In vitro screening of potato lines for drought tolerance.

Fresh water resources are limited and their use in agricultural production is expected to come under increasing constraints. Eighteen Syrian lines of potato (Solanum tuberosum L.) were screened for drought tolerance by measuring aerial and root growth in vitro. Drought stress was evaluated by adding 2, 4, 6, 8 and 10 % (w:v) of sorbitol to Murashige- Skoog medium and compared to 0 % for the control. Water potential of media ranged from -0.58 MPa to -2.5 MPa. Water-stress in culture adversely affected plant growth, and genotypes differed for their responses. Plant length and stem thickness, leaf area, root number length and thickness, and plant fresh and dry weights and plant water content were measured and all decreased due to drought. Grouping lines by cluster analysis for response to drought resulted in: (1) a tolerant group of six lines, (2) a moderately tolerant group of seven lines, and (3) a susceptible group of five lines. The variation in germplasm indicated that potato varieties can be developed for production under some levels of drought.