Abstract
Variability Assessment and Genotype-environment Interaction of Groundnut (Arachis hypogaea L.) Under Saline Stress
The study was undertaken during 2010 to 2013 at Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh to study the variability assessment and genotype- environment interaction of groundnut (Arachis hypogaea L.) under saline stress. Four experiments were performed at BINA glass house condition for this study. First experiment was conducted to standardize the protocol for screening and study the mechanism of salinity tolerance in groundnut with three varieties, six levels of salinity and salinity imposed at four growth stages. Based on relative performance of yield contributing characters, biochemical aspects and nutrient contents of leaves and stem, Binachinabadam-3 emerged to be a tolerant variety and based on root shoot characters, Dacca-1 appeared as tolerant while Zhingabadam always performed as sensitive variety. Salinity treatments had most adverse effects at flowering stage, followed the trend of sensitivity- flowering stage > vegetative stage> pre sowing stage > pod filling stage. All varieties were found to be tolerant up to 7.5 dS/m. Salt tolerance mechanism is related to Na+, K+, Ca+, chlorophyll and proline content of plant tissue. Binachinabadam-3 (tolerant) contained highest amount of K+, chlorophyll and proline content and Zhingabadam (sensitive) contained highest amount of Na+, Cat. The stem tissues contain more nutrients (Na+, K+, and Ca+) than leaf tissue of groundnut. Second experiment was conducted to screen groundnut genotypes under salinity stress. Fifty one lines/varieties were assessed under 8 dS /m salinity and imposed at flowering stage. Based on the performance of pod numbers, pod yield, root weight and shoot weight per genotype, 5, 12, 13 and 21 genotypes were identified as tolerant, moderately tolerant, moderately sensitive and sensitive, respectively. Out of them, 5 tolerant, 5 moderately tolerant, 5 moderately sensitive and 7 sensitive lines/variety selected for next experiments. In third experiment, twenty two genotypes of groundnut were used for molecular analysis to examine the variability of groundnut using SSR markers. Five markers yielded a total of 21 alleles, which ranges from 3 to 5 per locus with an average number of 4.2 alleles. Genetic distance (GD) between the genotypes ranged from 0.00 to 0.9003. The common allele frequency at each locus ranged from 59.09% in PM3 and PM36 to 36.36% in PM32. The polymorphic Information Content (PIC) values ranged from 0.5076 (PM15) to 0.6964 (PM32) and average 0.5754. Cluster analysis using the Unweighted Pair Group Method with Arithmetic Means (UPGMA) classified 22 groundnut genotypes in two major clusters, Cluster I comprised of 8 genotypes. Cluster II comprised of two sub clusters, sub cluster one comprised of 3 genotypes. One the other hand, sub cluster two produced two sub-sub clusters. Sub sub Cluster II.II.I comprised of 7 genotypes and sub sub Cluster two comprised of 4 genotypes. Pooled analysis of genotype environment interaction showed significant variation among the genotypes and environments for studied parameters. Both the environment (linear) and genotype x environment (linear) components of variation for stability were also significant. Binachinabadam-3 and C-32 appeared to be stable for most of the studied parameters. In conclusion, the salt tolerant variety has higher amount of K+, chlorophyll and proline accumulation which played a defensive role against salt stress. The variation among genotypes assessed by molecular markers could be used in future breeding program for development of salt tolerant groundnut variety. The genotype C-32 has been found to be the most stable with reasonable yield potential and deserves further evaluation in saline area of Bangladesh for its release as a salt tolerant variety.