Journal of Advances in Biology & Biotechnology

Citrus is an evergreen subtropical perennial whose long fruit-development cycle exposes orchards to several climatic hazards within a single season. Warming, more frequent heat extremes, altered rainfall, declining irrigation-water quality and episodic freezes now coincide in many producing regions, yet the physiological, genetic and agronomic literature on these hazards has developed largely in separate compartments. This critical narrative review examines how the evidence on combined abiotic stress, rootstock-mediated tolerance and orchard-level adaptation fits together, and how far laboratory and pot findings can support decisions in commercial orchards. Peer-reviewed literature published from January 2000 onwards was identified through international and regional scholarly sources, supplemented by citation tracking, and appraised qualitatively for design, stress realism, scale and transferability. Four conclusions are well supported. First, combined heat and drought produces physiological responses that cannot be predicted from either stress alone, with leaf cooling through transpiration, photoprotection and antioxidant capacity distinguishing tolerant from sensitive genotypes. Second, rootstock rankings are stress-specific and frequently reverse between seedling experiments, grafted pot trials and field orchards, so that no rootstock is broadly tolerant. Third, regulated deficit irrigation applied at less sensitive fruit-growth phases can save water with modest or no yield penalty, although outcomes depend on cultivar, rootstock and stress intensity. Fourth, canopy-level measures such as shade netting, particle films and protective screens alter leaf temperature, water status or pest exclusion, but evidence for their economic value under climate change remains limited. The evidence is weaker for tetraploid rootstocks, whose pot-based advantages have not been consistently reproduced under competition or field conditions, and for elevated carbon dioxide as a buffer, because the long-term enrichment data come from a single well-watered experiment. Major gaps include multi-season field trials combining stresses, standardised stress-imposition protocols, rootstock evaluation across stress types and biotic pressure, and region-specific evidence from tropical and South Asian systems. Adaptation is therefore best framed as matching rootstock, cultivar and management to local hazard profiles rather than as the search for a universally tolerant genotype.