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Genetic diversity studies in kodo millet ( Paspalum scrobiculatum L . )

The present investigation was undertaken to assess genetic diversity in seventy genotypes of kodo millet. The analysis of variance revealed the presence of significant variation among the genotypes for all 13 characters. Higher genotypic coefficient of variation (GCV), phenotypic coefficient of variation (PCV), heritability and genetic advance as per cent mean were recorded for thumb raceme length, number of productive tillers per plant, length of panicle, raceme length and grain yield per plant, indicating that simple selection could be practised for improving these traits. Seventy genotypes were grouped into seven different clusters on the basis of magnitude of D2 values by Mahalanobis D2 analysis. Cluster I had 51 genotypes followed by cluster II with 14 genotypes, while clusters III, IV, V, VI and VII were mono genotypic. The inter–cluster distance was high between clusters II and III and therefore it is suggested to use these genotypes as parents for hybridization to evolve potential segregants.


INTRODUCTION
Millets are a group of highly variable small-seeded grasses, widely grown around the world as grains for food and fodder. They are highly tolerant to extreme weather conditions and the nutrient contents are similar or higher than other major cereals. Kodo millet is one of the most important small millets grown in large areas of developing world especially in Africa and Asia. Kodo millet, Paspalum scrobiculatum L. is a self pollinated crop belonging to the Poaceae family, is a tetraploid (2n=4x=40) good source of minerals. Knowledge of genetic variability in respect of yield in any species is a very valuable estimation in plant breeding programme, since it helps in selection of ideal parents and or traits for selective hybridization. People have come across the importance of kodo millet and hence its demand is increasing. To fulfill the demand of kodo millet in future, extensive research is needed (Nirubana et al., 2017). Therefore, the present study is conducted to analyse the genetic variability and diversity among 70 genotypes of Kodo millet.

MATERIALS AND METHODS
The present investigation was carried out at Educational and Research Farm, Department of Agricultural Botany, College of Agriculture, Dapoli, Dist. Ratnagiri, Maharashtra during kharif, 2020-21. The material comprised of 70 genotypes of Kodo millet collected from ICAR-Indian Institute of Millets Research, Rajendranagar, Hyderabad ( Table 1). The experiment was conducted in Randomized Block Design with two replications. The seed was dibbled at a 30 cm distance between row to row and 20 cm distance plant to plant. Each plot had a 2.0 m × 0.9 m area, with three rows per genotype. Each row had 10 plants thus constituting 60 plants in two replications. A. standard package of practices was carried out to maintain a good crop stand. The observations were recorded on five plants selected randomly from each genotype for thirteen quantitative characters and two qualitative characters i.e. culm branching and panicle appearance (Bowen, 2009). The average values were used for further analysis. The analysis of variance was computed as suggested by Panse and Sukhatme, (1985). The phenotypic and genotypic coefficients of variation (PCV, GCV) were computed as per Burton and DeVane (1953). Heritability in a broad sense (H 2 ) was estimated by formulae suggested by Lush (1949) and the genetic advance was calculated in percent by the formula suggested by Johnson et al. (1955). Genetic diversity was estimated by Mahalanobis (1936) D 2 statistic technique as described by Rao (1952). The statistical package used for analysis was GENALEX. Protein and calcium content was estimated as per the standard procedure and expressed as per cent.

RESULTS AND DISCUSSION
Analysis of variance revealed significant differences among the genotypes for all the 13 quantitative characters indicating the presence of considerable genetic variation in the experimental material ( The phenotypic coefficient of variability was greater than the corresponding genotypic coefficient of variability. The genotypic coefficient of variation helps in assessing the genetic reliability of the different characters and enables to compare the magnitude of variation. The genotypes were highly variable for characters thumb raceme length (37.5%), the number of productive tillers per plant (27.7%), length of panicle (23.37%), grain yield per plant (23.10%), straw yield per plant (21.48%) and raceme length (21.40%) as indicated by the estimates of PCV (>20%). (Table 4). These results are in agreement with Brunda et al. (2014) for grain yield per plant, Nirubana et al. (2017) for the number of productive tillers per plant and Sao et al. (2017) for the length of panicle.
Among the traits, the highest value of GCV was registered for thumb raceme length (35.61%), number of productive tillers per plant (26.58%), length of panicle (22.79%) and grain yield per plant (20.47%) suggesting that these characters are under the influence of genetic control ( Table 4). These results are in accordance with Keerthana et al. (2019).
The estimate of genetic advance as per cent of mean ranged from 6.95 (days to maturity) to 69.66 per cent (thumb raceme length). Thumb raceme length (69.66%), the number of productive tillers per plant (52.55%), length of panicle (45.8%), grain yield per plant (37.36%), raceme length (37.04%), plant height (36.73) and straw yield per plant (31.01%), showed higher GAM, indicated that top priority should be given for these characters while formulating selection strategies (       genotype which had better mean value for the characters days to first flowering and days to maturity ( Table 7). Among the 13 characters studied the character grain yield per plant (22.65%) contributed the highest for divergence followed by harvest index (14.43%), straw yield per plant (12.43%) and thumb raceme length (12.01%). However, the character number of productive tillers per plant (5%), length of panicle (5%), raceme number (5%), days to first flowering (3.44%) and plant height (3%) recorded the lowest contribution (Table 7). Thippeswamy et al. (2018) found similar results for plant height, Jyoti et al. (2020) for the number of productive tillers per plant.
From the present investigation, it is evident that a wide range of variability is present for different traits coupled with high heritability and high genetic advance as percentage of t h e mean for important yield traits like thumb raceme length, the number of productive tillers per plant, length of panicle and raceme length; hence selections based on these traits could improve productivity in kodo millet. While, clusters II and III were most diverse to each other, hence genotypes present in these clusters are suggested to provide a broad-spectrum variability in the evolution of segregating generation.