Assessment of genetic variability for yield and yield contributing traits in rice (Oryza sativa L.) using Mahalanobis D2 analysis

Introduction

Rice is the most important grain crop in the world. The world wide diffusion has established this crop as the most important human food. Farmers have fed rice more than any other important cereal crop like wheat, barley and maize. Near about 40% world's human population rice is the most important staple food, especially in East Asia, South East Asia, South Asia, the Middle East and the West Indies. In Chhattisgarh rice occupies average of 3.6 million hectare with the productivity of the state ranging between 1.2 to 1.6 tonnes/hectares depending upon the rainfall. National wise Chhattisgarh stood 7 th rank in production. The unabated growth of rice consumers, breeders have manipulated the rice phenotype for higher grain yield by accessing the rich diversity. Yield apart, the diversity has also assured the climate resiliency of the crop in the years to come. There is a need to changes to be made in phenotype for its progression with the intent for revision of genetic yield ceiling is evident in compare assessment of rice cultivars used by the farmers such as traditional, semi dwarf, hybrid, new plant type and super-rice.

Genetic Divergence Analysis

Analysis of genetic diversity existing within and between groups of germplasm is important and useful in making proper choice of parents for higher heterosis and useful recombinants. The quantitative assessment of genetic divergence was made by adopting Mahalanobis D 2 statistics for yield and its contributing characters. D 2 statistics, a concept developed by Mahalanobis (1936), is an important tool for plant breeders to classify the genotypes into different groups based on genetic divergence between them.

Materials and Methods

The experimental materials comprised 50 rice genotypes including two checks namely Purnima and Danteshwari. The experimental materials were received from germplasm section, Department of Genetics and Plant Breeding, College of Agriculture, Indira Gandhi Krishi Vishwavidyalay, Raipur (C.G). These genotypes were evaluated in Randomized Block Design with 2 replications during Kharif 2023. Observations were recorded on 3 plants from each replication.

Results and Discussion

The highest mean performance was observed for plant height 157.44 cm, while high PCV% and GCV% were observed for harvest index (%) and grain yield per plant whereas biological yield per plant, grain length breadth ratio, number of tillers per plant and plant height (cm) expressed moderate type PCV% and GCV% (Table 1). High heritability were observed for all the characters under study except panicle length (cm), 100 grain weight(g) and grain length (mm). The high heritability estimate shows that all the traits under study except (panicle length, 100 grain weight and grain length) reflects that all these traits are governed by additive gene action and hence the phenotypic selection would be effective for improving the overall mean for these characters The character which have high genetic advance as% of mean coupled with high heritability estimates such as days to 50% flowering, plant height (cm), number of tillers per plant, grain length breadth ratio, biological yield per plant harvest index (%) and grain yield per plant suggested that genotypic variation in the present material for these character may possibly due to high additive genetic variance and hence selection for these characters must be effective for bringing improvement. Similar results were reported by Kujur et al. (2023) for grain yield per plant, biological yield per plant and number of tillers per plant. Sao et al. (2024) for grain yield per plant, 1000 grain weight (g), plant height (cm) and days to 50% flowering. For genetic divergence cluster analysis was performed by D 2 clustering analysis method using Euclidean distance as dissimilarity measure which divided 52 genotypes into eight clusters in table 2. respectively. The cluster I constituted of 38 genotypes, forming the largest cluster followed by cluster II (5 genotypes), cluster III IV and V (2 genotypes) and cluster VI VII and VIII (1 genotypes). The pattern of group constellation proved the existence of significant amount of genetic divergence and variability among the genotypes. Inter-cluster distance were calculated among the eight clusters of each yield characters and presented in table 3. presented below respectively. Among the yield traits maximum inter-cluster distance was present between cluster IV and VI (863.27) followed by between cluster IV and VIII (811.98) followed by between cluster III and VII (506.69) followed by VII and VIII (351.70).Minimum inter cluster distance was present between cluster I and II (105.32) followed by cluster I and IV (1.8.39). in governing expression of these traits. Selection for further improvement these traits would be rewarding.  Cluster I constituted of 38 genotypes, forming the largest cluster followed by cluster II (5 genotypes), cluster III IV V (2 genotypes) and cluster VI VII VIII (1 genotypes). The pattern of group constellation proved the existence of significant amount of variability.  Cluster IV and VI had a largest inter-cluster distance among yield attributing characters respectively, which indicates that they were highly divergent populations. Hence, crossing between genotypes belonging to these clusters may result in high heterosis, which could be exploited in crop improvement.

Acknowledgement

AcknowledgementThe authors are thankful to the Department of Genetics and Plant Breeding, College of Agriculture, Indira Gandhi

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