Biologia e comportamento de Sitobion avenae (Hemiptera: Aphididae) em quatro cultivares comerciais de trigo (Triticum aestivum L.)

Abstract

The use of resistant wheat cultivars to S. avenae is important for the management of culture due to the potential damage of aphid. In Brazil, however, little is known about the resistance of wheat cultivars to S. avenae. The goal of this work was to assess the behaviour and biology of S. avenae in leaves and ears of four commercial wheat cultivars to verify the existence of resistance by antibiosis into leaves and ears and no preference in the ears. For the evaluation of the biology of S. avenae were used four wheat cultivars: BRS254, BRS264, Embrapa 22 and BRS Timbaúva. The period of development of S. avenae in wheat leaves was lower in the cultivar BRS264 (8.78 ± 0.44 days) than BRS254 (10.33 ± 0.3 days). The smallest net reproduction rates of S. avenae in wheat leaves have been found in the cultivars Embrapa 22 (Ro = 1.7 ± 1.42) and BRS264 (Ro = 2.8 ± 0.64), which don t differed among themselves. It was verified that the finite rate of increase and intrinsic rate of increase of S. avenae were smaller in leaves of the cultivar Embrapa 22 (λ = 1.04 ± 0.015; rm = 0.04 ± 0.015) than in cultivars BRS254 and BRS Timbaúva. The average development period of S. avenae in wheat ears ranged from 8.9 to 9.3 days and not presented significant differences between cultivars evaluated. The reproductive period and the longevity of the aphid were higher in the ears of the cultivar BRS Timbaúva (5.4 ± 7.6 ± 0.33 and 0.34 days) than BRS254 (3.5 ± 4.8 ± 0.42 and 0.55 days). The total reproduction of S. avenae in wheat ears was greater in BRS Timbaúva (22.4 ± 1.72 nymphs) than BRS254 (12.4 ± 1.90 nymphs) and BRS264 (13.5 ± 0.98 nymphs). The smallest net reproduction rates of S. avenae in wheat ears were observed in the cultivars BRS254 (Ro = 7.9 ± 0.84) and Embrapa 22 (Ro = 8.2 ± 0.90). The intrinsic rate of increase of the aphid in the ear of cultivar Embrapa 22 (rm = 0.16) was smaller than in BRS Timbaúva and BRS264, but didn't differ from BRS254 (rm = 0.18 ± 0.010). There was variation in antibiosis resistance of wheat cultivars to S. avenae according of the tissue and/or phenological stage plants in the aphid develops. The cultivar BRS Timbaúva was susceptible and Embrapa 22 was resistant to S. avenae in the leaves of the vegetative stage and in the ears. The BRS 254 was resistant to aphid when evaluated their ears and susceptible when evaluated the leaves. The opposite was observed to BRS 264, which was resistant in the leaves and susceptible when was evaluated the ears. Ears of wheat cultivars tested did not show differences in the mechanism of resistance by non-preference to aphid S. avenae.