Physiological response of Conilon coffee clone sensitive to drought grafted onto tolerant rootstock

The objective of this work was to determine alterations in physiology and those due to drought tolerance on Conilon coffee (Coffea canephora) contrasting clones regarding the sensitivity to hydric stress. The reciprocal grafting between clones 109A, drought sensitive, and 120, drought tolerant, - 120/109A, 120/120, 109A/120, 109A/109A - along with their ungrafted control plants (109A and 120) were evaluated. Plants were cultivated in 12-L vases in greenhouse. Six months after grafting, half of the plants was subjected to water deficit, by suspending irrigation until leaves reached the hydric potential of -3,0 MPa. When clone 120 was used as rootstock, plants presented deeper roots, although with lower root-biomass, higher ability to postpone leaf dehydration and higher instantaneous water-use efficiency (WUE). Under severe drought, starch and sucrose contents decreased similarly, regardless of the treatment, whereas leaf concentrations of glucose, fructose, total amino acids and proline were higher in non-grafted 109A, 109A/109A, and 120/109A plants. These plants showed the lowest WUE values. Solute accumulation was not primarily related to drought tolerance. The use of drought tolerant rootstocks improves to drought tolerance in coffee.