproductive and post-reproductive periods and longer life cycle as well.
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