Avaliação da resistência de genótipos crioulos de feijão-caupi Vigna unguiculata (L.) Walp. ao ataque de Callosobruchus maculatus (Fabr., 1775) (Coleoptera: Chrysomelidae: Bruchinae)

Abstract

Cowpea (Vigna unguiculata L.) has significant socioeconomic importance as a food supply and, in the Northeast of Brazil, contributes to the strengthening of family farming. One of its limitations is the attack of Callosobruchus maculatus (Coleoptera: Chrysomelidae) during the storage of the grains, which are managed by chemical control. However, given the search for sustainable methods, the use of cowpea creole genotypes deserves attention as an alternative, as they can provide resistance to this pest. Thus, the present study evaluated the effect of 13 cowpea genotypes (11 creoles and two commercial ones) on biological parameters of C. maculatus. In the first chapter, a general review on the topic studied was presented. In the second chapter, the susceptibility of the cowpea genotypes to the attack of C. maculatus was evaluated through tests with no choice. The experimental design was completely randomized, with 13 treatments and 10 repetitions. Biological parameters of the bruid were analyzed (number of eggs, daily, final and accumulated emergence, instantaneous rate of population growth, and loss of grain mass). Each treatment consisted of 30g of each genotype and 20 adult insects. After seven days the insects were removed and the number of eggs was counted, and after the emergence, the loss of mass of the grains was verified. Cluster analysis was performed to identify similarity between genotypes, resulting in three groups: group 1 (Bala, Canapú, Corujinha, Manteiguinha, Moita, Seridó and Semper Verde); group 2 (Azulão, Rib of Beef and Rabo de Tatu); and group 3 (BRS Pujante, Ligeiro and Tardão). To check if there was an association between the groups, principal component analysis was performed. In group 3, there were higher rates of oviposition, daily and total emergence, greater population growth, and greater prolongation of the immature phase of the pest. In group 2 there were intermediate values of biological parameters and in group 1 the lowest values of these parameters. It was concluded that group 3 genotypes are susceptible to attack by C. maculatus and those of group 1 resistant to antibiosis. In the third chapter, the attractiveness and preference for oviposition of insects in the evaluated cowpea genotypes were evaluated, through tests with a chance of choice. The same genotypes and conditions as the second chapter were used. Arenas were set up with three interconnected flasks. Insects were released in the central flask and cowpea genotypes in the side flasks (treatments and control). The Attractiveness Indices (AI), Preference for Oviposition (IPO) and the Emergency were analyzed. The design was completely randomized with 13 treatments, and five replications. The Moita genotype was more attractive; BRS Pujante, Ligeiro and Tardão repelled the pest, and the other genotypes were neutral. As for the IPO, the Costela de Vaca, Moita and Ligeiro genotypes were preferred for oviposition. Regarding the emergency, only the BRS Pujante genotype showed a difference, with less emergence than in the control. Thus, it was concluded that the genotypes Moita and Costela de Vaca are susceptible to pest, BRS Pujante is resistant to C. maculatus by antixenosis and antibiosis, and the other genotypes showed intermediate susceptibility.