In vitro response of promising tomato genotypes for tolerance to osmotic stress

Drought is a major abiotic factor that limits plant growth and productivity. Tomato is an important vegetable crop and area under production is limited by irrigation water scarcity. Four cultivars of tomato were grown as callus cultures under conditions of water stress, which was induced by addition of polyethylene glycol (6000) in the medium. The presence of PEG in the medium decreased relative growth rate and increased dry matter content in all treatments compared with the control. In all cultivars, proline levels increased in response to water stress. Also, there was decreased shoot induction in all cultivars with increase PEG treatments. The number of shoot forming in PS-10 and Peto was higher then Roma and Nora cultivars. This result can be used for in vitro screening and manipulations of tomato cultivars for improvement of drought tolerance