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Tropical Plant Pathology
Print version ISSN 1982-5676
VIVAS, Marcelo et al. Combining ability and heterosis for resistance to black-spot in papaya genotypes by diallel analysis. Trop. plant pathol. [online]. 2012, vol.37, n.5, pp. 326-332. ISSN 1982-5676. http://dx.doi.org/10.1590/S1982-56762012000500004.
Diallelic crosses were performed between eight papaya genotypes belonging to the 'Solo' and 'Formosa' heterotic groups (four belonging to each group). The 56 hybrid combinations (F1's and reciprocals) along with their parents were evaluated in a complete randomized block design for resistance to black spot disease, caused by Asperisporium caricae. The severity of black spot in leaves and fruits was quantified in two occasions, March and May 2010. When the genotype effect was significant, heterosis as well as general and specific combining ability were estimated from the severity data. The genotypes 'JS12-N', 'Sekati', 'Golden' and 'Sunrise Solo 72/12' displayed better general combining ability for both characteristics. Twelve hybrids displayed promising results for selection, with low values of specific combining ability for resistance to black spot leaves and fruits. The heterotic group did not affect hybrid performance or heterosis estimates. Heterosis in papaya for resistance to black spot may provide significant genetic gains from both inter-and intra-heterotic crosses, and especially from hybridizations involving genotypes of the 'Solo' group.
Keywords : Asperisporium caricae; Carica papaya; hybridization.