SSR identification of F2 progenies of E42-6 × Rizamat grape and their genetic tendency of berry shape

Abstract:【Objective】Table grapes occupy a major position in Chinese grape industry. The berry shape is one of the important traits for evaluation of the appearance quality of grapes. In order to explore the genetic variation tendency of grape berry shape, we used 528 F2 progenies generated from hybridizing E42-6 with Rizamat as experimental materials. Firstly we identified the authenticity of the F2 population through SSR fluorescent markers combined with capillary electrophoresis detection technology, and then we researched the genetic tendency and analyzed the inheritance of berry shape from F2 progenies, so as to provide a basis for the prediction of parental selection in grape fruit shape improvement breeding.【Methods】The crossing combination was made using E42-6 as female parent (round shape berry) and Rizamat (oblong shape berry) as male parent in 2012 and 528 F2 progenies were obtained. The hybrid plants bore berries in 2016. The leaves and berries were collected from grapevines grown in the vineyards of Research Institute of Grape and Melon of Xinjiang Uygur Autonomous Region in Shan-shan, Xinjiang province during August to October in 2019. The genomic DNA of each single plant of the hybrid combination was extracted and 40 pairs of SSR fluorescent markers combined with capillary electrophoresis-PCR method were used to identify the true hybrid offspring, the software GeneMapper v3.25 was used for data reading, the final analysis results were presented in the form of fragment size and exported in Excel. The berry shape indexes of F2 progenies such as berry width, berry length and fruit shape index were measured according to the conventional method The data were processed with Excel statistical software, and the genetic tendency of fruit shape was analyzed through coefficient variation (CV), transfer ability (Ta), heterosis rate.【Results】Based on the genomic DNA of the parents, 34 pairs of polymorphic SSR markers were screened out from 40 pairs of SSR markers to be used for further identification. Among them, 18 pairs of polymorphic markers amplified the specific complementary bands between the parents, and all of them confirmed that Xinya was the F1 progeny of E42-6 and Rizamat. After that, we randomly selected 5 pairs of SSR markers from 34 pairs of polymorphic markers to identify the F2 progenies. It was found that 520 progenies that contained the specific band from Xinya were screened as true selfing offsprings of Xinya, the true rate of F2 progenies was 98.5%. The fruit shapes of F2 progenies were widely separated, including round, oblong, oval, cylindric, obovoid, ovoid, oblate, heart-shape, curved-shape, and waist-shape although the fruit shape of the offspring was mainly oval and oblong, accounting for 64.6% . The berry width, berry length and fruit shape index were quantitative traits with continuous normal distribution. The coefficient variation of berry width was the smallest, which was 9.92%, while the ultra low dear of berry width was as high as 46.15%, it showed an obvious tendency toward low inheritance. The genetic transmitting ability of berry length was lower than 1. The average value of fruit shape index was slightly above the mid-parent value, there were some ultra high individuals, but more than half progenies had mid fruit shape index between parents’value, the genetic transmission ability of fruit shape index was 104.07%, showing a regression in the direction of increasing, indicating that additive effect occupied the dominant position and the fruit shape index could be stably inherited to the progenies.【Conclusion】It was feasible to use SSR fluorescent marker to identify the authenticity of F2 population generated from E42-6 and Rizamat. The rate of ture self-progenies was as high as 98.5%, and SSR markers could accurately and effectively identify the authenticity of F2 progenies in grape. In our study, the fruit shape of F2 progenies was mainly oval and oblong. The berry width, berry length and the fruit shape index were quantitative traits with continuous distribution. The ultra-low dear of berry width was high and showed an obvious degeneration genetic tendency. The average value of berry length was lower than the mid-parent value, presenting a negative degradation genetic trend. The average value of fruit shape index of F2 progenies was slightly higher than the mid-parent value, additive effect played a dominant effect in the inheritance of fruit shape index, this trait could be stably inherited to the progenies. There were some individuals of ultra high fruit shape index in F2 progenies. By selecting two parents with big difference in fruit shape, the probability of obtaining single offspring individual of ultra-high fruit shape index would be increased.