Combining ability of the stay green trait and seed moisture content in sunflower

Plants of sunflower (Helianthus annuus L.) which retain a green color in stems at physiological maturity are characterized as having the stay green trait. Research on inheritance of the stay green/early senescence trait may provide valuable information to plant breeders for developing new cultivars with better resistance to drought and pests, and increased standability. This study was conducted to determine the general (GCA) and specific (SCA) combining abilities of different female and male inbred lines in F1 hybrids for the stay green characteristic. The study included 36 sunflower hybrids produced by crossing six female lines to six male lines in a factorial mating design. Change in stem color was used as a criterion for the day green characteristic with stem color analyzed by a computer program called Maps and Image Processing System. The relative magnitude of ratios of the female and maize GCA components to the female and maize GCA plus SCA components for the day green trait, suggested that additive gene effects were more important than nonadditive gene effects in controlling stay Green expressed among hybrid combinations. However, significant SCA effects detected at physiological maturity also implied the contribution of nonadditive effects to the variation. Nonsignificant correlation coefficient between different color at physiological maturity and seed moisture content at harvest indicated that it is possible to develop hybrids with the stay green trait and low harvest seed moisture content. Significant but small correlation coefficients for stem color between different plant stages after anthesis suggested that selection would be most effective at physiological maturity