Evaluation of Citrus Rootstocks against Drought, Heat and their Combined Stress Based on Growth and Photosynthetic Pigments

The change in weather patterns around the world has exposed the living world to a variety of stresses, among which heat and drought stress are alarming ones.In citrus, the rootstocks control several morphological, physiological, genetic and production traits of scion cultivars.The current study was conducted to evaluate ten modern citrus rootstocks including two local commercial rootstocks (Rough lemon and Sour orange) against heat and drought stress based on visual assessments, plant growth, dry matter yield, chlorophyll a, b and carotenoid contents.The level of heat and drought were control, moderate and severe stress.All plants at severe combined heat and drought stresses died within five days.Brazilian sour orange showed no change in leaf color under heat and drought stress and regarded as tolerant rootstock.Sovage citrange and Yuma citrange (trifoliate citrus) were sensitive rootstocks and shed their leaves.Plant growth attributes e.g., plant height and root length higher in Brazilian sour orange and low in Sovage citrange.Brazilian sour orange showed high shoot and root dry matter yield.The contents of chlorophyll a, b and carotenoids, were high in Brazilian sour orange followed by Keen sour orange but low in Sovage citrange and Yuma citrange.It is concluded that out of ten rootstocks Brazilian sour orange was proved as tolerant and Sovage citrange as the most sensitive rootstock against drought and heat stress.Brazilian sour orange can be used as rootstock for commercial scion cultivars to evaluate growth and productivity in water deficit and high temperature subtropical areas for sustainable citrus industry.