Development of physiological indices for screening dehydration tolerance in Eucalyptus clones under nursery conditions

An immediate concern of commercial tree plantation is the depleting water resource and drastic change in climatic conditions, which adversely affect the biomass productivity. Maximizing productivity from the available water and nutrient resources is presently the focus of most tree breeding and plantation programs. In Eucalyptus species variations in response to water deprived conditions are reported between species, among provenances and between clones. In the present study, 126 clones derived from the breeding program of Eucalyptus camaldulensis James. and Eucalyptus tereticornis sm. were screened for their response to progressive dehydration stress under controlled environmental conditions and morpho-physiological changes were recorded. Specific Leaf Area (SLA) and Relative Water Content (RWC) were found to be effective dehydration stress indices in both the species. Drought Susceptibility Index (DSI) which measures the decrease in yield of a genotype under drought conditions with respect to mean reduction of all genotypes studied, is a major selection criteria and quantitative indicator in selecting varieties for dehydration tolerance. DSI was recorded for each measured traits and SLA-DSI and RWC-DSI clustered the clones based on their tolerance/ susceptibility to dehydration stress. Additionally, ten prospective clones were selected as dehydration tolerant genotypes and are probable candidates for future multi-environment evaluation under arid and semi-arid conditions for deployment in plantation and breeding programs.