Genetic structuring of segregating populations of Psidium spp resistant to the southern root-knot nematode by Bayesian approach as basis for the guava breeding program.

There are no guava cultivars resistant to the Meloidogyne enterolobii; for this reason, genetic breeding has been performed by introgressing genes into the current cultivars through interspecific hybridization. We used 33 microsatellite markers for the genetic-molecular characterization of segregating populations of Psidium resistant to M. enterolobii, aiming at selection within and between populations for generation advancement in the guava breeding program. The average number of alleles per locus ranged from 1.60 to 2.09. Populations 1 (P. guineense × P. cattleyanum) and 5 (P. guajava × P. cattleyanum) obtained the greatest genetic diversity, which can be confirmed by the higher observed-heterozygosity values (0.422 and 0.312, respectively). Bayesian analysis showed that the populations were subdivided into three groups, agreeing with the number of groups observed by Nei's genetic distance. The population obtained from the P. guineense × P. cattleyanum cross differed from the others with a clear structuring, whereas the P. guajava × P. cattleyanum and P. cattleyanum × P. guineense populations were the most similar between each other. The SSR markers were efficient in discriminating the populations, and individual 80 may be employed in future crosses with guava, allowing generation advancement in the guava breeding program aimed at resistance to M. enterolobii.