Genetic Discrimination among Diverse Vicia faba L. Genotypes under Prevailing Environmental Stress Conditions of New Valley

Abstract

Faba bean (Vicia faba L.) is a major winter-sown legume crop, which is rich in protein and has considerable importance as food and fodder. Heat stress is one of the abiotic stresses that affect and reduce yield productivity of faba bean. This study aimed to evaluate seven divergent faba bean genotypes under terminal heat stress at New Valley and at Ashmoun as adequate environment during the winter growing season (2012/2013). To achieve this purpose; yield traits, stress tolerance indices, biochemical markers of proteins and isozymes, molecular markers based on ISSR-PCR and IRAP-PCR techniques as well as cluster analysis were used. For seed yield/plant (g), Sakha-4 is the most tolerant genotype, that it was adaptable for the prevailing condition of New Valley and gave the highest level of yielding capacity. Otherwise, Nubaria-2 is the least tolerant one, which ranked last genotype under non-stress conditions as well as under stress conditions. This confirmed by detecting some stress tolerance indices that are appropriates in selection of tolerant genotypes. Regarding the protein banding profiles, all genotypes tested showed substantial differences, where new protein bands appeared and others disappeared in the protein patterns of genotypes grown under contrasting conditions. The results also stated that, heat stress effects indicated the interaction between heat stress and the ability of plant genetic complement for inducing or inhibiting the encoding genes to produce some defensive proteins against the stress. Else, four isozymes gave some biochemical markers which could be considered as biochemical markers for heat stress tolerance as well as biochemical fingerprints for tested genotypes. A total number of 85 amplified fragments (AF) were generated by the ten ISSR-PCR primers with 88.2% polymorphism. The size of the amplified fragments ranged from 1447 bp (AF06) to 135 bp (AF16). A total of 26 specific markers including either the presence (M+) or absence (M-) were identified out of the total amplified fragments in the tested genotypes, and they could be considered as marker assisted selection (MAS) for heat stress tolerance and as molecular fingerprints for tested genotypes. Values of polymorphic information content (PIC) and discriminating power (D) indicated that primer HB-14 was the most efficient to analyze genetic variability among faba bean genotypes with values of 0.99 and 0.889, respectively, followed by primers 17898B and HB-10. A whole of 141 AF were generated via the ten IRAP-PCR primers with 87.3% polymorphism. A total of 60 specific markers including either the presence (M+) or absence (M-) were identified among the ten primers; such bands could be considered as molecular markers (marker assisted selection) for heat stress tolerance as well as molecular fingerprints for the tested genotypes. Values of PIC and D indicated that primer 4376 was the most efficient to analyze genetic variability with values of 0.988 and 0.935, respectively, followed by primers 4314 and 4374. UPGMA cluster analysis of the seven genotypes tested based on the ISSR-PCR and IRAP-PCR data revealed that, Nubaria-2 genotype represented as a separate phenetic line which had the lowest similarity values with all other genotypes. The other genotypes were classified into two main clusters. The first cluster included three genotypes (L3, NBL-5 and NBL-Mar.3); the second cluster included three genotypes also (Sakha-4, Misr-3 and Misr-1). Keywords: Faba bean, heat stress, yield, stress tolerance indices, biochemical markers, molecular markers, PIC, D, cluster analysis.