Phosphorus Response and Amino Acid Composition of Different Green Gram (Vigna radiata L.) Genotypes from Myanmar

Mungbean or green gram (Vigna radiata L.) is an important component of rice-based cropping systems in Myanmar, where grain yields of around 800 kg ha^(-1) are much below its yield potential of 3000 kg ha^(-1). The reasons for this shortfall are as under-investigated as is the genotype-specific response of this crop to phosphorus (P) application, which is critically low in many Myanmar soils, and the genetic variation in grain quality. For green gram quality, the concentration of lysine, an essential amino acid is particularly important given its scarcity in many cereal-based diets of Southeast Asia. The purpose of this study therefore was to investigate the effects of P application on the root and shoot growth, yield and its components for a range of green gram varieties, and to analyse the protein concentration and amino acid composition in green gram seed of different origins. To this end from 2001 to 2003, field experiments were conducted under rain-fed conditions in Yezin and Nyaung Oo. Fifteen landraces and five introduced green gram cultivars were grown at two levels of P (0 and 15 kg ha^(-1)). There were large genotypic differences in P effects and a significant interaction between green gram genotypes and P for shoot and root growth. An unexpected benefit of P application was a reduction of pest and plant virus infestation in the field. Significant genotypic differences in the amino acid profile of seeds were also observed. The results indicate the potential for breeding efforts to increase seed yield and protein quality in green gram