Resistance to Cowpea aphid-borne mosaic virus in species and hybrids of Passiflora: advances for the control of the passion fruit woodiness disease in Brazil

The potyvirus-induced passion fruit woodiness disease (PWD) is considered the most important limiting factor for passion fruit production in several countries. In Brazil, PWD is caused by the Cowpea aphid-borne mosaic virus (CABMV), and to date there are no reports on the existence of P. edulis genotypes resistant to this virus. Thus, resistance gene introgression from wild Passiflora species for a commercial species, via interspecific hybridization, is one of the strategies adopted in order to control the disease. The current study's goals were to: confirm CABMV occurrence under field conditions; assess the resistance to CABMV in 178 Passiflora genotypes constituted by interspecific hybrids and their parents (P. edulis and P. setacea), as well as to estimate genetic parameters for the area under the disease progress curve (AUDPC), in order to obtain cultivars of sour passion fruit resistant to CABMV in future. The experimental design was set according to unbalanced randomized blocks with two repetitions. Data referring to the AUDPC were analyzed by means of the mixed models methodology (REMI/BLUP). CABMV infections were confirmed in sour passion fruit plants and in interspecific hybrids by observing foliar mosaic symptoms and by PTA-ELISA with specific antiserum against CABMV. There was a difference on the intensity of symptoms induced by CABMV for the 178 Passiflora genotypes assessed under natural occurrence conditions. The higher AUDPC values were obtained for 41 hybrids and for all P. edulis genotypes. In turn, lower values were estimated for 115 hybrid genotypes and for all P. setacea individuals. Of the 31 genotypes assessed by PTA-ELISA, 28 were considered resistant, out of those three P. setacea genotypes and 25 hybrids. Estimated AUDPC heritability values (0.99) and accuracy (0.99) enable inferring that resistance to CABMV within the assessed population was highly inheritable, allowing high selective efficiency. Resistant hybrid plants will be able to be selected and recombined with P. edulis genotypes and, again, assessed in order to corroborate the resistance to the virus, providing means of following up with the breeding genetic program on CABMV resistance.