Genetic Divergence Studies in Subspecies of Oryza sativa L.

Abstract

An experiment was carried out to study the divergence among twenty four rice genotypes (14 indica and 10 japonica lines) for 15 agro-morphological traits using D 2 statistics and at molecular level using 114SSR markers. The cluster analysis using Mahalonobis' D 2 statistics classified the genotypes into five clusters. The cluster IV was the largest with seven indica and three tropical japonica types. The second largest cluster (V) accommodated four tropical japonica and two indica genotypes. The intra cluster distance ranged from 1.077 to 8.299 and it showed a gradual increase from cluster I to cluster V. Cluster III with four genotypes showed the highest inter cluster distance with cluster I (14.312), followed by cluster II (12.032) and cluster IV (11.734). Cluster II with AC 38479 and IR 64 showed the highest mean values for five traits viz., panicle length, number of primary branches panicle -1 , number of secondary branches panicle -1 , filled grains panicle -1 and single plant yield and the lowest mean values for hundred grain weight, kernel length, kernel breadth and kernel thickness which are desirable. The kernel traits viz., kernel L/B ratio (35.14%), 100 grain weight (25.73%), kernel thickness (14.13%) and kernel breadth (12.31%) alone contributed for 87.31% of the total genetic divergence. In molecular diversity analysis, 69 SSR markers were detected to be polymorphic out of 114 markers. In total, 216 alleles were detected and the number of alleles amplified ranged between two to seven. The average number of alleles obtained was 3.13. The Polymorphism Information Content (PIC) which reflects the allelic diversity varied from 0.08 (RM2) to 0.81(RM3317) and its average was 0.5. The dendrogram based on the UPGMA classified the 24 genotypes into four major distinguishable clusters with two sub clusters for cluster I. The Jaccard's dissimilarity index was lowest (0.34) between CB 16144 and CB 15138; highest (0.89) between CB 16174 and Pato as well as between CB 16174 and AC 38476. It is concluded that in both methods, some distinct genotypes in each group were accommodated in the same cluster without separation. Also, no distinct clusters were formed for each of the two sub groups indica and tropical japonica separately but the genotypes of both the groups were spread over all clusters indicating sufficient genetic diversity within the groups which can be utilized in selecting parents for hybridization program.

Assessment of Morphometric Diversity for Yield and Yield Attributing Traits in Rice (Oryza sativa L.) for Tolerance to Heat Stress

“…Analysis of variance for the experiment involving a set of 200 germplasm lines of rice for all the characters revealed highly significant differences among the genotypes for all the characters indicating sufficient variability existed in the present material selected for the study and indicating the scope for selection of suitable initial breeding material for crop improvement. Similar results were also reported by [5]. Based on D 2 values, the genotypes were grouped into fifteen clusters using Tocher's method.…”

Molecular Marker and Test Cross Information Aid Selective Advancement of F4 Generation of CB174R/Azucena: An inter Sub-specific Cross in Rice for Restorer Development

“…It is important that the parents chosen should have adequate genetic diversity to isolate desirable recombinants with fertility restoration ability. Accordingly, both the parents chosen for our crossing programme namely CB 174R and Azucena are genetically diverse and fell in different clusters for both agronomic traits and using simple sequence repeat markers [14].…”

“…During the course of line development, it is a practice in hybrid programs to advance superior plants with fertility restoration ability at later generations. Both the parents used in the present study possess the fertility restorer genes Rf3 and Rf4 for Wildabortive cytoplasm screened in an earlier study [15].…”