HETEROSIS IN TOP-CROSS HYBRIDS OF DIVERSE CYTOSTERILE SOURCES OF SUNFLOWER (Helianthus annuus L.) / HETEROSIS EN LOS HIBRIDOS TOP-CROSS DEL GIRASOL CREADOS DE DIVERSAS FUENTES CITOESTERILES / HÉTEROSIS DANS LES HYBRIDES TOP-CROSS DE TOURNESOL (Helianthus annuus L.) OBTENUS DE DIVERSES SOURCES CYTOSTÉRILES

SUMMARY Standard heterosis was estimated for eight quantitative traits in top-cross hybrids of three diverse cytoplasmic male sterile (CMS) sources of sunflower viz., Helianthus petiolaris (CMS-PET1), Helianthus petiolaris ssp. fallax (CMS-PEF1) and Helianthus annuus ssp. lenticularis (CMS-ANL2) maintained under different nuclear backgrounds. The top-cross hybrids were derived by crossing the above three CMS sources with 12 male parents in a line x tester design. Significant heterosis over two standard checks in the desirable direction was observed for all traits. All three sources under study advanced the maturity in most of the hybrids. CMS-PET1 was found to be the best compared with the other sources as far as oil content was concerned. Mean performance of the hybrids for achene yield and other economically important characteristics indicated that the hybrids derived in the cytoplasmic background of CMSANL2 were the best followed by CMS-PET1 and CMS-PEF1 suggesting that CMS diversification in heterosis breeding programs would be rewarding in sunflower.