Allelic Diversity Revealed Through SSR Polymorphisms at the Locus Encoding HMG-CoA Reductase in Rubber (Hevea brasiliensis)

This study was carried out to define the extent of allelic variation of 3-hydroxy-3-methylglutaryl-CoA reductase gene (HMGR) in wild Hevea accessions, based on SSR polymorphisms existing at their 3’-untranslated regions (UTRs). Existence of two microsatellite alleles and their repeat compositions was demonstrated earlier in cultivated rubber clones. Both alleles contained perfect poly (AG)n repeats interrupted by a short sequence of 12 nucleotides and allelic variation at this microsatellite locus was the result of repeat length polymorphisms. In wild populations of rubber, nine microsatellite alleles (‘A’ to ‘I’) were identified at the HMGR locus revealing a wide allelic diversity compared to cultivated clones. Out of nine, four alleles (‘B’, ‘C’, ‘D’ and ‘G’) were present in higher frequencies than the others. In total, 15 allelic combinations were noticed for HMGR among wild accessions and four of them were unique. Twenty-five out of 60 wild accessions were found to be homozygous for the above four alleles (‘BB’, ‘CC’, ‘DD’ and ‘GG’) and the rest were heterozygous, characterized by 11 different allelic combinations. Repeat-length polymorphisms were noticed in these four alleles prevailing among wild Hevea accessions. Genetic relatedness of Mato Grosso accessions with cultivated Hevea clones, as revealed through this study, is in agreement with earlier reports on phylogenetic studies using molecular markers. This work is a significant step towards understanding the functional variability of HMGR for latex production in Hevea brasiliensis.