Potential of dioecious progenies of papaya plants for resistance to powdery mildew

ABSTRACT Landraces are important sources of genetic variability to be exploited by plant breeding programs. In Brazil, papaya is commercially grown mainly in the states of Espirito Santo and Bahia but, domestically, it is grown throughout the extensive Brazilian territory. However, exploration studies of genetic variability in local varieties of papaya are incipient in the country. The aim of this study was to evaluate the potential of 20 dioecious papaya genotypes for traits related to resistance to powdery mildew (Streptopodium caricae). Thus, this experiment was conducted in a greenhouse, in randomized block design, with four replicates and one plant per plot. The following were evaluated: incidence of leaves with powdery mildew symptoms and severity of powdery mildew in the fifth and seventh leaves. The obtained data were subjected to analysis of variance and mean comparison test via the least squares method. The variance components and the genetic value of progenies for incidence and severity of powdery mildew were also estimated via mixed models. There was a favorable situation for selection aimed at resistance to powdery mildew, with heritability ranging from 51.57 to 67.82 and selective accuracy above 70%. PMI1, PMI6, PMI8, PMI11, PMI12 and PMI15 stood out for presenting potential to reduce both the incidence and the severity of powdery mildew on foliage.