Induction of resistance by silicon in wheat plants to alate and apterous morphs of Sitobion avenae (Hemiptera: Aphididae).

Despite the knowledge about the effects of silicon augmenting antibiosis and nonpreference of plants by apterous aphids, few studies exist on such effects with alate aphids. This study evaluated the effects of silicon fertilization on the biology of alate and apterous morphs of Sitobion avenae (F.) (Hemiptera: Aphididae), and the effect on nonpreference by S. avenae alates for wheat plants with or without silicon fertilization. A method for rearing aphids on detached leaves was evaluated comparing the biology of apterous aphids reared on wheat leaf sections and on whole plants with and without silicon fertilization. Because the use of detached leaves was a reliable method, the effect of silicon fertilization on the biology of apterous and alate S. avenae was assessed using wheat leaf sections. Biological data of aphids were used to calculate a fertility life table. Finally, the effect of silicon fertilization on the nonpreference of alate aphids was carried out for both vegetative and reproductive phases of wheat. Thirty alate aphids were released in the center of a cage, and the number of aphids per whole plant with or without silicon fertilization was observed. Silicon fertilization induced antibiosis resistance in wheat plants to apterous morphs as shown by reduced fecundity, reproductive period, longevity, intrinsic rate of increase, and net reproductive rate; however, alates were unaffected. Plants that received silicon fertilization had fewer alate aphids in both the vegetative and reproductive phases. Thus, silicon fertilization can reduce colonization by alates, enhancing nonpreference resistance, and population growth of apterous S. avenae in wheat plants.

Antibiosis and non-preference of Sitobion avenae (F.) (Hemiptera: Aphididae) on leaves and ears of commercial cultivars of wheat (Triticum aestivum).

Little is known on the resistance of wheat cultivars to Sitobion avenae (F.) in Brazil. The goal of this work was to assess the behavior and biology of S. avenae on four commercial wheat cultivars to verify the existence of resistance by antibiosis in leaves and ears and non-preference in the ears. The smallest net fecundity rates of S. avenae in wheat leaves have been found in the cultivars Embrapa 22 and BRS264, which did not differ between themselves. The intrinsic rate of increase of S. avenae was smaller in leaves of Embrapa 22 than in cultivars BRS254 and BRS Timbaúva. The smallest net fecundity rates of S. avenae in wheat ears were observed in the cultivars BRS254 and Embrapa 22. The intrinsic rate of increase of the aphid in the ear of cultivar Embrapa 22 was smaller than in BRS Timbaúva and BRS264, but did not differ from BRS254. The organ of the wheat plant in which the aphid was reared influences antibiosis resistance, but the cultivar BRS Timbaúva was considered susceptible and Embrapa 22 resistant to S. avenae in both plant organs tested. Ears of wheat cultivars tested did not show differences in the mechanism of resistance by non-preference to S. avenae.