Genetic Diversity Strategy for the Management and Use of Rubber Genetic Resources: More than 1,000 Wild and Cultivated Accessions in a 100-Genotype Core Collection

Abstract

The rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. Arg.] is the only plant species worldwide that is cultivated for the commercial production of natural rubber. This study describes the genetic diversity of the Hevea spp. complex that is available in the main ex situ collections of South America, including Amazonian populations that have never been previously described. Genetic data were analyzed to determine the genetic structure of the wild populations, quantify the allelic diversity and suggest the composition of a core collection to capture the maximum genetic diversity within a minimal sample size. A total of 1,117 accessions were genotyped with 13 microsatellite markers. We identified a total of 408 alleles, 319 of which were shared between groups and 89 that were private in different groups of accessions. In a population structure and principal component analysis, the level of clustering reflected a primary division into the following two subgroups: cluster 1, which consisted of varieties from the advanced breeding germplasm that originated from the Wickham and Mato Grosso accessions; and cluster 2, which consisted of the wild germplasm from the Acre, Amazonas, Pará and Rondônia populations and Hevea spp. The analyses revealed a high frequency of gene flow between the groups, with the genetic differentiation coefficient (GST) estimated to be 0.018. Additionally, no distinct separation among the H. brasiliensis accessions and the other species from Amazonas was observed. A core collection of 99 accessions was identified that captured the maximum genetic diversity. Rubber tree breeders can effectively utilize this core collection for cultivar improvement. Furthermore, such a core collection could provide resources for forming an association panel to evaluate traits with agronomic and commercial importance. Our study generated a molecular database that should facilitate the management of the Hevea germplasm and its use for subsequent genetic and genomic breeding.

Genetic Diversity and Population Structure of IRRDB 1981 and Wickham Rubber Germplasm Based on EST-SSR

“…Therefore, both populations are often found in the same group in some of the previous reports (Le Guen, Doaré, Weber, & Seguin, 2009;de Souza et al, 2015). One explanation for this is because of Boim area, the location where one collected the majority of Wickham clones, geographically closer to Mato Grosso and in the upstream of Tapajos River flowing through the Boim and Mato Grosso areas.…”

“…The positive estimated fixation index value (F) with values ranging from 0.29-0.37 (Table 3) indicated the allelic frequency heterogeneity among in PN'81 populations were also responsible for the overall heterozygous deficiency. These ideas were previously proposed by de Souza et al (2015) who indicated the Amazonian rubber germplasm showed the highest number of specific alleles. The F value also indicated the presence of specific genetic background among PN'81 that did not exist in other rubber populations.…”

Biodiversity Studies in Key Species from the African Mopane and Miombo Woodlands

“…Juss.) (Rubber tree) by de Souza and collaborators [88,89], which have established a foundation of molecular markers (microsatellites and SNPs) highly valuable for breeding and conservation programs.…”

Linkage Disequilibrium and Population Structure in Wild and Cultivated Populations of Rubber Tree (Hevea brasiliensis)

“…79 3 Evaluation of the molecular diversity encompassed in rubber tree genetic resources is a prerequisite 80 for their efficient exploitation in breeding and the development of conservation strategies of genetic 81 diversity. de Souza et al (2015) analyzed approximately one thousand cultivated rubber tree 82 accessions originating from various geographic areas in a Brazilian germplasm collection. These 83 accessions were genotyped with 13 SSR markers distributed across the chromosomes of the species, 84 and a total of 408 alleles were identified, 319 of which were shared between groups, while 89 alleles 85…”

“…For this study, we used accessions selected from the germplasm collection previously analyzed by de 99 Souza et al (2015) and a mapping population (PR255 x PB217) previously saturated with SSR 100 markers described by Souza et al (2013) raw data were processed, and SNP calling was performed using TASSEL 5.0 (Glaubitz et al, 2014). 122…”