Genetic Diversity Analysis of Walnut Germplasm Resources Based on Bitter and Astringent of Fruits in Xinjiang

Objective:To explore the typical characters of walnut germplasm in Xinjiang. Methods:The introduction and localization of 38 varieties of walnut germplasm resources were the main objects. 7 appearance indicators and 7 bitter or astringent indicators (tannin, rutin, chlorogenic acid, quercetin, catechin, vanillic acid, gallic acid) were analyzed for variation, principal component analysis, and genetic diversity analysis. Results:The coefficient of variation of kernel weight was the largest and the coefficient of variation of fruit shape index was the smallest. The variation coefficient of rutin was 227.612%, the variation coefficients of catechins, chlorogenic acids and tannins were relatively small (13.563%, 34.635% and 35.810%, respectively), of which the tannin diversity index was the highest, so the tannin was the representative of bitter substances in the walnut fruit. The bitterness-related index diversity index ranged from 0.015~171.81, with the highest tannin diversity index. The cluster analysis divided 38 walnut germplasms into 4 categories. The first category covered 16 walnut germplasms. The main ones were California black walnuts and Zhongning walnuts, all of which were rootstock germplasms with low bitterness. The second type had 1 walnut germplasm, and California black walnut 1was a good rootstock;the third type had 20 walnut germplasms, mainly the main cultivated varieties in Aksu region, which had good appearance quality;the fourth type had only 1 Walnut germplasm that was a natural material for progeny and had the highest tannin acid content. Conclusion:Tannins were the main bitter and astringent substances in walnut fruit, other components may have more health effects;It was found that the south 6-4 seedling plant may have a good application potential for rootstock breeding. The study will lay a certain research thinking and methods for screening the low bitter and astringent germplasm and the good stock germplasm of the rich walnut resources in Xinjiang in the future, and further promote the improvement of the quality and efficiency of the Xinjiang fruit industry.