Sontichai Chanprame

New microsatellite markers isolated from mungbean (Vigna radiata (L.) Wilczek)

In this study, we reported the isolation and analysis of new polymorphic microsatellites in mungbean (Vigna radiata (L.) Wilczek). Twelve out of 210 primer pairs screened in 30 mungbean accessions gave polymorphism. The polymorphic markers detected two to three alleles per locus with an average of 2.08. Observed heterozygosity varied from 0 to 0.133, while expected heterozygosity ranged from 0.095 to 0.498. Tests for Hardy–Weinberg equilibrium (HWE) and pairwise linkage disequilibrium of the polymorphic loci revealed that all loci except MB‐SSR14 significantly departed from HWE and four pairwise combinations, viz. MB‐SSR14 vs. MB‐SSR42, MB‐SSR42 vs. MB‐SSR87, MB‐SSR114 vs. MB‐SSR121, and MB‐SSR175 vs. MB‐SSR231 significantly deviated from linkage disequilibrium. The markers are being used to study genetic diversity and genome mapping of mungbean.

Inheritance of resistance to iron deficiency and identification of AFLP markers associated with the resistance in mungbean (Vigna radiata (L.) Wilczek)

Iron deficiency chlorosis (IDC) is a major problem reducing yield of mungbean in many countries. In this study, we crossed “KPS1”, the most popular Thai mungbean cultivar susceptible to IDC with “NM10-12”, a mungbean line from Pakistan resistant to IDC. Segregation analysis of the F2 population revealed that the resistance is controlled by a major gene (IR) with dominant effect. Two AFLP markers, E-ACT/M-CTA and E-ACC/M-CTG were identified closely linking with the IR gene. The frequencies of these markers were assessed in 241 mungbean accessions from several countries. The accessions could be divided, in relative to total chlorophyll content of the resistant check (NM10-12) and the susceptible check (KPS1), into the resistant group with 125 accessions and the susceptible group with 116 accessions. Among 125 resistant accessions, E-ACT/M-CTA and E-ACC/M-CTG were present in 119 (95%) and 109 (87%) accessions, respectively. Both markers can identify all resistant accessions from England, Indonesia and Pakistan, but only E-ACT/M-CTA linked to all resistant accessions from Australia, India, Iraq, Taiwan and Thailand. Understanding the inheritance and identifying molecular markers linking to the IR gene can help plant breeders to improve this crop for growing in iron-deficient soils.

Development of tetraploid plants from an interspecific hybrid between mungbean (Vigna radiata) and rice bean (Vigna umbellata)

Mungbean (Vigna radiata) and rice bean (V. umbellata) (both species 2n = 2x = 22) have desirable traits that complement each other. In this study, we rescued embryos from a cross between mungbean cv. “Kamphaeng Saen 2” and rice bean cv. “Miyazaki” and resolved the hybrid sterility problem by colchicine treatment. The interspecific hybrids were obtained when Kamphaeng Saen 2 was used as the female parent. Four out of 80 immature seeds at 12 days old were able to germinate on an MS medium supplemented with 1 mg L−1 IAA, 0.2 mg L−1 kinetin, and 500 mg L−1 casein hydrolysate. Forty random amplified polymorphic DNA (RAPD) primers were screened for polymorphism among the parents, and two specific primers were finally chosen for testing of hybridity. Using the two primers, all putative F1 hybrids were confirmed as the interspecific hybrids. To observe their fertility, some of the hybrid seedlings were transplanted. The hybrid produced flowers profusely but failed to set pods. To overcome the sterility, plants were induced to become tetraploid by colchicine treatment in vitro. The ploidy level of the regenerated seedlings was confirmed from leaf DNA using a flow cytometer. Three out of 20 hybrid seedlings (15%) were successfully induced from diploid to tetraploid by a colchicine concentration of 2 g L−1. The tetraploid hybrids were able to produce flowers and set pods normally.