‘Superior Seedless’ grapevine grafted on three rootstocks grown on calcare- ous soil under diluted brackish water irrigation. II. Expression of antioxidant genes

Grapevine rootstocks that can absorb brackish water and maintain satisfactory growth of the grapevine scion might be a feasible management practice in areas suffering scarce water resources. The objective of this study was to evaluate the expression of antioxidant genes in ‘Superior Seedless’ leaves grafted on R110 (Vitis berlandieri x V. rupestris), 41B (V. berlandieri x V. vinifera) and P1103 (V. berlandieri x V. rupestris) in response to diluted brack- ish water irrigation at three levels: 1.5, 3.0 and 5.0 dS m-1 in addition to the 0.8 dS m-1 control. Results revealed that after salinity exposure for two weeks, the transcript levels of APX, Mn-SOD and MDAR increased in ‘Superior Seedless’ leaves grafted on the different rootstocks. However, their expression levels in response to salinity were noticeably higher in plants grafted on P1103 and R110 compared to 41B. The expression of CAT gene showed obvious enhanced level in plants grafted on P1103 in response to salt exposure. Meanwhile, the expres- sion of CAT gene in ‘Superior Seedless’ scion grafted on 41B or R110 showed almost unchanged level in control and stressed conditions. Down-regulation of CuZn-SOD was recorded in leaves of ‘Superior Seedless’ grafted on P1103. Slight up-regulation of this gene in response to saline condition was recorded when scion was grafted on 41B or R110. The expression of GPX was enhanced in scion grafted on P1103 and 41B. On the other hand, scion grafted on R110 showed decreased expression of GPX in response to salt treatment. Grapevine root- stocks that have V. rupestris and V. berlandieri in their parentage are good can- didates for salinity tolerance.

‘Superior Seedless’ grafted on three selected grapevine rootstocks grown on calcareous soil under diluted brackish water irrigation. I. Growth performances

Mixing brackish water with conventional quality water for irrigation in ratios to maintain satisfactory vigor of grapevines might be a feasible man- agement practice. The objective of this study was to evaluate the performance of three grape rootstocks that are used worldwide and locally; R110, 41B and P1103, irrigated with three salinity levels: 1.5, 3.0 and 5.0 dS m-1 in addition to the 0.8 dS m-1 control. A randomized complete block design was used with three blocks of 12 pots each. ‘Superior Seedless’ grafted on P1103 showed bet- ter performance regarding chlorophyll content, stem length and number of young leaves and even growth after bud break. It does seem that grapevine rootstocks that have either V. rupestris or V. berlandieri in their parentage are good candidates for salinity tolerance. It can be concluded that irrigation with diluted brackish water can be practiced for a certain period of time (two months from April to June); according to our findings under conditions of the experiment, to be followed by irrigation with good quality water in order to flush excessive salts out of the root zone.