SCREENING OF RICE (Oryza sativa L.) GENOTYPES FOR DROUGHT TOLERANCE UNDER RAINFED FIELD CONDITION

Abstract

An investigation was carried out with 24 rice genotypes composed of land races and cultivars to identify drought tolerant genotypes under rainfed field condition. The experiment was conducted at Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh during rabi season of 2016-17 using randomized complete block (RCB) design with three replications under control and rainfed drought blocks. The results of the analysis of variance revealed significant differences among the genotypes and treatments for all the characters studied viz. days to 50% flowering, plant height, number of tiller per hill, proline content, chlorophyll content, shoot fresh weight, shoot dry weight, root fresh weight, root dry weight, root length, root volume, number of grain per plant, 1000-grain weight and yield per plant. The genotype x treatment interaction was significant for most of the characters except root dry weight, root length, root volume and 1000-grain weigh. Comparing the mean values, control blocks appeared superior performances than drought blocks in most of traits except proline content and days to 50% flowering. Phenotypic coefficient of variation was higher than the genotypic coefficients of variation indicating environmental influence on the traits. High heritability coupled with high to moderate genetic advance as per cent of mean was observed for all the traits except days to 50% flowering. These characters can be further used for selection of superior genotypes. In this study, the inter-relationship between grain yield and its contributing traits were determined by correlation matrix. The result ofthe correlation co-efficient among measured traits under control and drought stress conditions showed that grain yield per planthad a significantly positive correlation with shoot dry weight and number of grains per plant. Positive direct effect revealed for grain yield per plant via 1000 grains weight, number of grains per plant, root dry weight, shoot dry weight.Therefore, these traits can be used as anindicator for breeding of grain yield under drought stress conditions. Based on the genetic distance all the 24 genotypes were grouped under three different clusters. The mode of distribution of genotypes from different eco-regions into various clusters was at random indicating that genetic diversity was not related. In both control and drought stress conditions, cluster II contained some common genotypes viz. G9 and G10 with the highest number of relative mean for number of tillers per hill, chlorophyll content, shoot fresh weight, shoot dry weight, root fresh weight and yield per plant. The results of the principal component analysis (PCA) showed that the first six principal component axesexplained variations of 82.34% in control condition and 84.34% in drought conditions of the total variations in the experimental rice populations. Considering overall PCA, the highest genetic diversity was contributed by PC1 and PC2 in both control and drought conditions for shoot dry weight, root dry weight, root volume, number of grain per plant and yield per plant. Therefore, these characters should be given emphasisfor further selections in breeding.Again, the present investigation also indicated. Again, the results of drought susceptibility indices (DSI) indicated the superiority in the G23 closely followed by the genotypes G24, G15, G22, G9, G3, G21, G10, G13, G6, G16, G19 and G12. Due to overall superior performances genotypes BRRI dhan71 (G24), BRRI dhan57 (G22), BRRI dhan56 (G21), Kalamanik (G9) and Burikatari (G10) might be useful for future drought tolerance breeding as a novel sources of drought tolerant genes and genotypes and Kalamanik (G9) and Burikatari (G10) might be taken under further evaluation to release as drought tolerant variety.