Inheritance trend of fruit traits in F1 progenies of ‘Vidal’ and ‘Chardonnay’ of grape

Abstract:【Objective】Hybrid breeding is a time consuming work, and the key to the success of the hy- brid breeding is to select parents reasonably. This work aimed at studying the inheritance trend of the fruit traits of the hybrid progeny of wine grape in order to provides a theoretical basis for the scientific selection of parents in wine grape hybrid breeding, and improve the breeding efficiency of wine grape.【Methods】The fruit quality indexes such as average panicle weight, average berry weight, fruit shape index, skin to flesh ratio, soluble solids, titrable acid content, juice yield and pH value were determined  by the conventional method with 105 hybrid individuals derived from the crosssing between‘Vidal’and‘Chardonnay’. 100 g of fresh fruits of each sample was quickly frozen with liquid nitrogen and then was stored in an ultra-low temperature refrigerator, and the content of phenolic compounds such as total phenolics content, tannin content, total flavonoids content, and flavanols content in fruit skin, flesh, and seeds were uniformly determined by colorimetry. The data were processed with Excel statisti- cal software, and the genetic variation of fruit traits was analyzed using coefficient variation (CV), trans- fer ability (Ta), heterosis rate, and the normal distribution map was used to reflect the genetic tendency of the progeny.【Results】The combinative Ta of the average panicle weight and other seven indexes of the fruits of the 105 individuals ranged from 60.72% to 112.07%. The separation of quality traits was high, and the genetic tendency was normally distributed. The CV of the average panicle weight was 48.85%, and showed a high ultra low parental inheritance; the CVs of fruit shape index and pH were 6.73% and 9.38%. The rate of transgresive segregation over the higher parent of the titratable acid of the F1 progeny was 33.33%, showing strong exceeding ability over the parent. The content of soluble solids and skin to flesh ratio were widely separated. The content of soluble solids was 15.02% to 25.65%, and skin to flesh ratio was between 0.20 to 0.40. The higher fruit shape index was concentrated on 0.96 to 1.10, and the separation was smaller. The average panicle weight and average berry weight showed a regression in the direction of decreasing, and pH showed a regression in the direction of in- creasing. The phenols in different parts of the fruits showed continuous variation and the genetic tenden- cy was normal distribution, and the CV was high. The CV of the total phenols in the skin was the high- est, but the rate of transgresive segregation over the higher parent of the total phenols in the flesh was 0, and the total phenols content in the flesh were 0.79 mg·g-1 to 1.21 mg·g-1, and the rate of transgresive segregation below the lower parent was 79.05%. The total phenolic content in the seeds maintained a high Ta, and the hybrid individuals were widely separated and present a continuous distribution; the con- tent of tannin in the skin was concentrated on 6.80 mg·g-1 to 12.89 mg·g-1, which was lower than that of maternal Vidal, and the rate of transgresive segregation below the lower parent was 45.71%. The genetic reduction effect of the progeny was obvious; the heterosis rate of tannin content and flavanol content in the flesh were positive. The content of flavanol in the seeds was higher than that of parents, and the content of flavanol in the seeds was 10.73 mg · g-1, which was 37.21% and 83.11% higher than that of parents‘Vidal’and‘Chardonnay’respectively. There were 79.48% of the individuals of the progeny with the total flavonoid content in the skin lower than that of the male parent‘Chardonnay’, and the to- tal flavonoid content in the flesh was distributed in a small direction, and concentrated on 0.10 mg · g- 1to 0.14 mg·g-1, showing less inheritance than that of the parents. The rate of transgresive segregation below the lower parent of the total flavonoid content in the seeds was 84.76%.【Conclusion】The contents of the acid and sugar in the progeny were widely separated and tended to be similar to the parent with high acid and low sugar. The color of the skin of the hybrid grapes depended on the color of the parents, and the fruit skins of 105 individuals was all green. The inheritance trends of the phenols in the differ- ent parts of the fruit of the progeny were different. The total phenol content in the fresh, the tannin con- tent in the skin, the total flavonoids content in the fresh and seeds were inherited in a smaller direction, and indicating a genetic degeneration effect. But the content of total phenols in the skin, the tannins and flavanols in the fresh had a transgresive segregation over the higher parent It could be used as the theo- retical basis for selecting parents in hybrid breeding.