Estimation of Genetic Parameters for Yield, Yield Components and Some Phonological Characters in Sunflower Through Line X Tester Analysis

Abstract

The development of the F1 hybrids in major food crops and methods of hybrid seed production are imperative for achieving the important breeding goals. Thus evolving high yielding and better quality varieties play a decisive role in crop improvement programmes. Sunflower is also a crop in which genetic variance could be exploited considerably for higher seed and oil yields in the form of F1 hybrids. The best F1 hybrids, however can obtained by crossing of parents with good general and specific combiners and having high proportions of additive, dominance or complementary epistatic genes for the favourable expression of the seed yield, yield components and oil yields. Major improvement in sunflower breeding requires the urgency in evolving the heterotic hybrids which can best be achieved by tapping combining ability and heterotic vigour of F1 hybrids developed from crossing of genetically diverse female lines with male restorers. The sunflower hybrids are considered more stable, uniform in plant stand, highly self-fertile, highly productive in terms of seed yield and oil content, earlier in maturity, resistant to lodging and diseases. The present studies were carried-out at experimental field of Oil Seeds Section Agriculture Research Institute, Tandojam from 2008 to 2010. Six lines T-4-0319, PAC-0505, HO-I, Hysun-33, Peshawar-93 and CMS03 and three testers PAC-0306, PAC-64-A-93 and SF-187 were crossed in a line x tester mating design, thus 18 cross combinations were developed for evaluation and genetic analysis of seed germination percentage, days to initial flowering, days to 75% flowering, days to maturity, number of leaves plant-1, plant height, head diameter, number of seeds plant-1, 1000-achene weight, seed yield plant-1, seed yield kg ha-1, oil content and oil yield kg ha-1. The analysis of variance revealed significant differences among the parents, crosses and parents vs. crosses for phenological, seed yield and oil traits in F1 and F2 hybrids. The significance of mean squares of parents vs. crosses observed for all the studied traits demonstrated the scope of heterosis breeding in sunflower hybrids while the significant differences between lines x tester interactions indicated the importance of specific combining ability (SCA) of the hybrids which demonstrated the importance dominance or non-additive variances and genes involved in the expression of studied traits. The significant mean squares due to lines and testers both determine the general combining ability (GCA) revealed the prevalence of additive variances for the studied traits. Significant genetic variability among the plant traits is particularly useful because variations in these traits would allow further improvement in sunflower yield and quality traits. The major role of dominant genes was very obvious because the ratio of σ2 SCA/ σ2 GCA was higher and degree of dominance (σ2D/ σ2A) being greater than unity. These results indicated the preponderance of dominant gene action suggesting the feasibility of xi hybrid crop development. General combining ability estimates revealed that CMS lines HO-I, T-4-0319 and PAC-0505 whereas tester parents PAC-0306 and PAC-64-A-93 were found as the best general combiners for early maturity, yield and oil traits, hence these parents may be preferred for hybridization programmes so as to develop hybrids and synthetics varieties. Specific combining ability and heterotic effects are very important estimates for determining the suitability of F1 hybrid crop development. The hybrids T-4-0319 x SF-187, HO-I x PAC-arg-0306, Peshawar-93 x SF-187 manifested higher positive SCA and heterotic effects for seed and oil yields while gave negative but desirable SCA effects for phenological traits and plant height. The hybrids which manifested best specific combining ability is attributable to dominant or over-dominant type of genes, hence are desirable for the exploitation of hybrid crop development or selection of transgressive segregants in later generations of selection. The heritability estimates are generally low to moderate which is due to greater portion of dominant variances and dominant genes against the additive variances. These results suggested that selection for such traits may be exercised in later filial generations while giving the opportunity of recombination to occur between desirable genes. Generally, correlation results suggested that leaves plant-1, head diameter and 1000-achene weight have shown strong associations with seed and oil yields, hence leaves plant-1, head diameter and 1000-achene weight may be used as the most reliable selection criteria to improve oil content and seed yield in sunflower breeding programmes.