Genetic divergence analysis
The study of genetic divergence among 113 rice genotypes including checks were grouped in to eleven different non-overlapping clusters as presented in Table 1 according to non-hierarchical euclidean cluster analysis by following
Beale 1969,
Spark 1973 and by tocher method. Cluster II, having 20 genotypes, emerged with highest number of entries followed by cluster III with 15 genotypes, cluster VI and cluster XI with 12 genotypes, cluster I and cluster IX with 10 genotype, cluster V and VIII with 8 genotypes, cluster IV and VII with 7 genotypes and cluster X with only 4 genotypes.
Cheema et al., (2004) advocated that the number of clusters formed, number of genotypes in the clusters and superposition of the genotypes within the clusters indicated the possibility of genetic improvement for yield and yield components.
The estimates of intra and inter-cluster distances for eleven clusters are presented in Table 2 according to non-hierarchical euclidean cluster analysis by following
Beale 1969, Spark 1973 and clustering and their interrelationships by Mahalnobis euclidean distance. The highest intra-cluster distance was found for cluster X (23.302) followed by cluster II (22.604), cluster I (22.451), cluster VII (19.536), cluster III (18.657), cluster VI (16.431), cluster VIII (16.016), cluster IX (15.933), cluster V (11.787), cluster XI (9.124) and cluster IV (7.859). The maximum inter-cluster distance was recorded between cluster VII and XI (82.207) followed by cluster I and VII (71.065), cluster VII and X (63.163), cluster VI and XI (61.996), cluster VII and VIII (58.872), cluster VII and IX (58.307), cluster III and VII (54.139), cluster IV and VII (52.302), cluster V and XI (50.554), cluster II and XI (46.673), cluster II and VII (46.384), cluster V and X (46.151), cluster I and XI (44.385), cluster VI and X (44.182), cluster IV and X (43.425), cluster I and VIII (42.845), cluster I and X (41.655), cluster II and X (40.129) and cluster VI and VII (40.023). The discrimination of germplasm lines into so many discrete clusters indicating presence of high degree of genetic diversity in the evaluated materials. Earlier workers have also reported substantial genetic divergence in the rice materials
(Nayak et al., 2004; Suman et al., 2005; Gahalain, 2006; Chandra et al., 2007; Singh et al., 2008; Dushyantha and Kantti 2010; Seetharaman et al., 2013; Supriya et al., 2017; Sarif et al., 2020).
The highest intra-cluster distance was found for cluster X (23.302) has symmetrical genetic dissimilarity matrix depicting pairwise comparisons between the tested genotypes indicates closer genetic similarity within USAR 1, NDRK 5049 NDRK 50056 and Pokkali, suggesting their common origin and geographical occurrence (Table 3). Moreover, the maximum inter-cluster distance was recorded between cluster VII (NDRK 5007, NDRK 5014, NDRK 50033, NDRK 5011, IR 85920-11-2-1AJAY1-2-B, Kalanamak 3, Sundari) and XI (NDRK 5062, NDRK 5099, NDR 2064, NDRK 5038, NDRK 5047, NDRK 5042, CSR 28, Pusa Basmati 1, Moti Gold, IR 11 T 183, CSR 43, Sarjoo 52). These genetically highly dissimilar genotypes belonged to different climatic situations and may act as prospective parents for transgressive breeding and exploitation of heterosis in hybrid breeding programs.
The intra-cluster group means for sixteen characters (Table 3) revealed marked differences between the clusters in respects of cluster means for different characters. The highest cluster mean for grain yield per plant was observed in cluster III (21.634 g) followed by cluster II (19.247 g), cluster VII (19.062 g) and cluster V (19.033 g), while XI possessed low cluster mean for grain yield per plant
i.
e., 10.484 g.
Presence of substantial genetic diversity among the germplasm lines screened in the present study indicated that this material may serve as good source for selecting the cluster VII (NDRK 5007, NDRK 5014, NDRK 50033, NDRK 5011, IR 85920-11-2-1AJAY1-2-B, Kalanamak 3, Sundari) and XI (NDRK 5062, NDRK 5099, NDR 2064, NDRK 5038, NDRK 5047, NDRK 5042, CSR 28, Pusa Basmati 1, Moti Gold, IR 11 T 183, CSR 43, Sarjoo 52) diverse parents for hybridization programme aimed at isolating desirable segregants for grain yield and other important characters.
The choice of suitable diverse parents based on genetic divergence analysis would be more fruitful than the choice made on the basis of geographical distances. This finding is in conformity with the previous reports advocating lack of parallelism between genetic and geographic diversity in rice
(Nayak et al., 2004; Suman et al., 2005; Gahalain, 2006; Chandra et al., 2007; Singh et al., 2008; Dushyantha and Kantti 2010; Seetharaman et al., 2013; Supriya et al., 2017; Sarif et al., 2020).
Contribution of sixteen traits of rice toward divergence
The contribution of sixteen characters towards divergence in Table 4 showed the highest contribution by spikelets per panicle (55.31%) followed by grains per panicle (23.10%), while the grain yield per plant (0.00%) showed lowest contribution towards divergence.