Mungbean (Vigna radiata (L.) Wilczek), also known as greengram, is the most widely cultivated Asian Vigna species. Improved mungbean cultivars have a narrow genetic base that limits yield potential and they are poorly adapted to varying growth conditions in different agro-ecological conditions. The genetic potential of landrace germplasm accessions in gene- banks therefore needs to be better exploited. Germplasm core collections are made of a reduced set of representative accessions from the entire diversity maintained by genebanks. This subset of accessions can be used for testing general combining ability with local germplasm in the search for yield enhancement. Core collections also help breeders in selecting parental material that could maximize potential genetic gain from derived hybrid populations. At the National Bureau of Plant Genetic Resources (NBPGR), India, genetic enhancement/pre- breeding studies in mungbean have been initiated involving diverse parents mainly from the cultivated gene pool, using the Bureau's core collection as starting material. Germplasm enhancement aims at widening the genetic base of breeding materials by transferring desired genes from unimproved germplasm into enhanced varieties. Mild and decentralized selected material was maintained in target sites across the country. A total of 102 progenies were advanced to F5 for further selection and use by the breeders in Delhi. The genetic potential of a few selected enhanced progenies with desired plant types and better yield-related traits is presented in this paper. The study clearly demonstrates the potential of germplasm accessions conserved in genebanks for use in large-scale base-broadening efforts in mungbean.

Mungbean yellow mosaic virus (MYMV) disease is one of the most devastating biotic constraints of mungbean production in India. Dependable knowledge on the number and mode of action of genes controlling resistance to MYMV disease is one of the keys to develop resistant cultivars. The F1s of four crosses derived from four MYMV resistant genotypes × one highly susceptible genotype, their parents, F2s and F3s along with a susceptible check were screened for responses to MYMV disease following the infector-row technique under natural infection conditions. A good fit of F2 population segregation to the hypothesized ratio of 15 susceptible:1 resistant and that of F3 population segregation to the expected ratio of 55 susceptible:9 resistant at 55 days after planting confirmed the involvement of two recessive genes in imparting resistance to MYMV disease.

On the premise that seed ageing may be largely a result of free-radical lipid autoxidation, a study was made of the relationship between lipid stability and longevity in seeds of soybean (Glycine max), lentil (Lens culinaris), mungbean (Vigna radiata), chickpea (Cicer arietinum), broadbean (Vicia faba), pea (Pisum sativum), lettuce (Lactuca sativa), and tomato (Lycopersicon esculentum). Seed lipids were examined for α-, γ- and δ-tocopherols, and levels of unsaturated and saturated fatty acids. Using this information, analysis was attempted using linear, multiplicative or exponential models to correlate aspects of lipid stability with seed longevity values from the published literature. No statistically significant correlations could be found between longevity and total lipid unsaturation, tocopherol levels or two protection formulae obtained from the oil chemistry literature. When values for tomato were excluded, a good correlation (r = 0.89, P = 0.007) was obtained using a multiplicative regression model for levels of linolenic acid per unit of total tocopherols in relation to longevity. Possible factors contributing to a lessening of the relationship between lipid stability and seed longevity are discussed.

Osmotic priming in a polyethylene glycol solution (300 g/kg water) for 48 h resulted in a partial loss of desiccation tolerance for seeds of Vigna radiata (L.) Wilczek (mung bean). The percentage of germination began to decrease after primed seeds were dried down to water contents less than 0.06 g/g DW. As compared with control seeds, primed mung bean seeds also had poorer storage stability. The decline of storage stability after osmotic priming was correlated with the modifications of seed water sorption properties. Priming significantly increased the amount of water associated with the weak water-binding sites, and reduced the amount of water associated with the strong binding sites and multi-molecular binding sites in seed tissues. The enhancement of molecular mobility in seeds, as a result of such water redistribution, probably accelerates seed deterioration and decreases storage stability.

Mungbean seeds are often attacked by bruchid insects causing serious damage to the grain during storage. The susceptible/resistant characteristics of mungbean against bruchids have been investigated at the protein level. Seeds of the susceptible cultivar Osaka-ryokuto and the resistant near-isogenic line BC20 were collected at 5, 9, 13, 17, 21 and 23 days after flowering. Crude, cytosol and membrane protein fractions were extracted from the seeds for twodimensional polyacrylamide gel electrophoresis analysis. In Osaka-ryokuto six proteins were found in higher amounts compared to BC20 in the crude protein extract. Some of these proteins were homologous to legumin B and liguleless1. And in BC20 one unique protein, homologous to SalF1R, was identified. In the subcellular protein fractions, nine unique proteins were identified in BC20, seven in the cytosol and two in the membrane fractions. These proteins were homologous to chitinase, alanine aminotransferase in membrane, and SalF1R, β-1,3- glucanase, protein phosphatase 2A, peroxidase BP 2A, provicilin and canavalin in the cytosol fractions. Previous findings of many researchers reveal that these are mainly defence-related proteins. Thus, it is suggested that the above proteins may play a role in maintaining the resistance of line BC20.

Osmotic priming reduces the longevity of Vigna radiata (mung bean) seeds during subsequent dry storage. The present study has investigated the relationship between volumetric changes, modified water sorption properties and the decrease in seed longevity after priming. Volumetric analysis of control embryos revealed two major dehydration-related volumetric contractions in the biopolymer matrix, reflecting structural reorganization in biopolymer matrix during drying. These contractions occurred at hydration from 0.29 to 0.23 g g–1 dw and from 0.18 to 0.11 g g–1 dw, respectively. Volumetric contractions were reduced significantly after priming and also occurred at higher water contents (i.e. 0.48–0.32 g g–1 dw and 0.21–0.11 g g–1 dw). Consequently, at the same water content, primed seed embryos had higher specific biopolymer volume and lower specific density than control embryos. Water sorption study showed that priming did not change the monolayer hydration value, but altered the properties of multilayer water sorption in seed axes. The analysis of water clustering function suggested that priming enhanced the water–water association in seed axes, but not in cotyledon tissues. Solid-state 1H-NMR (nuclear magnetic resonance) investigation confirmed that priming did not cause a significant change of water dynamic properties in cotyledon tissues at water contents below 0.20 g g–1 dw. The relevance of volumetric modifications of the biopolymer matrix and changes in water clustering function to the reduced seed longevity after priming is discussed. It is proposed that priming-induced increases in surface reactivity may enhance deteriorative chemical reactions in re-dried seed tissues.

In the tropics, insect pests cause considerable damage to soybean, Glycine max and mungbean, Vigna radiata from germination until harvest and even in storage. Agromyzid flies in the seedling stage, lepidopterous and coleopterous defoliators in the vegetative and early reproductive stages, pentatomid and coreid bugs and lepidopterous pod-borers in the reproductive stage, and bruchids in storage all cause significant damage. Sources of resistance to agromyzids in mungbean (AVRDC accession V 4281), defoliators (PI 171451, PI 227687, PI 229358) and stink bugs (PI 227687 and PI 171444) in soybean, and bruchids in mungbean (V 2164) are available. In most cases, antibiosis appears to be the major mechanism of resistance. These sources are being exploited in the development of agromyzid-resistant mungbean, defoliator- and stink bug-resistant soybean, and bruchid-resistant mungbean at the Asian Vegetable Research and Development Center (AVRDC). Diversity in insect species within a pest complex and, in certain cases, biotypes of single pest at different locations as well as pest ecology are likely to influence the resistance reaction and, in practical terms, the utilization of pest resistance as a tool in the management of insect pests of soybean and mungbean. Greater efforts are required at local level to fully utilize insect pest resistant germplasm.