Influence of Parental Soil Moisture Stress during Soybean Reproductive Stage on Seed Germination and Early Seedling Vigor of the Offspring.

Stressful parental environments can vividly influence expression of traits in offspring resulting in poor seed germination and seedling establishment. Maximum seed viability and seedling vigor may be achieved if the parents are grown under optimum moisture conditions during seed formation. The objective of this study was to determine the effect of soil moisture stress during reproductive stage on soybean seed yield, individual seed weight, and the subsequent germination, and seedling vigor of the next generation. Two soybean cultivars; Asgrow 5332 and Progeny 5333 were exposed to five levels of evapotranspiration (ET) (100, 80, 60, 40, and 20% ET) of irrigation treatments under sunlit environmental conditions at flowering stage. In one of the experiments, seeds obtained from these treatments were tested for seed vitality traits at five different in-vitro osmotic stress treatments using polyethylene glycol (PEG 8000) solutions which mimic water potentials ranging from 0.0 to −0.9 MPa with -0.2 MPa increments at 25 °C. Maximum seed germination, time to 50% germination, and seed germination rate were derived by using appropriate regression analysis. In the second experiment, the seeds from parental treatments were subjected to three different soil moisture stress conditions (100%, 66%, and 33% field capacity) under pot culture in rain-out shelters. Several morpho-physiological parameters including root traits were measured at the end of the experiment 25 days after planting. Soil moisture stress caused a substantial effect on seed vigor resulting shriveled, shrunken, and miss-shaped seeds with reduced seed weight. The parental moisture stress environment significantly influenced seed and seedling vigor of the next generation. The results suggest that soil moisture stress induced irreversible change in seed vitality traits and seedling vigor of the offspring of stressed individuals when their parents were exposed to soil moisture stress which could lead to low-quality offspring in the successive generations.