Comprehensive analysis of fruit agronomic traits of 47 pomelos with green skin and red pulp as well as screening of excellent germplasm

Abstract:【Objective】As the fruit characteristics of germplasm resources are diversified, the specific germplasm could be screened out through analyzing of and studying on the fruit traits, which can provide the practical and theoretical basis for evaluation, preservation, variety selection and innovative utilization of pomelos with green skin and red pulp.【Methods】In this study, genetic variability, correlation analysis, principal component analysis and cluster analysis were applied to analyze 12 agronomic traits, such as fruit weight, fruit number, yield of single plant, longitudinal diameter, transverse diameter, fruit shape index, etc, of 47 pomelo germplasm resources. And the excellent germplasm was selected out according to the analysis.【Results】47 pomelo germplasms showed rich genetic diversity, the variation coefficients showed in a descending order: yield of single plant (74.32% ), fruit number (73.24%), red flesh (37.49%), fruit surface green (33.43%), seed number (27.52%), thickness of pericarp (20.95%), fruit weight (19.97%), and number of capsule (10.74%). In correlation analysis, it was showed that there was no significant correlation between number of capsule and seed and other traits, but other traits had mutual influence. It meant that the number of capsule and seed was not representative in variety breeding of pomelo germplasm resources with green skin and red pulp, and the traits such as fruit weight, fruit number, yield of single plant and longitudinal diameter should be considered comprehensively. There were extremely significant correlations between the following traits, for example, fruit weight and longitudinal diameter, widest and transverse diameter; widest and transverse diame-ter, thickness of pericarp and fruit surface green; thickness of pericarp and fruit surface green color, red flesh and fruit surface green color (p＜0.01). And the yield per single plant was negatively correlated with thickness of pericarp (p＜0.05). 12 characteristics were classified into 4 principal components with characteristic vector value being greater than 1. The cumulative contribution rate of the 4 principal components reached 73.733%, which reflected the fruit size, yield, fruit appearance and fruit shape, respectively. Among them, the contribution characteristic value of the first principal component was 30.146%, and the traits with higher load value were fruit weight (0.872), longitudinal diameter (0.872), widest part (0.888) and transverse diameter (0.905). The contribution rate of the second principal component was 18.845%, and the traits with higher load value were fruit number and yield per single plant. The contribution rate of the third principal component was 14.327%, and the higher loading values were red flesh and fruit surface green color. The contribution rate of the fourth principal component was 10.415% , and the traits with higher load value were longitudinal diameter and fruit shape index. In these traits, fruit weight, yield per single plant, fruit surface green color, red flesh and pericarp thickness were the main indexes to evaluate the excellent germplasm resources, which can be used as the main basis in breeding selection. 47 germplasm resources were divided into five groups when the euclidean distance was set to 7.5 by cluster analysis. The first group contains 1 accession, which has very large fruit, pear shape, light red flesh (grade 2) and light green fruit surface (grade 5). The second class contains 11 accessions, which have medium size, with the weight in a range from 0.94 kg to 1.2 kg, medium yield, fruit shape was nearly round, fruit flesh was deep red and fruit surface was deep green. Among them, 421 and 309 showed better comprehensive traits. There are two accessions in class Ⅲ, which have small fruit, thin skin, light red flesh and yellow fruit surface. In class Ⅳ, there are 21 accessions, whose fruit weight ranged from 1.2 kg to 1.4 kg, fruit flesh was dark red (7-9), fruit surface was dark green (5-8), and fruit shape was nearly round (0.96-1.09). In this group 312, 420, 518, 318, 314, 215, 404, and 414 showed good performance. There are 12 accessions in class Ⅴ, whose fruit weight ranged from 1.5 kg to 1.4 kg, nearly round (0.93-1.06), dark red flesh (6-9), and light green fruit surface (1-5). Based on principal component analysis and cluster analysis, 14 accessions with good performance in fruit weight, yield, fruit surface green color and red flesh were screened out from 47 germplasms. Among them, 312 has the best comprehensive performance, followed by 518, 420 and 421.【Conclusion】In this study, 12 agronomic traits of 47 pomelo germplasm resources with green skin and red pulp were analyzed based on diversity analysis, principal component analysis and cluster analysis. Four accessions with good performance were screened out, and the preferred order is 312＞518＞420＞421. In the subsequent variety breeding and utilization, we should combine with the internal quality to choose the appropriate material. The results preliminarily determined the differences in agronomic traits among different varieties of ‘green skin and red core pomelo’, which could provide reference for variety breeding, production and utilization.