Genetic Diversity Analysis Of Wild Apple Resources In Ex-situ Conservation In Xinjiang

[Objective]Xinjiang wild apple(Malus.sieversii(Ldb.)Roem)is the dominant tree species in Tianshan wild fruit forest,which has important ecological and resource value.By studying the genetic diversity of wild apple resources stored in Luntai resource nursery,we hope to provide reference for the introduction of germplasm resources in the future,and provide basis for the rational utilization of germplasm resources and breeding of excellent varieties of wild apple in the south of Tianshan Mountains.[Method]Using 57 germplasm resources of ectopically preserved wild apple as materials,16 characters of flower,leaf and fruit were investigated,and the correlation,principal component and cluster analysis were carried out systematically.Then,the local resources of Xinjiang ’Xia Hong Rou’ and ’Kizialma’,the modern cultivation resource ’Royal Gala’ and the three high flavonoids and three low flavonoids from 57 wild apple resources in Xinjiang were used as materials to evaluate the fruit quality,nutrient content,color indexes and antioxidant capacity of the three types of apple resources,which provided certain data and theoretical basis for the protection and utilization of wild apple resources in Xinjiang and different breeding targets in the future.[Result](1)The nutritional quality of ectopic preserved Xinjiang wild apple fruits was analyzed,and the content of ’GB-3’ resource soluble solid was the highest,which was 20.14%.The titrable acid content of ’GB13’ is the highest 145.61 mg/g;The highest content of vitamin C in ’HDM-13’ was 27.31 mg/100g;The soluble sugar content of ’XY-5’ was the highest,which was 142.82 mg/kg.The total flavonoids content of’GB-1’ fruit peel was the highest,which was 2816.29 mg/kg.(2)The phenotypic diversity analysis was carried out on the Xinjiang wild apple.16 traits such as leaf,flower and fruit traits were selected for measurement and comparative analysis and the results of variance analysis showed that the coefficients of variation(CV)of the 16 phenotypic traits ranged from 15.63%to 60.32%,with an average of 31.84%,among which the average coefficient of variation of fruit quality traits was the highest,all above 50%.The above results showed that the diversity of phenotypic traits of ectopic preserved wild apple resources was very rich,and the diversity of fruit traits was even more abundant.(3)The correlation analysis of 16 numerical characters in germplasm resources of wild apple showed that single fruit weight had a significant positive correlation with fruit longitudinal diameter,transverse diameter and stem diameter.In addition,there was a significant negative correlation between total flavone content and single fruit weight.(4)When the cumulative contribution rate reached 80.785%,7 principal component factors were obtained by principal component analysis,and different biological information was revealed according to the characters with higher loading values.It was preliminarily suggested that leaf character indexes were to some extent the limiting factors of total flavonoids content in fruits.Therefore,attention should be paid to select the population with low principal component 1 when utilizing the total flavonoids content of wild apple germplasm resources.(5)After systematic clustering analysis,57 resources were divided into three categories at 9.0 Euclidean distance:The 17 resources in group Ⅰ were mainly intermediate transitional wild apple.Group Ⅱ consisted of 16 fruits,mainly containing high flavonoid content.Group Ⅲ consisted of 24 fruits,mainly of high quality and storable fruits.(6)Among the three kinds of apple resources the order of antioxidant capacity was wild resources>Xinjiang local resources>modern cultivated varieties,showing a transition trend from wild type to cultivated type.As intermediate improved varieties,the flavonoid content and fruit soluble solids of Xinjiang local varieties were higher than that of cultivated varieties.The color and fruit quality traits of Xinjiang wild apple resources were obviously inferior to those of local varieties and modern cultivated varieties,but the flavonoid substances and nutrients were much higher than those of local varieties and modern cultivated varieties,with stronger antioxidant capacity.Among them,’HDM-2’ has the highest total flavonoid content and antioxidant capacity,but its fruit character is poor,fruit size is small,pulp texture is hard,which is more suitable for the development and utilization of related health care products.