RESISTÊNCIA POR ANTIBIOSE DE CULTIVARES DE TRIGO AO PULGÃO Rhopalosiphum padi L. (HEMIPTERA: APHIDIDAE)

Abstract

Wheat (Triticum aestivum L.) is the second most produced cereal in the world. Rhopalosiphum padi L. is one of the leading aphids affecting wheat fields worldwide. The mechanisms of resistance of wheat to R. padi are not well known. The identification of cultivars resistant to R. padi and the understanding of the mechanisms of molecular response involved in the infestation of wheat by this aphid, can contribute to the improvement for resistance to this pest. In this context, the present study aimed to evaluate the resistance of 15 commercial wheat cultivars to the aphid R. padi and also to determine the expression profile of genes already described as important in response to the aphid infestation in cereals in a resistant cultivar and one susceptible to R. padi. Antibiosis resistance analyzes of wheat cultivars were performed using bioassays with no chance of choice, in a controlled environment, infesting two aphids per plant and counting the total number of aphids 12 days after infestation. The expression of six aphid resistance genes in wheat was determined by RT-qPCR at 24 and 48 h after infestation. The main conclusions of this work were: (1) The cultivars showed significant differences for the levels of resistance, enabling the distribution of these cultivars in four groups: highly susceptible, susceptible, resistant and highly resistant; (2) The cultivars TBIO Audaz, ORS 1401, LG Oro, BRS Timbaúva, TBIO Sossego, ORS Vintecinco and BR 16 Rio Verde were classified as resistant, being indicated for use in genetic improvement; (3) The cultivar TBIO Sonic showed the highest resistance of the antibiosis type to R. padi, and the cultivar TBIO Consistency was highly susceptible; (4) The cultivars Embrapa 16 and BRS Timbaúva show differences in gene expression in 24 and 48 hours after being challenged by R. padi. The gene encoding lipoxygenase was repressed in the susceptible cultivar and maintained its basal expression in the resistant cultivar, 24 hours after infestation; (5) resistance-related protein expression was induced in the resistant cultivar, but not in the susceptible one, within 24 hours after infestation, and (6) the resistance presented by the cultivar BRS Timbaúva to R. padi is due to the ability of this genotype to prevent the immediate inhibition of the gene that encodes the lipoxygenase.