THE INFLUENCE OF ROOTSTOCK ON LEAF WATER POTENTIAL, YIELD, AND BERRY COMPOSITION OF RUBY SEEDLESS GRAPEVINES

An experiment was conducted to determine the effect of eight different rootstocks [99 Richter (99R), 110 Richter(110R), Rupestris du Lot (du Lot), 140 Ruggeri (140Ru), SO4, 41B, 101-14, and 1103 Paulsen (1103P) ] on the productivity of non-irrigated Ruby Seedless grapevines grown in Morocco. Measurements taken over a three-year period included fruit growth and maturity indices, yield, and pruning weights. Leaf water p otential (psi(L)) was measured at various times during the second year of the study. Results indicated that midday psi(L) declined throughou t the season for all rootstocks, averaging -0.9 MPa at fruitset and -1 .3 MPa at fruit maturity. The diurnal time course of yr, averaged acro ss ail rootstocks was approximately -0.4 MPa before sunrise, -1.2 MPa around solar noon, followed by a recovery to -0.6 MPa shortly after su nset. An analysis of seasonal, midday psi(L) indicated two extreme gro ups of rootstocks: du Lot and 110R had more negative leaf water potent ials than 41B and 1103P. The difference between the two rootstocks wit h the greatest and the least negative average psi(L), du Lot and 1103P , respectively, approached 0.2 MPa. Derry weight was greatest for vine s on SO4, 99R, and 41B, and lowest for 101-14 and du Lot. At maturity, the lowest fruit soluble solids concentration was obtained on 99R and 41B while the lowest fruit coloration was obtained on 110R, du Lot, 1 40Ru, and 41B rootstocks. These results demonstrated that rootstock ha d a significant effect on Ruby Seedless fruit characteristics under no n-irrigated conditions.