Temperature and Water Deficit Effects on Storage Root Initiation and Growth of Sweetpotato.

Drought and temperature are the two major abiotic stresses affecting sweetpotato growth and development, particularly storage roots. Yet little quantitative information between these environmental stresses and plant growth and development are available. Two experiments were conducted to quantify the effects of temperature and drought using the cultivar, Beauregard. Experiment one was carried out in sunlit plant growth chambers by varying day/night temperatures, 20/12, 25/17, 30/22, 35/27, and 40/32°C, under optimum moisture and nutrient conditions. In Experiment II, soil moisture was varied using sensor-based irrigation, 100, 80, 60, 40, and 20% of field capacity. In both the experiments, plants were destructively harvested at regular intervals staring 15 days after transplanting. Total and storage roots and biomass were recorded. Total root numbers were significantly increased with increase in soil moisture levels. Storage root numbers, however, were slightly higher at 60% soil moisture level and declined at high and low soil moisture levels. Minimum time required to form 50% of the storage roots was about 20 days under 60 and 80% soil moisture levels, and more days were required at higher levels of soil moisture conditions. Vine lengths and weight of total plant and storage roots decreased significantly with decreased soil moisture levels. Temperature, when imposed at the beginning of planting, did not significantly affect either total or storage roots formed. The time to reach 50% of storage roots, however, was significantly affected by temperature and the response was quadratic with minimum time required at 35/27°C. Total biomass produced increased up to 30/22 and 35/27°C and declined slightly at the 40/32°C. Storage root biomass increased with increase in temperature up to 30/22°C, and declined by 11 and 90% at 35/27 and 40/32°C, respectively. The functional algorithms developed from these data sets will be useful in predicting sweetpotato storage root formation and growth.