Studies On Genetic Laws Of Some Quality Characters Of Pickling-type Cucumber(Cucumis Sativus L.)

The GCA(general combining ability) and SCA(special combining ability) of 5 main fruit quality characters(fruit length, fruit flesh thickness/fruit diameter-T/D, fruit fresh weight, total soluble protein content and sugar content) of 15 genotypes of pickling-type cucumber were analyzed with 5 varieties LN11,EP326,RiJieCheng,ZR22 and CiXi by Griffing II .The results showed that the GCA of 4 fruit quality characters of ZR22 (T/D, fruit fresh weight, total soluble protein content and sugar content) was higher and the GCA of fruit length was lower. Therefore, ZR22 was thought to be an ideal parent for quality breeding of pickling type cucumber. The SCA effects of 5 fruit quality characters were all positive in the combination LN11 ZR22, suggesting that it might have much potential in the way of heterosis breeding .The results of genetic correlation showed that the broad heritability of 5 fruit quality characters (total soluble protein content and sugar content, fruit fresh weight, fruit length/fruit diameter-L/D, fruit dry weight) were higher, but the narrow heritability of those characters lower, suggesting that selection in early generations for those characters was not easy to get better results but the heterosis of those characters could be used. The narrow heritability of fruit flesh thickness was higher, which could be selected and improved in early generation by individual selection. The relative genetic progress of fruit flesh thickness, fruit dry weight and fruit fresh weight was higher, which could be improved efficiently by fewer generation selections.The effect of direct selection was better than indirect selection for T/D. The effect of indirect selection for fruit dry weight, fruit fresh weigh through fruit length was better,the effects of indirect selection for total sugar content, fruit flesh thickness, fruit dry weigh, fruit fresh weigh through fruit diameter were superior too, but the total soluble protein content would be decreased .The effects of indirect selection for total soluble protein content and fruit dry weigh, fruit fresh weight through fruit flesh thickness and T/D were superior, but the total soluble sugar content would be decreased. The protein content had significantly negative correlation to the total soluble sugar content. So they must be as different breeding aims for making selection programs.The generation genetic effects for total soluble protein content and sugar content and T/D were analyzed with F1, F2, BC1, BC2, P1 and P2 generations of 3 relative characters by quantitative genetics. The results showed that the genetic ways of total soluble protein content and T/D accord with the additive-dominant model and the additive effect was superior, and the additive-dominant-epistatic model for the genetic way of total soluble sugar content with more obvious epistatic effect. The narrow heritability of total soluble protein content was lower, suggesting that higher selection for the character could be effective. However, the narrow heritability of T/D was higher, suggesting that earlier selection for that would be right.The relations between fruit crispness, fruit structure and cellulose content of pickling-type cucumber were studied preliminarily. The results showed that fruit crispness was influenced by several factors including fruit skin thickness, thin-wall cells increasing progressively, cellulous content and fruit hardness. The relationships among those factors showed that thicker epidermal cells might mean unsuitable fruit crispness. Fruit crispness would be better if the volume of thin-wall cells very close to epidermal size increased rapidly. No general and direct relations were found between fruit crispness and fruit cellulose content and the similar conclusion could be found in the relation between fruit crispness and fruit hardness.