How segregating populations of passion fruit react to CABMV infection?

Abstract

The passion fruit woodiness disease, caused by the cowpea aphid-borne mosaic virus (CABMV), is the most important disease and represents a limiting factor for culture. Cultivars with resistance levels are being developed from backcrosses associated with a recurrent selection program. Studies showing how segregating populations respond to infection over time and describing resistance are necessary and make it possible to characterize the genotypes and select the most promising ones. Therefore, the present study aimed to describe the pathogenesis; evaluate resistance in the Passiflora sp. × CABMV pathosystem; and select the most resistant individuals for generation advance in the recurrent selection program in passion fruit. Five generations of crossbreeding were used, namely, interspecific hybrid, backcrosses BC1.1 and BC1.2 and parents P. edulis and P. setacea. The plants were inoculated in a greenhouse and evaluated for resistance to CABMV. The area under the disease progress curve (AUDPC) was calculated and variance components and genetic values were estimated for the populations under study. High genetic variability was observed between the individuals, ranging from asymptomatic plants to plants exhibiting the most severe symptoms of the disease. Four phenotypic groups were formed, allowing greater differentiation between the generations and their parents. The presence of CABMV was confirmed in plants of the BC1.1 generation and of P. edulis, with characteristic symptoms of the virus. In asymptomatic plants, 75% of the individuals were considered resistant by PTA-ELISA and RT-PCR. The majority of individuals selected for resistance to CABMV belonged to the BC1.2 generation, which might thus be included in the recurrent selection program.