EFFECT OF DIFFERENT LEVELS OF WATER STRESS AND HUMIC ACID APPLICATION ON YIELD, ITS COMPONENTS AND GENOTYPIC STABILITY OF SOME NEW LINES OF GURMA WATERMELON (Citrullus colocynthoides)

Because saving irrigation water became a necessity recently, tolerant cultivars and different water management practices should be explored. Hence, two field experiments were carried out in a clay loam soil at Barramoon experimental farm, Hort. Res., Institute, Dakahlia Governorate, Egypt, during the two summer seasons of 2011 and 2012 to examine differences in yield and yield components among three new lines of gurma watermelon under three irrigation conditions (normal irrigation (4 irrigations), withholding last irrigation and withholding last irrigation with addition of humic acid), and to determine the lines stability for the different yield traits across irrigation conditions and identify the adapted lines. The results indicated that all studied traits were significantly decreased under water stress withholding last irrigation. But, adding humic acid in water deficit conditions increased significantly all studied characters more than under stress conditions in both seasons. Line s₂ had significant more number of fruits per plant, seed yield per plant, 100-seed weight and seed yield per fedden than the other two lines in both seasons. The interaction between irrigation conditions and lines had significant effects on all studied traits in both seasons. On the other hand, the stability analysis showed that the mean sum of squares due to genotypes and genotypes x environment (linear) indicated significant values for all studied traits. The variances due to environment + (varieties × environment) and environment (linear) were significant for all studied traits except number of fruits per plant. On the basis of stability parameters, S₂ was found to be most stable genotypes for yield attributing traits with high mean performance across different environments. Thus, this line can be used as new variety, also, it can be exploited in future breeding programs to develop high yielding and stable genotypes for water deficit conditions.