Self-incompatibility and phenotypic assessment of yield and quality in Passiflora alata, an understudied tropical fruit species

Despite their economic significance, some tropical fruit species are largely neglected, mainly in terms of genetics and breeding. This is particularly true for the sweet passion fruit (Passiflora alata), a crop gaining new popularity and market value due to its characteristic aroma and flavor. Importantly, P. alata is self-incompatible, and the fruit set is reduced (or does not occur) when genetically related individuals are crossed. Given this, we determined the compatibility relationships among eight full sibs, previously selected. Nearly 2,000 crosses were performed in a full diallel design, including reciprocal and self-pollination. We propose that the genotypes’ reaction is a consequence of a sporophytic mechanism involved in P. alata self-incompatibility. Significantly, the compatibility results were confirmed in another field experiment conducted in the same environment. This allowed us to choose the genotypes to be intercrossed, resulting in 24 families. Next, nine traits related to fruit quality and yield were assessed in a randomized block design with four replicates, and plots consisting of three plants. Using genotypic values predicted by BLUP and two selection indices, eight superior families (30%) were selected. At the same time, the flowering period of each family was assessed. The families show a coincident flowering peak in May, except for the one family and its reciprocal, both with a flowering peak in November. Our findings indicate that compatibility tests and flowering phenology should be considered in P. alata breeding programs to make fruits available to producers for as long as possible.