Variety identification and genetic relationships of mungbean and blackgram in Thailand based on morphological characters and ISSR analysis

Abstract

Genetic diversity and relatedness were measured in 17 mungbean (Vigna radiata (L.) Wilczek) and 5 blackgram (Vigna mungo (L.) Hepper) genotypes by means of inter-simple sequence repeat (ISSR) analysis and morphological characters. Unweighted pair-group method arithmetic average (UPGMA) analysis of 19 morpho-agronomic characters showed clear separation of the genotypes into 3 major groups; cluster I containing 15 Thai cultivated mungbean varieties and breeding lines, cluster III containing 4 Thai cultivated blackgram varieties, and cluster II containing a mungbean wild relative (subspecies sublobata), a blackgram wild relative (subspecies silvestris) together with an Indian mungbean landrace. Pair wise coefficients of genetic similarity between all genotypes ranged from 0.17 to 0.84 with an average of 0.52. In total, 341 ISSR fragments were amplified for the two Vigna species by ISSR analysis using 18 ISSR primers. The polymorphism revealed with the ISSR primers was 90.6%. The number of amplified fragments varied from 9 to 32, with a size range of 200 - 1500 bp. The average numbers of fragments per primer and polymorphic fragments per primer were 18.94 and 17.17, respectively. Polymorphism information content (PIC) values ranged from 0.23 to 0.37 with an average of 0.31 across all the genotypes. Pair wise coefficients of ISSR-based genetic similarity between all genotypes ranged from 0.70 to 0.99 with an average of 0.86, suggesting quite narrow genetic base of mungbean and blackgram in Thailand that might limit continued breeding success. UPGMA analysis based on ISSR exhibited 2 major clusters; cluster I containing all mungbean genotypes and cluster II containing all blackgram genotypes. It appeared that ISSR was more effective for classification at the species level although no clear separation at the subspecies level was found. All 22 mungbean and blackgram genotypes can be effectively distinguished by only 6 ISSR primers with the highest PIC values, suggesting the applicability of ISSR analysis for variety identification.