Effect of exogenous application of glycine betaine on tomato plants subjected to salt stress

摘要

Over the last decades, extensive agricultural activities in Lebanese coastal regions have pushed farmers to search for new water sources from wells. Excessive pumping has caused sea water intrusion, causing irrigation water salinity and altering physiological development of cultivated crops including tomato. An experiment was conducted in order to explore the effect of glycine betaine (GB), a natural osmoprotectant, on tomato salt tolerance. The effect of 2 factors: salinity of irrigation water (SI:2 dS m-i, S2: 4 dS mi, S3: 6 dS mi, S4: 8 dS m and S5: 10 dS m-i) and GB application (GBO: 0 g L- GB1:4.5 g L1, GB2: 6 gL1 and GB3: 7.5 g L-i) was evaluated on tomato ('Sila'J plants. Control consisted on non-treated plants (GB0/S1, GB0/S2, GB0/S3, GB0/S4 and GB0/S5). Effects were evaluated on various parameters such as plant height, leaf number, stem diameter, flowering and fruiting characteristics on several consecutive dates of data collection. Results showed that the positive effect of GB application was limited to some salinity levels. Leaf number (55 DAT) was enhanced in GB2/S1 by 15% compared to GB0/S1. Stem diameter, number of flowers (31DAT) and number of fruits (52 DAT) were improved by 24, 25 and 33% at GB2/S4 compared to GB0/S4 respectively. Number of clusters, fruit set, weight of individual fruit, yield and fruit diameter were negatively affected by increasing salinity levels with no evident effect of GB. Contrastingly, GB3 delayed fruit ripening. Root mass fraction increased at GB2/S1by 33% compared to GB0/S1. While GB application had occasionally a positive effect on some indicators, it did not enhance tomato production under salt stress.