Effect of Water Deficit at different Stages of Development on Forage Yield of Cowpea (Vigna unguiculata L.) Genotypes

The present study was evaluated fourteen populations of cowpea at Farm of Agriculture Research Station Ismailia, Ismailia Governorate, Egypt. These populations were collected from different regions including one check variety. These were investigated under three levels of watering (100%, 75% and 50% of field capacity), for forage yield, genetic variability and association characters during two successive summer seasons 2017 and 2018 using a Randomized Complete Block Design in a split plot. Analysis of variance was revealed significant variation (P < 0.05) among cowpea genotypes for plant length, number of shoots/plant, dry matter percent, forage fresh and dry yields/plot, expected forage fresh and dry yields/fad and water use efficiency. The irrigation levels had non-significant effects on remain traits {i.e.: plant length, number of shoots/plant in the second season, leaf/stem ratio, dry matter percent, forage fresh and dry yields/plot, expected forage dry yield/fad and water use efficiency}. Moreover, the irrigation levels and cowpea genotypes-interaction had highly significant differences for the studied traits, excepting of number of shoots/plant. Among the fourteen cowpea genotypes through the three irrigation levels, over two seasons (2017 & 2018); the Kenyan genotype named KF-122 was produced significant more crude protein (24.20%) and crude fiber (27.60%), whilst, this genotype; IN-1-14 was produced significant less crude protein (12.20%) and crude fiber (13.90%), furthermore the, the cheek Egyptian genotype named "Buff" was recorded, approximately, average aforementioned value over two seasons. The phenotypic variance (d²p) and phenotypic coefficient of variation (PCV %) were slightly higher than corresponding genotypic variance (d²g) and genotypic coefficient of variation (GCV %) for the quantitative forage characters of cowpea indicated the presence of less environmental effect (d²e and ECV %) upon the concerned characters. Heritability in broad sense estimates was moderate to high for all studied traits