Abstract

Citrus propagated by seed and grown on own roots for a long time till the middle of the 19 century, from the second half of 19 century there are different threats encountered citrus growers in various countries of the world and affect citrus production which becomes unprofitability, the problems include biotic stress like spreading root rot disease, Phytophthora spp., and different adverse environmental conditions like high water tables, poor drained soils, drought, salinity, and heat waves which affect negatively on tree growth, productivity, and fruit quality.