Main content area

Rootstock effects on water relations of peach tree under contrasting watering conditions

Ghrab, M., Masmoudi, M. M., Mechlia, N. Ben
Acta horticulturae 2014 no.1038 pp. 81-88
cultivars, deficit irrigation, evapotranspiration, field experimentation, growing season, irrigation scheduling, leaf water potential, peaches, plant available water, root hydraulic conductivity, root systems, rootstock-scion relationships, rootstocks, trees, water supply, Tunisia
Water status of trees is affected by evaporative demand, soil water availability and hydraulic conductance of the root system. The objective of this work is to test the possibility of improving water status of peach trees by the choice of the rootstock for variable levels of deficit irrigation. A field experiment was carried out in 2006 and 2008 at the experimental station of INAT-Mornag (36°41'N, 10°15'E) in northern Tunisia with the season-maturing peach cultivar Royal Glory grafted on GF677 and Cadaman rootstocks. Tree water status was characterized by measurements of predawn (ΨPD) and midday (Ψm) leaf water potentials and stem water potential (Ψstem). Trees were subjected to differential deficit irrigation conditions during the two seasons. Total applied water during the irrigation season (April-September) was in the range 30-60% ETc considered as severe-mild deficit level. Water supply indices taken as ratios between cumulated water supply by precipitation and irrigation (P+I) and evapotranspiration (ETo) were defined to represent watering conditions of trees over different periods of time: seasonal (Ks), 30-days (K30), 15-days (K15), and 7-days (K7). During the two years, seasonal water supply indices (Ks) which reflect long term soil water availability, decreased from 1.2-1.3 to 0.4-0.55 between the beginning and the end of the irrigation season. K7 and K15 representing short term conditions, varied from 0.5 to 0 in 2006 and from 0.8 to 0.15 in 2008 showing better watering conditions during the latter year. Values of tree water potential of the considered scion-rootstock combinations were variable under these levels of deficit. Under mild deficit, better tree water status was observed for GF677, with lowest ΨPD and Ψstem values of -0.84 and -1.81 MPa respectively. For Cadaman, the values were respectively 0.10 and 0.13 MPa lower compared to GF677 rootstock. Under severe deficit conditions, values of water potential ΨPD and Ψstem dropped under -1.0 and -2.0 MPa respectively without significant difference between the two rootstocks. It appears that rootstock could be used as a mean to improve significantly soil water use of mid-season cultivars for mild stressed conditions. Investigation of relationships between water supply indices and tree water potential showed a high correlation between Ψstem and Ks which could be adopted as good indicator of tree water status over the growing season and used for irrigation scheduling.