Estimation of Heterosis and General And Specific Combining Abilities in Some Sunflower (Helianthus Annuus L.) Hybrids

Abstract

Twenty-eight sunflower hybrids were produced, using two cytoplasmically male sterile lines as female parents and fourteen fertility restorer lines (testers). The hybrids and a commercial check (Hysun-33) were evaluated for two seasons (2000/01and 2001/02) at two locations; namely, the University of Khartoum Farm at Shambat and Rahad Research Station . The experiment was carried out under irrigation, using a randomized complete block design with three replications. Significant differences were detected among the tested hybrids for most of the studied characters, at the two locations and for the two seasons. Moreover, a wide range of variability among the fourteen testers and between the two lines was obtained for most of the characters. The genotype x location interaction was significant for number of seeds per head, 1000-seed weight and seed yield per head. In addition, significant location x season, genotype x season and genotype x location x season interactions were detected for all characters. Negative heterotic values, under the better- parent, were expressed by some of the hybrids produced from the female parents Kr and Ka for plant height, days to 50% flowering, days to maturity and percentage of empty seeds per head over the four environments. Positive heterosis over the better-parent was expressed by all the hybrids for stem diameter, head diameter, number of seeds per head, 1000- seed weight, seed yield per head and seed yield per hectare over the four environments. At Shambat, 14.3% and 78.6% of the hybrids obtained from the female parent Kr were high yielders than the commercial check in the first and the second seasons, respectively, wheras all the hybrids from the female Ka were high yielders than the check in the second season. At Rahad, 21.4% of Ka hybrids were high yielders than the check in the first season. All the characters studied were controlled by additive gene action over the four environments, except seed yield per head and seed yield per hectare at Shambat in the first season and head diameter and 1000-seed weight at Rahad in the first season, which were controlled by non-additive gene action. At Shambat, the best general combiner males for seed yield and seed components were SH-24 and SH-10 for number of seeds per head, SH-5 and SH- 24 for percentage of empty seeds, SH-6 and SH-2 for 1000-seed weight, SH-23 and SH-12 for seed yield per head and SH-23 and SH-2 for seed yield per hectare respectively, in the first and the second seasons. At Rahad, the best general combiner males were SH-12 and SH-8 for number of seeds per head , SH-3 and SH-21 for 1000-seed weight, SH-6 and SH-7 for seed yield per head and seed yield per hectare respectively, in the first and the second seasons. With regard to the females, Ka was the better general combiner for all the characters studied over the environments, except 1000-seed weight at Rahad in both seasons, where the female Kr was the better general combiner. The highest specific combining ability (SCA) estimates at Shambat were scored by the hybrids SHR-2 and SHR-13 for number of seeds per head, SHR-5 and SHR-13, for percentage of empty seeds, SHA-18 and SHA-24 for 1000-seed weight, SHA-6 and SHR-2 for seed yield per head and seed yield per hectare, respectively, in the first and the second seasons. At Rahad, the highest SCA estimates were obtained for SHR-2 and SHR-9 for number of seeds per head, SHA-18 and SHA-24 for 1000-seed weight and SHR-9 and SHA-6 for seed yield per head and seed yield per hectare in the first and the second seasons, respectively. The analysis of stability parameters indicated that the hybrids produced from the female parent Ka as well as the check were the highest yielders but sensitive to changing environments, hence they were adapted to favourable environments, on the other hand, those produced from the female parent Kr were resistant to changing environments, but they were average yielders, and thus they were adapted to poor environments.