Characteristics of fruit mineral nutrition of 21 Carya cathayensis clones in Zhejiang province

Abstract: 【Objective】Carya cathayensis is an important ecological and economic dry fruit tree species in China. Studying and comparing the differences in mineral element contents in the fruit of 21 Carya cathayensis clones in Zhejiang province and evaluating the mineral nutritional characteristics of Carya cathayensis fruit can provide a basis for screening Carya cathayensis germplasm resources with high nutritional value.【Methods】Nine kinds of mineral elements including K, Ca, Na, Mg, Zn, Cr, Mn, Fe and Cu in Carya cathayensis kernel were determined by Chinese standard method. The variation degree among different clones was compared by calculating the coefficient of variation(CV) of each mineral element; By calculating the significance index(Sig.) of each element, it was judged whether the mineral nutritional traits of the tested Carya cathayensis clones were formed by artificial breeding intervention rather than natural formation, and Sig.> 0.05 indicated that the data conformed to the normal distribution; By calculating the correlation coefficient between various elements, the possibility of breeding varieties rich in multiple mineral nutrients was evaluated. The quantitative traits conforming to normal distribution and with coefficient of variation ≥ 15% were divided into 5 grades by using( -1.281 8S),( -0.524 6S),(  +0.524 6S) and(  +1.281 8S), and the traits with coefficient of variation < 15%were divided into 3 grades by using( -0.524 6S) and(  +0.524 6S), which were used to evaluate the contents of mineral nutrients among different clones. The process of principal component analysis and cluster analysis in this experiment was completed by psych package of R software and SPSS software.The principal components were extracted through the principal function in psych package(the first n principal components with a total variance contribution rate ≥ 85.00%), rotated orthogonally, and scores = true was selected to obtain the score RCkof the sample in each principal component; Combined with the variance contribution rate Ekof the corresponding principal component, the comprehen-nsive score  of the sample was obtained; The principal component score coefficient of each index was obtained through the round function, and then the functional formula between each index and the principal component was obtained; Cluster analysis was completed through the process of“analysis classification system clustering”in SPSS software【.Results】(1)The variation of mineral nutrition characteristics of Carya cathayensis was rich, and the variation coefficient was between 8.93% and64.51%, among which the larger ones were Cr(64.51%), Na(45.73%), Mn(23.90%) and Fe(19.75%).The larger the variation coefficient was, the higher the seed selection value of this element would be among the tested clones.(2) The results of normality test showed that the Sig. values of nine mineral elements were between 0.131 and 0.991, which accorded with the normal distribution, indicating that the content of mineral elements in hickory was affected by many small independent random factors.(3) The correlation matrix showed that there was a highly significant positive correlation between K and Mg(0.619), and a significant positive correlation with the contents of Cu(0.527), Zn(0.520), Ca(0.442),Cr(0.345) and Fe(0.365). Ca was positively correlated with Zn(0.680), Mg(0.586) and Cu(0.541); Na was positively correlated with the content of Cu(0.617) and Zn(0.528); Mg was positively correlated with the contents of Cu(0.838), Zn(0.835) and Fe(0.570); There was a highly significant positive correlation between Zn and the contents of Cu(0.890) and Fe(0.666); There was a significant negative correlation between Cr and Mn(-0.328); There was a significant positive correlation between Fe and Cu(0.545). The greater the correlation coefficient was, the greater the probability of obtaining clones rich in multiple mineral elements would be at the same time.(4) The results of principal component analysis showed that the contents of K, Ca, Mg, Zn, Cr, Mn, Fe and Cu were integrated into four component factors, and the cumulative variance contribution rate was 88.19%; According to the calculation results of comprehensive components, Dayuan 3, Gaoling 8, Gaoling 3, Xukeng 24 and Xukeng 89 ranked among the top 5 in the comprehensive component scores respectively, and the comprehensive mineral nutritional quality of their fruits was the best.(5) The results of systematic clustering showed that 21 Carya cathayensis clones could be clustered into 3 categories according to the score of comprehensive components, and there was a large distance in mineral nutritional quality among various categories. Among them, 6 clones of Dayuan 3, Gaoling 8, Xukeng 24, Xukeng 88, Gaoling 3 and Dayuan 4 were clustered into class B. The total content of mineral elements was high, and at least two of Cr, Mn and Fe contents with the largest variation range were high.(6) Three mineral element indexes with variation coefficient ≥ 15% were graded with 5-level probability, and five mineral element indexes with variation coefficient < 15% were graded with 3-level probability. The results were basically consistent with the principal component analysis.【Conclusion】In this study, six high-quality clones were selected, including Dayuan 3, Gaoling 8, Xukeng 24, Xukeng 88, Gaoling 3 and Dayuan 4. Among them, Gaoling 8 and Dayuan 4 have the potential to be used as high-quality fruit clones for breeding.