Eleven rice hybrids including two check varieties were evaluated to approximate their genetic variability, heritability and genetic advance for ten quantitative traits. The analysis of variance illustrated that all the quantitative traits differed significantly indicating that enough variation is presenting the studied materials. Among the desirable quantitative traits number of filled spikelet’s per panicle was found to have highest both phenotypic and genotypic variance followed by total number of spikelet’s per panicle. Almost all the characters showed a little variation between PCV and GCV revealing little influence of the environment on the expression of traits. High phenotypic and genotypic variance coupled with high heritability and high genetic advance was observed for number of filled spikelet’s per panicle, total number of spikelet’s per panicle, plant height and number of unfilled spikelet’s per panicle. Such findings stipulated that these traits were governed by additive gene actions which are fixable and these traits may be accounted for reliable index of selection. The genotypes G3 (IR79156A × EL108R) and G6 (IR79156A × EL253R) were selected as high response superior promising rice hybrids for achievable yield advantage 49% and 23%, respectively over best check varieties. Therefore, the G3 and G6 are proposed to be extensively evaluated for further trial of variety release. SAARC J. Agri., 18(2): 39-49 (2020)

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Phenotypic stability of 12 rice genotypes for plant height, days to maturity and yield were assessed at five different locations through regression and deviation from regression using Additive Main Effect and Multiplicative Interaction (AMMI) model. The result showed highly significant genotypic and G x E interaction. The G x E interaction influenced the relative ranking of the genotypes tested, BR1A/BR827R, Teea, BRRI dhan33 and Mayna showed low interaction effect with score nearest to zero with above average yield. While two genotypes BRRI hybrid dhan4 and Heera995 exhibited high positive interaction effect, gave mean grain yield around 5 ton/ha and was better suited to favorable environments. Similarly AMMI characterized the environments and identified Satkhira as a favorable environment for the better expression of the trait studied.

A study was conducted to assess the morpho-physiological divergence among 21 T. Aman rice cultivars at BRRI regional station, Sonagazi, Feni, during July 2008 to December 2008. Data were collected on 13 morphological and 14 physiological traits. Cluster analysis were carried out separately by using two softwares viz. GENSTAT v 5.5 and SPSS v 12.0 where in, both the software divided the cultivars into five clusters in both cases. The resulted clusters seemed to be very similar to some swapping genotypes which indicate that the softwares showed little dissimilarity. When clusterings were carried out using 13 morphological data, multivariate analysis showed five clusters in both GENSTAT and SPSS software with 19.05% swapping genotypes. When multivariate analyses were done with GENSTAT and SPSS softwares based on 14 physiological data, five clusters were also found with 14.29 % swapping genotypes. Of the two programs, GENSTAT appeared to be more reliable than the SPSS program. Inclusion of BR3, BR5, BR11, BR23, BRRI dhan33, BRRI dhan38, BRRI dhan44 and BRRI dhan46 giving emphasis on BRRI dhan33, BRRI dhan38, BRRI dhan44 and BRRI dhan46 is recommended for effective development of a breeding strategy in diallel fashion.

Twelve maintainer lines of rice were evaluated for 19 agronomic characters in a randomized complete block design to study the genetic divergence through multivariate analysis. Genotypes were grouped into three different clusters. Cluster I comprised maximum number of genotypes (ten) and II and III contain only single genotype each. PCA showed 70.29% variation against first three eigen values. The highest inter genotypic distance was observed between the genotype BRRI 1B and IR 73328B (2.278) followed by BRRI 3B and IR 68890B (2.229) and the lowest distance was observed (0.752) between genotypes BRRI 10B and IR 78355B followed by the distance (0.920) between genotypes BRRI 3B and IR 58025B. The inter cluster distance was larger than the intra cluster distances. The highest inter-cluster distance was observed between cluster II and III (7.113). The lowest inter-cluster distance was observed between cluster I and II (4.445) followed by cluster I and III (4.509). The inter cluster distances were higher than the intra cluster distances suggesting wider genetic diversity among the genotype of different groups. Among the characters anther length (0.00651), stigma length (0.00150), days to maturity (0.03018), number of tillers per hill (0.07890) and panicle weight (0.12713) were major characters that contribute to the genetic divergence.