Assessing Drought Tolerance of some Faba Bean (Vicia faba L.) Cultivars Using Genetic Variability, Tolerance Indices and ISSR Markers

This work was carried out for studying the drought tolerance ability of five Egyptian faba bean cultivars (Sakha 1, Sakha-4, Nubaria-1, Giza-716, and Giza-843). Cultivars were planted under three levels of field capacity (FC);100% ,75% and 50% FC respectively with split-plot design in two winter seasons; 2019/2020 and 2020/2021. Growth, yield and its attributes characters, chlorophyll content were measured. Stress tolerance indices (geometric mean productivity (GMP), drought susceptibility index (DSI), mean productivity (MP), yield stability index (YSI), and tolerance (TOL) and genetic variations were calculated. Five primers of Inter-Simple Sequence Repeat (ISSR) molecular markers were used to detect the variability among cultivars. Results showed that drought caused a significant reduction in growth, yield, and its attributes characters and chlorophyll content. Giza843 has a high yield, and its attributes characters under all watering treatments. At the same time, Sakha1 and Sakha4 showed increased sensitivity to drought conditions. Sakha4 gave high yield and its component under normal conditions while Giza716 cultivar showed high yield under severe conditions. The phenotypic coefficient of variation (PCV) value was higher than the genotypic coefficient of variation (GCV) value for all studied traits. One hundred seeds weight trait showed the highest PCV (71.15%), GCV (70.86%), and Genetic Advance (GA) (145.38), while the root length trait showed the lowest PCV (6.49%), GCV (6.04%), and GA (11.59). Higher values of heritability and GA were obtained for pods and leaves number/ plant, pods weight / plant, and 100 seeds weight. Results of tolerance indices indicated that Giza 716 and Giza843 cultivars (cv.) were drought-tolerant cultivars through they had the highest values of MP, GMP and YSI , the lowest values of TOL and values lower than unity of DSI. ISSR analysis identified 37 loci and heterozygosity ranged from 0.736 to 0.892 with an average of 0.827. Fourteen bands were polymorphic, with 37.83% percent of polymorphism. Polymorphism information con-tent (PIC) values were ranged from 0.75 to 0.89, averaging 0.84. Ten unique bands were used as molecular markers, most obtained by HB12 primer. ISSR markers' cluster analysis divided studied cultivars into three main clusters. Genetic similarity and dendrogram were in harmony with yield traits results