Preliminary Study Of The Onion Main Quality Traits, Genetic Effects

Six quality characters of twenty-three onion varieties were studied for comparison of different bulb color varieties and analysis of genetic correlation. The results showed the six quality characters of different varieties including same bulb color varieties and different bulb color varieties were different. White bulb varieties' s bulb tightness, dry weight, soluble solid content, soluble sugar content and pyruvic acid content were higher than those of other bulb color varieties. Red bulb varieties have the highest protein content of three bulb color varieties.The results from the analysis of genetic correlation showed that protein content was not significantly correlated with other characters. Soluble solid content was very significantly correlated with other characters except protein content. Bulb tightness was very significantly correlated with soluble sugar content and significantly correlated with soluble solid content and pyruvic acid content.A diallel cross among seven onion varieties using complete diallel design of Griffing' s method IV was made. The data of heterosis were observed in all crosses for six characters. The results indicated that most of the heterosis of bulb tightness, protein content and pyruvic acid content were negative. Soluble solid content and soluble sugar content showed positive heterosis generally. While dry weight content showed a very widely range of heterosis.The results from the variance analysis of combining ability showed that general combining ability (GCA) and special combining ability (SCA) were very significantly for six characters in model I and model II. Variety 2 and Variety 6 have better GCA in all characters, so they were very useful varieties for quality breeding. But it also showed SCA was not always accord with GCA.Genetic parameters of six characters were estimated. The results showed that the heredities of bulb tightness, soluble solid content, soluble sugar content and pyruvicacid content were conformed to additive-dominance model. And dominance action was more important than additive action, but the direction of dominance was decrease. The heredity of dry weight was primary controlled by dominance action and there also existed nonallelic interaction. The direction of dominance was enganced. The heredity of protein content was conformed to additive-dominance - nonallelic interaction model. And dominance action was more important than additive action, but the direction of dominance was decreased. The heredities of bulb tightness, soluble solid content, soluble sugar content and pyruvic acid content were controlled by oligogene. While the heredities of protein content was controlled by about two genomes. The narrow heritabilities of bulb tightness, protein content and pyruvic acid content were low, so they must be selected in late generation. The narrow heritabilities of dry weight content, soluble solid content, soluble sugar content was high comparatively, and they may be selected in early generation.