Genetic divergence studies in maintainer lines of rice (Oryza sativa L.) for yield and its attributing traits

Introduction

'Rice is Life' for billions of people, and rice production has influenced life style, diet, and economic status of humans across the globe. It is being cultivated in over 100 countries worldwide. Asia produces and consumes 90% of the world's rice. It is referred to as 'Global Grain'' and is the dominant staple cereal food of world (Bhargavi et al., 2023) [3] . The present rice varieties have reached the yield plateau to overcome this problem there is need to development of novel technology which meets the demand of the growing population by increasing the yield. The development of hybrid rice varieties using male sterility, maintainer lines and fertility restoration systems has been one of the turning moments in rice history which helps to meet the food security (Hyndhavi et al., 2025) [5] . Whereas "maintainer lines (B lines) are the key genotypes that are used to maintain the sterility and supply yield boosting genes to the female parent (A line) during new female line development in hybrid breeding. Maintainer lines (B lines) are mainly developed using B×B crossing method" (Hossain et al., 2020) [4] . The success of any breeding programme depends on the amount of variability present in the germplasm. The knowledge of genetic divergence is very important in the identification of suitable parents for hybridization. Wider the diversity among the parents, the greater will be the chance of obtaining heterotic combinations and broader would be the spectrum of variability in the segregating generations (Arunachalam., 1981) [2] .

This study estimates the nature and magnitude of genetic divergence in twenty-eight maintainer lines and two checks to maximize utilization of genetic resources and select suitable donor parents (Meena et al., 2017) [7] .

Materials and Methods

Materials and Planting

The experimental material for the present investigation comprised of 28 genotypes along with 2 checks. The experiment was done during Kharif season of 2024 in a randomized block design at the Institute of Rice Research, ARI, Rajendranagar, Hyderabad. All the genotypes were initially sown in a nursery bed. After twenty-five days after sowing, the seedlings were transplanted into the field with a spacing of 30 cm between the rows and 15 cm between the plants.

Data Collection

Observations were recorded randomly on five plants for days to 50% flowering, angle of the flower opening (°), stigma exertion (%), plant height (cm), panicle length (cm), number of productive tillers per plant, number of grains per panicle,1000grain weight, grain yield per plant. Data was recorded on quality parameters such as kernel length (mm), kernel breadth (mm), kernel L/B ratio, hulling (%), milling (%), head rice recovery (%) and amylose content (%) from genotype was recorded. Observations on hulling% and milling% were taken with the help of Satake Company make laboratory huller and polisher. Kernel length and kernel width of 10 hulled rice were measured by means of dial micrometer and length and breadth ratio was computed. Amylose content was estimated by chemical method. Statistical analysis was conducted using INDOSTAT software for the estimation of ANOVA. Genetic diversity was estimated by using Mahalanobis's D 2 (1936) [6] analysis to calculate the total genetic distance among the maintainer lines and the Tochers' method, as described by Rao was exercised to cluster the maintainer lines.

Results and Discussion

The results on genetic divergence of 30 rice genotypes for yield and yield components traits are presented and discussed here under.

Test with Wilk's criterion '˄'

Analysis of variance (ANOVA) for the different traits studied is presented in Table 2. The results revealed significant differences between the genotypes for all traits studied. [14] who also reported 'V' statistic to be highly significant with value of 2736.30 in their studies on 107 rice genotypes for yield and yield component traits, justifying the need to calculate D 2 values.

Grouping of genotypes into various clusters

The 30 genotypes of rice were grouped into eight clusters based on D 2 values using Torcher's method (Rao, 1952) [11] . The composition is presented in Table 3 [13] . (2022) [1] and Bhargavi et al. (2023) [3] .

Cluster means of the characters

The estimation of cluster means gives details on suitable donors for a specific trait. Mean performance of clusters for yield and yield parameters traits for the 30 rice genotypes were evaluated in the experiment and presented in [10] , Shanmugam et al.

(2023) [12] and Mondal et al. (2024) [8] .

Hence cluster V genotype BCN 2846 has good outcrossing traits with long slender grain intermediate range of amylose content and comparative yield per plant with checks (RNR 15048 and JGL 24423) which can be used as a parent in breeding programme for these traits and cluster IV genotype CMS 59B has shown medium slender grain type with low amylose content. BCN 2756 genotype of cluster III had shown short duration with moderate height but susceptible to blast and also showed less yield. While genotype of cluster II BCN 2950 showed higher yield and resistance blast. Therefore, it is necessary to carry out hybridization between the selected genotypes from divergent clusters to combine all the traits in to one hybrid.

Relative contribution of individual characters towards divergence

The relative contribution of various char acters towards divergence was reported to aid the breeder in the choice of parents for hybridization and effective selection. The 17 traits studied for genetic divergence have given ranks according to the contribution with respect to number of times appeared first are presented in the [15] and Nikhil et al. (2023) [9] .

Conclusion

According to the findings, considerable variation exists among the maintainer lines considered for the current study. The emergence of different yield attribute clusters implies the possibility of divergence among the lines used. Recombination breeding for Cluster II maintainer lines could increase the yield potential and had significant inter cluster distance. Clusters V had good outcrossing genotypes with long slender intermediate amylose content and IV has good quality trait maintainer lines and III had short duration maintainer lines with most significant inter-cluster distance. The maintainer lines in these clusters can be employed in crosses, which will be fruitful due to favourable recombination throughout the selection process.

Acknowledgement

AcknowledgementWe wholeheartedly acknowledge the support in terms of fund and guidance given by faculty at Institute of Rice Research and College of Agriculture, Rajendranagar, Hyderabad.

References

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