Dissimilarity based on morphological characterization and evaluation of pollen viability and in vitro germination in Passiflora hybrids and backcrosses

Abstract

Brazil is considered the main center of the genetic diversity and greatest worldwide producer of passion fruit. Passionfruit woodiness virus (Cowpea aphid born mosaic virus) is an important pathogenic agent of the passion fruit crop, causing severe losses in yield. Wild species of Passiflora are valuable sources of genetic resistance to this disease. Interspecific crosses are a promising method to incorporate resistance genes in commercial species (Passiflora edulis Sims.), despite problems with male sterility in developed hybrids. The objective of the present work was to study the dissimilarity based on morphological characteristics, and the viability and in vitro germination of pollen grains of progenitors, F1 hybrids, as well as progenies of the first generation of backcross BC1 [(P. edulis × P. cincinnata) × P. edulis]. Analysis of the severity of the viral disease showed that most genotypes were considered as susceptible to highly susceptible. The resistant hybrids did not show symptoms of foliar deformation. Cluster analysis showed two major groups; one represented by P. cincinnata and the second group by the hybrids and recurrent progenitor P. edulis. Morphological characterization of the hybrids showed phenotypic variation as to the color and shape of flowers, although the descriptors used were not able to show these differences. As expected, the progenitors (P. edulis and P. cincinnata) presented higher percentages of pollen viability, followed by the BC1-H45 progenies. The progenies of the BC1 will also be evaluated in the future with molecular markers aiming to accelerate the selection of hybrids with higher percentages of the genome of the recurrent parent.