Genetic Diversity Analysis And Founder Parents Selection Of Hevea Brasiliensis Cultivars Released In China

Hevea brasiliensis is native to South America,and it is a kind of typical tropical plants. Currently, in addition to the Amazon Basin countries, the major rubber tree cultivated coutres including Thailand, Indonesia, Malaysia,Vietnam and other Southeast Asian countries; a few Asian countries such as China, India, Sri Lanka;Nigeria and a few other African countries.The rubber tree breeding work of China began in 1954. In order to catch up with the advanced level of the world rubber tree breeding, to meet the needs of the development of the rubber industry in China, breeders determined the rubber tree breeding objectives, that was to carry out the study of cross-breeding between the foreign superior varieties.The objective was based on the introduction of foreign superior clones and aimed at the ecological environmental characteristics of the rubber cultivated area.Being as Hybrid parents,founder parents bred many excellent varieties, and played an important role in the breeding area. In this study, EST-SSR molecular markers combined pedigree analysis and morphological traits of varieties were used to analyse and reveal the genetic diversity of Chinese cultivated rubber trees and the genetic contribution of different parents to their offsprings. The founder parents of the rubber tree were selected preliminarily that will provide prerequisite for the use of founder parents and provide a theoretical basis for selection and breeding work of Chines rubber tree.The main results were as follows:1. Based on pedigree analysis to uncover the genetic relationship of Chinese cultivated rubber tree, the results show that the PR 107, RRIM600, PB86, GT1 are important ancestors in Chinese rubber tree breeding. The number of their self-sterile Offspring varieties are much higher than the offspring of other parents,and the nuclear genetic contribution this four parents to their directly offspring ranked the top 4.2. Quality and quantitative characters of 175 Chinese cultivated rubber tree were made statistic, the data analysis showed that there is a great difference between different varieties.The average value of variation coefficient of nine Qualitative traits is 45.34% and indicate these traits are important differentiation markers. The average value of variation coefficient of nine Quantitative traits is 28.61%, The variation coefficient of Cold hardiness is the largest and up to 65.42%, followed by the lowest coefficient of variation of the wind resistance, dry rubber content, growth rate, yield traits. The principal component analysis showed that the first 10 principal components contribution rate reach 86.13%,and thus the first ten principal component can represents most information of all agronomic traits and can be used to conduct a comprehensive evaluation of the material.3. Comprehensive genetic contribution of parents and the character of their offspring, the analysis results show that PR107、RRIM600、GT1、PB86 have their owen good character and good genetic stability being as parents,they are founder parents in Chinese rubber breeding.4.104 rubber tree varieties clustering based on phenotypic traits, all the tested rubber tree varieties are divided into three categories, the third category can be subdivided into 10 sub-categories, part of the tested cultivars cluster together according to Pedigree most of according to phenotypic characteristics.5.57 EST-SSR markers were selected from 224 pairs of primers to analyse Polymorphism.PIC,He,H is respectively 0.4625,0.4758,0.5208, the results show that the Rubber tree loci detected by 57 EST-SSR is moderate polymorphism6. Genetic identity of 104 parts of rubber tree germplasm materials ranging from 0.3387 to 0.9829. The average of all pairwise genetic identity is 0.6246,and this demostrate most of the tested materials have small genetic difference which coincide with the fact the rubber tree have narrow genetic base.7.104 cultivated rubber trees cluster by UPGMA method using 57 EST-SSR primers, most of the tested varieties together in accordance with the pedigree, is divided into five major categories.8. Using EST-SSR marker to analyse of the four rubber tree founder parents and their derivative varieties, analyze and explore the founder parental gene transmission capacity of different chromosome regions to their offspring. Data analysis results show that the alleles of PR 107, RRIM600, GT1, PB86 get a good pass to their offspring.