SEED POLYMORPHISM OF RHYNCOSIA CAPITATA (ROTH) DC. ENHANCE ITS TOLERANCE TO VARYING TYPE AND INTENSITY OF SALT STRESSES

Increasing soil salinity due to climate change complicating weed management. Rhynchosia capitata is becoming an increasing problem in summer crops, such as cotton, soybean, pearl millet and mungbean worldwide. Study was conducted to evaluate the impact of four types of salts stresses (NaCl, Na2SO4, CaCl2 and NaHCO3) at six different levels (0, 50, 100, 150, 200 and 250 mM) on R. capitata seeds of different sizes including small, medium and large. Results revealed that R. capitata can germinate over a wide range of salt stress but as the salinity level was increased to 250 mM the germination percentage and seedling growth decreased significantly. Larger seeds have more potential to germinate and grow vigorously at an increased salt concentration as compared to medium and small seeds. Salt stress caused 40-73%, 59-96% and 40-100% inhibition in seed germination, seedling length and dry weight, respectively. Among various salt stresses CaCl2 showed less inhibition of R. capitata. The higher tolerance of this weed to wide range of salt stresses is alarming factor under current and anticipated increase in salinity, as it will disturb management plans by changing critical completion period and threshold level due to more adaptability of weed under stress than crop plants.