Evaluation of growth, yield and physiological responses of some watermelon accessions to water deficit stress

In order to evaluate the tolerance of watermelon (Citrullus lanatus L.) accessions to water deficit stress, an experiment was carried out in a split plot based on randomized complete block design with three replicates in research filed of university of Zanjan during 2016. Treatments consisted of three irrigation levels 100%, 70% and 50% Crop Evapotranspiration (ETc) and watermelon accessions (Ananasi, Sharif Abadi, Mahbubi and Charleston Gray commercial cultivar). The results showed that water deficit stress significantly decreased leaf area, plant length, fruit yield, stomata conductance and relative water content (RWC), and increased total soluble solids, peroxidase activity and electrolyte leakage. Amount accessions, the highest leaf area, plant length and yield (84.6 ton/ha) was obtained in Mahbubi accession. The lowest electrolyte leakage and the highest RWC was showed in Ananasi accession, and the highest peroxidase activity in Charleston Gray. Water deficit stress decreased fruit number per plant and fruit weight, although water deficit had no effects on fruit number in Mahbubi accession. The increase in water deficit stress, decreased water use efficiency in “Ananasi”, “Sharif Abadi” and “Charleston Gray”, but the highest WUE (54.85 kg.m
-3
) was obtained in “Mahbubi” under water deficit 50% ETc. water deficit had no significant effects on fruit pH. According to the results, “Mahbubi” with 46.9% reduction in fruit yield under water deficit 50% ETc had the lowest reduction in fruit yield compared to other accessions that was higher tolerance accession to water deficit stress.