Improving abiotic stress tolerance in black gram

Abstract

Salt stress is a major abiotic stress adversely affecting the yield of Vigna mungo (blackgram), an important pulse crop. In conjunction with cereals, it satisfies the dietary protein requirements of the predominantly vegetarian Indian population. Because of a narrow genetic base in pure-line selections and limited natural variation for desirable characteristics, a viable option for improvement of blackgram is through genetic engineering. The focus of our study has been on engineering salt-tolerance in blackgram by the over-expression of the Glyoxalase 1 (Gly 1) gene. Efficient regeneration systems have been established in V. mungo using different explants. Binary vectors were constructed wherein the Gly 1 gene was placed under the control of a constitutive (cestrum virus) and a salt-inducible promoter (rd 29A) respectively. The selectable marker gene (kanamycin resistance) in these vectors was flanked by lox sites so as to enable its excision following the recovery of transformed plants. Vectors containing the phosphomannose isomerase (PMI) gene were also used for transformation of V. mungo. Putative transformants showed tolerance to 600 mM NaCl and 10 mM methyl glyoxal, the substrate of glyoxalase 1 enzyme, compared to untransformed controls which did not survive on more than 200 mM NaCl and 5 mM methylglyoxal. They tested positive with the Gly 1, kanamycin and GUS primers. The transformants carrying the cre gene are being developed to cross with those containing the loxed kanamycin gene to obtain salt-tolerant marker free plants.