Diversity analysis of fruit traits related to yield in Macadamia germplasms

Abstract: 【Objective】The objective of this study was to analyze the phenotypic diversity of the macadamia(Macadamia integrifolia) nuts in order to explore the genetic basis of main fruit traits of macadamia, and to provide reference for macadamia high-yield breeding.【Methods】Forty-five macadamia cultivars around the world were selected and 20 mature fruits of each cultivar were collected for analysis.The fruits of each cultivar were randomly selected from the periphery of the crown of a tree. Twelve quantitative traits of fresh and air-dried nuts of the 45 macadamia germplasm were determined. Two state standards of the quality grade of macadamia and germplasm resources description and data standards were referenced. Clustering analysis and correlation analysis were employed to analyze the phenotypic traits of the nuts of the macadamia germplasms.【Results】The results of variance analysis showed that the coefficient of variation(CV) of the 12 traits related to yield changed from 5.61% to 17.83%,among of which the maximum CV was 17.83% for fruit kernel, whereas the minimum CV was 5.61% for kernel transverse diameter. Correlation analyses indicated that there were complex correlations among the fruit traits, and the yield was affected by multiple traits. The fresh fruit weight was significantly and positively correlated with the shell weight and the kernel weight. Principal component analysis showed that the fruit related traits were summarized into three principal components and the cumulative contribution rate was 79.55%. The first principal factor was mainly related to the green weight and the shell weight; the second was mainly related to the kernel and the third was mainly related to the nuts. In addition, the 45 macadamia germplasms were divided into three groups based on the cluster analysis. The group Ⅰ was characterized by large and nearly spherical fruit. The group Ⅱ was characterized by ovoid fruit. The group Ⅲ was characterized by small fruit with high seed yield.【Conclusion】There were clearly significant differences among different macadamia germplasm. The green weight, the shell weight,the seed percentage, the shell fruit, the nuts and the kernel could be used for evaluating macadamia nut quality. The results of this study indicated that the fruit traits related to yield in macadamia germplasms had rich diversity, which would lay a basis for genetic improvement and breeding of fruits in macadamia.