Abstract
Seven experiments were carried out at the Experimental Farm of Regional Agricultural Research Station, BARI, Rahmatpur, Barisal during 2004-05 to 2007-08 crop seasons for screening and genetic analysis of salt tolerance in wheat. The experiments included salinity sensitivity test, salinity screening and validity test, genotype x environment interaction and genetic diversity under saline and non-saline environments, growth and yield response of selected genotypes to salinity at different growth stages and genetic analysis for salt tolerance. The results of salinity sensitivity of 45 genotypes demonstrated that germination, root and shoot length were markedly reduced at NaCl salinity level above 12 dS/m. Based on relative total dry matter, the results of two trials on screening of 45 genotypes in two seasons against NaCl salinity showed five and seven genotypes to be tolerant with common of five genotypes during 2004-05 and 2005-06, respectively. On the other hand, six and three genotypes with common of three exhibited tolerant during 2004-05 and 2005-06, respectively on visual scoring. Validity test of the selected genotypes appeared that the distribution pattern of the genotypes tested into various salinity tolerance groups remained fairly consistent. Stability analysis after Eberhart and Russell's model showed significant variation due to the genotypes and the environments for yield and its component parameters. Both the environment (linear) and genotype x environment (linear) components of variation for stability were also significant. The genotype G11 appeared most stable for number of spikes per plant and grain weight and G11, G22 and G37 were the most stable and desirable genotypes with good yield. Study of genetic divergence provided for the genotypes to be grouped into five clusters in both environments. Number of genotypes in each cluster varied with salinity environments. Twelve genotypes in the cluster V under non-saline and five genotypes under saline environment in the cluster IV had good performance. There are wide distance between cluster III and IV, between I and V, and between II and V in non saline. Again, under saline environment, wide distance was found between cluster III and IV, between I and V, between I and II, and between IV and V. Growth and yield response of genotypes to salinity level and salinity treat on growth stages exhibited highly significant variation for yield and its components. Grain yields greatly decreased with increase in salinity and the magnitude differed depending upon the tolerance of genotype. The yield reduction in G33, a tolerant genotype was 25 % at 16 dS/m while it was 51% in G45, a susceptible genotype. NaCl salinity treatments were of most adverse effects on vegetative and heading stages than on grain-filling stage. Combining ability analysis revealed significant GCA and SCA for all the salinity traits indicating additive and non-additive gene actions in the inheritance of these salinity traits. GCA: SCA ratios suggested preponderance of non-additive gene action in the genetic system controlling salinity characters. No single parent contained all the desirable traits. P45 and P33 appeared to be the best general combiners for salt tolerance traits. The cross P1 X P15, P11 XP15 and P15 X P22 were found to be the best specific combiners for the traits. The best cross-involving poor x poor general combiners indicated over dominance and transgressive segregation for salt resistance. Vr-Wr analysis also showed over dominant type of gene action in the inheritance of salt tolerance trait.