Analysis of fruit characteristics and nutrients of 10 accessions of Macadamia integrifolia

Abstract:【Objective】The variation characteristics of the seed shape, nutrient composition and content of Macadamia nut were systematically evaluated in order to provide a scientific basis for the effective selection and comprehensive development and utilization of Macadamia nuts.【Methods】According to the tree vigor and fruit yield phenotype, 10 accessions of germplasms were selected from 45 accessions of Macadamia nut germplasms, namely GR1, JW, B7, B4, B3, A4, HJ, A16, A38, SH. 20 normal fruits were harvested from the four directions of the outer periphery of the crown of a tree, three repeats were made and a total of 60 seeds were extracted for each germplasm. The fresh fruit weight, shell fruit weight and kernel weight were determined with an electronic balance, and the seed rate and kernel rate were calculated. The vertical and horizontal diameters of fresh fruit, shell and breadth, and the diameter of nuts were determined by the electronic digital caliper (0-100 mm) to measure. Seed rate/% = (shell fruit weight/fresh fruit weight) × 100; kernel rate/%= (per fruit Kernel dry weight/dry shell fruit weight) ×100. The shell fruits and kernels were dried at 45 ℃ for 48 h, and 55 ℃ for 72 respectively, and then the dry shell fruit weight and kernel weight were measured when the moisture content of the kernel was the mass fraction (1.5%±0.5%). At this time, the dried husks were cooled and weighed, and after remov-al of the husks, the dry nuts were weighed. 10 macadamia germplasm characters and nutrients were ana-lyzed by the methods of variation analysis, correlation analysis and principal component analysis (PCA) based on the national standard of China by SPSS 25.0. The nutrients included K, Ca, Mg, Fe, Zn, P, sol- uble sugar, protein, fat, and total amino acids. The measurement was made according to the national standard for the content of ingredients in foods.【Results】There were significant differences among macadamia germplasms in all measured items. The coefficient of variation of the kernel weight was the largest (24.23%), the nut diameter was the smallest (6.04%) among the quality traits, the variation coef- ficient of Ca was the largest (24.47%), and the smallest was fat (2.93%) among the nutrients. The nutri- tional content of nuts was mainly fat. GR1 had the highest content (78 g·100 g-1), and A4 had the lowest content (69.90 g · 100 g- 1). Analysis of the correlation between the fruit characteristics and nutrients of the nut seed showed that the quality of single fruit weight was significantly positively correlated with the single nut weight, the transverse diameter of FW (fruit weight) and the vertical diameter of FW, and positively correlated with the transverse diameter of NW (nut weight). The single nut weigh was signifi- cantly positively correlated with the transverse diameter of NW and the vertical diameter of NW. There was a significantly positive correlation between the seed rate and the K content, and a significantly neg- ative correlation between the seed rate and the transverse diameter of FW. The nutlet weight was nega-tively correlated with the contents of Mg and P. The Ca content was significantly positively correlated with the content of soluble sugar. The Mg content was significantly positively correlated with the con- tents of Zn and P. There was a significantly positive correlation between the content of protein and the content of amino acids. The Zn content was significantly positively correlated with the contents of fat and amino acids. In addition, the results of PCA showed that 90.793% of the observed variability was explained by the 5 components. Based on the 5 common factors and their variance contribution rate, the comprehensive quality ranking of germplasm was calculated, and the top five germplasms were GR1, HJ, JW, B3, and B7.【Conclusion】The fruit characters and nutrients of different macadamia germplasms were different, and these differences were the basic factors for the selection of macadamia variet-ies. The indicators of the vertical diameter of fresh fruit, the transverse diameter of fresh fruit, the single nut weigh, the vertical diameter of nut, the drying quality of shell fruit, ernel rate, the contents of amino acids, soluble sugar, calcium and zinc could be used as representative indicators for evaluating the quali-ty of macadamia germplasms by PCA. HJ, B4, GR1 had the highest fruit weight, JW, A4 had the high- est contents of amino acid, P, and kernel yield. GR1 had the highest fruit quantitative traits, B4had the highest contents of soluble sugar and Ca. HJ and B7 had the highest fruit mineral elements. Three high-quality germplasms (GR1, HJ and JW) were finally screened.