Leveduras e seleção de genótipos como estratégias para o manejo da palma forrageira

Abstract

Native to Mexico, prickly pear cactus is a crop well adapted to the adverse conditions of the semiarid. This cactus is intensely cultivated in the dry regions, high rusticity and high conversion of water. Cultivated in areas with a high level of poverty in the states of Northeast Brazil, prickly pear cactus has great socioeconomic importance for this region, where there are long periods of drought, serving mainly animal feed in small properties. The diseases of the prickly pear cactus have been little studied in Brazil and almost all the studies only describe the symptomatology and the patogenicity of the causative agents. Among them, fusariosis caused by the fungi Fusarium oxysporum and Fusarium equiseti, affect the cladodes-seeds and cladodes of the base in adult plants, where they wither and fall on the plant a few days after the infection. The infected cladodium tissues become aqueous, darken and expose the internal woody structures. The roots rot, exhibiting reddish-brown coloration. The objectives of this work were to evaluate the potential of yeasts in the control of the control of fusariosis in prickly pear cactus, with the use of biocontrol through yeasts and genetic control through resistant varieties. Biocontrol tests were carried out in cladodes and in vitro with the yeasts Cystobasidium slooffiae, Candida carpophila, Rhodotorula mucilaginosa, Aureobasidium pullulans, Cyrenella elegans and Debaryomyces hansenii, all of which presented promising results as sources of bioactive compounds with antifungal action. Of these, yeast C. carpophila stands out, its chloroform extract showed high efficiency compared to the fungicide Tecto SC® in the control of F. oxysporum and F. equiseti. In the trials with genotype selection, six genotypes were the most promising for fusariosis resistance and could be used by breeders in future crosses to obtain fusariosis resistant prickly pear cactus. With this work we propose viable alternatives for the management of the fusariose of prickly pear cactus.