Abstract
Five experiments were conducted during April 2005 to June 2007 in glass house conditions. The range of temperature and relative humidity were about 20-35 °C and 60%-95%, respectively. These experiments were conducted to standardize protocols for screening salinity tolerant genotypes of groundnut (Arachis hypogaea L.) and to study the genetics of the traits attributing salinity tolerance. All the experiments were carried out in polyethylene lined earthen pots of size 27cm x 22 cm, filled with sandy loam soil and rotten cow dung in 1:1 ratio. Recommended doses of fertilizer, pesticides and intercultural operations were followed. The protocol was standardized with three varieties of groundnut, five levels of salinity including one control and three growth stages. Flowering stage showed to be the most sensitive of all stages, salinity levels from 7 to 8 dS/m and shoot biomass appeared to be most appropriate for screening. Based on these findings, 50 mutants/varieties were assessed under 8dS/m salinity stress; 3, 15 and 22 mutants/varieties were identified as tolerant, moderately tolerant, and moderately sensitive, respectively. Further screening of 2 tolerant, 8 moderately tolerant and 12 moderately sensitive mutants/varieties based on pod number identified 2 mutants/varieties as tolerant, 7 as moderately tolerant and the remainders as sensitive. In contrast, screening based on pod yield identified two mutants/varieties as tolerant, 3 as moderately tolerant and the remainders as moderately sensitive or sensitive. To study the genetics of shoot biomass and some related traits under salinity stress, 2 moderately tolerant and 4 moderately sensitive mutants/varieties were crossed in all possible combinations without reciprocals and genetics was studied in F2. In contrast, for genetic studies of pod yield and some related traits 1 tolerant, 3 moderately tolerant and 2 sensitive mutants/varieties based on pod number was crossed following the same design and the genetics was studied in F1 .It was revealed that non-additive gene action was more important than additive gene action in the expression of shoot biomass, leaf biomass, pod number and yield under salinity stress. Wr-Vr analysis showed absence of non-allelic interaction for the expression of shoot and total biomass, and pod number. In contrast, pod yield showed presence of epistasis. All the traits, in both genetic studies appeared to be controlled by 2 to 5 genes and also the genes with positive and negative effects were asymmetrically distributed amongst the parents. Pod number showed the highest narrow sense heritability while leaf biomass and pod yield showed moderate heritability. This suggests simple progeny selection with pod number could be effectively followed for future varietal development program for salt tolerance in advancing the segregating materials. Moreover, selection based on leaf biomass and pod yield could also be practiced giving more importance on pod number.