Effect of water stress on moth bean [Vigna aconitifolia (Jacq.) Marechal] genotypes

Six genotypes of moth bean [Vigna aconitifolia) (Jacq.) Marechal] viz., RMO-40, RMO-257, CZM-99 (early flowering) and CAZRI moth-1, Maru moth, Jawala (late flowering) were subjected to water stress till wilting by withholding of water at the vegetative and flowering stages in a pot culture trial. Water stress decreased the plant water potential (Ψ p l a n t ) and relative water content (RWC) in all the genotypes. The Ψ p l a n t ranged from -1.75 to -1.97 MPa at the vegetative and from -1.77 to -2.10 MPa at the flowering stage in the water stressed plants as compared to -0.40 to -1.07 MPa in the control. Though water stress significantly reduced the contents of total chlorophyll, starch and soluble protein and increased those of reducing sugars and free amino acids at both the growth stages, but the effects of water stress were more pronounced at the flowering stage. Rates of net photosynthesis and nitrate reductase activity were also reduced drastically at permanent wilting point (PWP). Early flowering genotypes consistently displayed less metabolic alterations than late genotypes for all the aforesaid parameters at both the growth stages. However, RMO-40 among the early and Jawala among the late flowering genotypes displayed better drought tolerance than other genotypes. The maintenance of higher photosynthetic rates and better metabolic efficiency in early genotypes under water stress at either growth stages led to significantly less reduction in their seed yield and dry matter production as compared to late flowering genotypes.