Genetic variability and stability analysis in sunflower(Helianthus annuus,L.)
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Information on genetic variability and stability of yield and yield components of sunflower in Zambia is lacking. The study was undertaken to determine the magnitude of yield; determine the relationships between yield and it's components; and estimate the heritability and stability of important traits in sunflower. Twenty five genotypes representing a random sample of the breeding populations in an on going sunflower improvement programme were grown in a 5 X 5 triple lattice design in 5 locations in the 1993/94 growing season. Data on kernel yield, kernel yield/head, oil content, oil yield, head diameter, stem diameter, plant population, plant height, average number of leaves/plant, number of days to 50% flowering, 1000 kernel weight and kernel % were collected and/or derived. The magnitude of yield was determined at harvesting. The relationship between yield and it's components was determined by path coefficient analysis. Presence of genetic variability was indicated by significant genetic variance. Heritability was estimated from variance components. Stability analysis was also done. The magnitude of kernel yield was found to be comparable with world averages though the average kernel yield of 1163 Kg/ha was below the country range of 1500 to 2000 Kg/ha) due to poor rains. High correlations between kernel yield and plant height (r = 0.420**), stem diameter (r = 0.589**) and kernel yield/head (r = 0.658**) were observed but their direct effects on kernel yield were very small (-0.216, -0.154 and -0.189 respectively). However, their indirect effects were more positive mostly through head diameter (0.127, 0.174 and 0.141 respectively). Head diameter showed large direct effects on both kernel yield (0.311) and oil content (0.581). The direct effect of 1000 kernel weight on oil yield (0.173) was large relative to overall correlation (r = 0.195**). The genetic variances for kernel yield, oil content, oil yield, head diameter, plant height, kernel yield/head and 1000 kernel weight were significant (P < 0.05). The broad sense heritability estimates for kernel yield ranged from 5.42% in Golden Valley to 33.01% in Monze; overall the estimate was 7.12%. For oil content the estimates ranged from 14.95%) in Mt Makulu to 52.35% in Monze with an overall estimate of 11.43%i. Similarly those of oil yield, plant height, stem diameter and 1000 kernel weight ranged from 8.36% in Golden Valley, 9.36% in Monze, 5.77% in Mt Makulu and 5.54% in Mt Makulu respectively to 26.78%) in Monze, 61.96%) in MRS, 27.27%o in Mt Makulu and 37.66%) in Monze respectively with the overall estimate being 20.37%, 10.20%), 0.23%), and 2.51% respectively. For head diameter the estimate was 17.33%) in Mt Makulu and 2.97% overall. Genotype X location interaction effects were significant for kernel yield, oil yield, 1000 kernel weight, stem diameter and plant height. Sunflower with respect to kernel and oil yield showed average ability to be consistent across locations. Overall the magnitude of yield was found to fall within an acceptable range with genetic variability being evident in the population. Head diameter alone could be a usefiil selection criterion for kernel yield and oil content; 1000 kernel weight for oil yield. Plant height and stem diameter together with head diameter could be useful indicators for early identification of elite lines with respect to kernel yield and oil content. Genetic variability for all traits studied was evident and the population was found to have average ability to perform consistently across environments.