Physiological Response of Avocado (Persia americana M.) Seedlings under Seedling Rootstocks to Drought Stress under Shade House Conditions

Avocado (Persea americana M.) is one of the most valuable fruit crops in food and oil industry. However, the productivity of the plant is mainly affected by crop management including propagation, and biotic and abiotic stresses. Among the abiotic factors, drought stress is one of the most important factors that adversely affect avocado growth and productivity. The objective of the study was to determine the physiological response of seedlings of avocado races to different drought stress levels. In this experiment, seedling rootstock from Mexican, Guatemalan and West Indian races were used. For this purpose, drought stress levels (30%, 60% and 100% at field capacity (FC)) were combined and laid down in completely randomized complete design with three replications. The result revealed that, races significantly differed for physiological parameters. The race Mexican was higher in stomata length, stomata number and stomata opening. Oppositely, West Indian race was lower in all physiological parameters except stomata number. Regarding to drought distress, stomata length and opening, photosynthesis rate, stomata conductance and transpiration rate were influenced by the main effect of drought stress and race. Additionally, grafted seedling length, photosynthesis rate, transpiration rate, stomata conductance and instantaneous water use efficiency were influenced by the interaction of races and drought stresses. Mexican race grown under100% FC (control) condition was higher in all physiological parameters except instantaneous water use efficiency. Generally, the present study indicated that seedling grafted with Mexican seedling rootstock race under 100% FC (control) condition performed best. Mexican scions were better under drought conditions.