Characterization of genetic diversity in forage sorghum (Sorghum bicolor L. Moench) for fodder improvement

Introduction

Sorghum is the best crop for semi-arid tropical regions, fits in well with sustainable agricultural models, and is a staple food for the world's poorest and most food insecure population. The cultivation and use of sorghum are prevalent worldwide; an estimated 42 million hectares of sorghum harvesting land are used worldwide. Although there is a growing global demand for sorghum production, India's production is failing to keep pace with the demand. In terms of both acreage and output, sorghum ranks fifth globally among cereal crops, after rice, wheat, maize, and barley. Sorghum is grown over an area of 39.7 m.ha. and produces around 63.5 m.t. worldwide in roughly 105 countries. Of the world's sorghum production, half is produced in Africa (50.2%), followed by the America (32.4%) and Asia (13.4%). In India, its cultivation encompasses an area of around 4.0 million hectares for food, feed, and fodder purposes, producing 4.6 million tons of grain annually (FAO, 2024) [7] . Sorghum [Sorghum bicolor (L.) Moench], 2n = 2x = 20, is a C 4 plant belonging to the Poaceae family that is widely used for food, feed, and fodder. In India, it is cultivated over an area of around 4.24 million hectares for food, feed, and fodder purposes, yielding 4.78 million tons of grain annually. The world's greatest population of cattle is found in India, an agricultural nation. The availability of green feed is crucial for the security of animals. In India, pastures make up just 3.4% of the total land area, and cattle are typically kept on subpar pasture grasses or are stall-fed, mostly agricultural waste. India already lacks enough dry fodder (22%), green fodder (62%), and concentrates (64%). Given that sorghum is still regarded as a crop for marginal environments, a number of crop improvement initiatives were created to optimize biomass output as a result of its many applications as fodder (Prasanth et al., 2021) [17] . According to the 21 st livestock census (2024), India is home to 20% of the world's livestock population in just 2.4% of the country's total land area (68.0 million in Uttar Pradesh), meaning that these shortages will only become worse (BAHS, 2024). The main reason for low productivity and output of fodder is that farmers do not have access to better forage crop types with high-quality fodder. A supply of nutrient-rich fodder is essential to the success of any dairy enterprise. Compared to other kharif and summer season fodder crops, forage sorghum is a more palatable, nutrientdense feed with excellent dry matter yield and digestibility. India's sorghum output is inadequate despite the growing global demand for the crop. There are several reasons why sorghum isn't more widely used. The most notable and significant factor is the dearth of adequate sorghum varieties. Breeders work to create new cultivars that are extremely effective and adaptable to all types of environments. The ideal variety is one that can thrive in a variety of growing environments within a certain producing region. In other words, as production circumstances improve, the cultivars must be able to withstand a variety of stressors and perform well in terms of yield (Erdurmus et al., 2021) [6] . The degree of variation between or within species is referred to as genetic diversity. The necessity of optimal parental variety in order to produce superior genotypes in the segregating generations has been underlined by a number of researchers. A potential and ongoing source for creating new and improved crop varieties is the genetic heterogeneity of both cultivated species and their wild relatives. In order to evaluate this level of diversity, group distance based on numerous characters was calculated using D 2 statistics. It is now one of the key methods for evaluating genetic divergence based on a variety of phenotypes. The use of these methods for evaluating genetic diversity in plant breeding was proposed by Rao (1952) [19] . Genetic divergence has been highlighted as being crucial for increasing yield potential through hybridization. In addition to serving as a limiting factor for assessing the level of divergence across various populations, Mahalanobis generalized distance (D 2 ) is also useful for choosing genetically diverse parents for a successful breeding program. Considering all these aspects, a research study was carried out to analyse genetic diversity in sorghum.

Materials and Methods

The current study, "D 2 analysis in forage sorghum (Sorghum bicolor L. Moench)," was carried out during the kharif season at the Sardar Vallabhbhai Patel University of Agriculture & Technology Crop Research Centre in Meerut. The Crop Research Center is located in the North Western Plain Zone, at an elevation of roughly 297 meters above mean sea level with 29º01'N latitude and 77º45'E longitude. The experimental material included thirty-seven different forage sorghum genotypes. Table 1 provides information about the experimental material. The experiment was set up using a randomized block design with three replications, with each genotype serving as a treatment. The experiment was planted in a 5-meter-long, 4row patch. Plants were spaced 10 cm apart, and rows were spaced 30 cm apart. To produce a competitive and robust crop strand, all cultural treatments necessary for a strong feed sorghum crop were used. During harvest, five competitive plants were chosen at random from each plot, and observations were made on these plants for several attributes. However, observations were made on a plot-byplot basis over the days leading up to 50% blooming. For statistical analysis, the average of these five plants with regard to various plant characteristics was utilized.

Observations on ten yield and yield attributing characters-Days to 50% flowering, Plant height (cm), Leaf breadth (cm), Leaf length (cm), Stem girth (mm), Leaves per plant, Leaf area (cm 2 ), Leaf stem ratio, Total soluble solids (%) and green fodder yield (g) were recorded. In this experiment statistical analysis was followed and replication wise mean data of thirty seven genotypes for ten characters are used for the statistical and biometrical analysis for the parameters-Analysis of variance as per the methods given by Panse and Sukhatme (1957) [14] and Genetic divergence analysis was done as per the Mahalanobis D 2 (1928) [11] statistics followed by the Rao (1952) [19] .

Results and Discussion

Analysis of variance showed that the highly significant mean differences were observed for all the ten characters under study i.e., days to 50% flowering, plant height, leaf breadth, leaf length, stem girth, leaves per plant, leaf area, leaf stem ratio, total soluble solids and green fodder yield per plant which indicated that substantial variability was present in the sorghum accessions selected for study and were suitable for further genetic and selection parameters. High amount of genetic variability for many of these traits has also been reported earlier by Parashuram et al. (2022) [15] , Bhadouriya & Bhadouriya (2024) [4] and Boratkar et al.

Based on D 2 values thirty seven genotypes of sorghum were grouped into six clusters using ten component characters.

Cluster I was the largest, comprising of fourteen genotypes followed by Cluster V with eight genotypes, Cluster III represented by six genotypes, Cluster VI have five genotypes, Cluster II with three genotypes, which concluded that in general, there was parallelism between genetic and geographic diversity. Cluster IV have one genotype which independently diverged from others (Table -2). Fourteen genotypes grouped under Cluster I which indicated their proximity and narrow genetic base. This view point has been supported by the works of Rajappa et al. (2024) [18] , Ahmad et al. (2025) [1] and Gebre et al. (2025) [8] . Genotypes belonging to cluster I (G-48, Pratap Chari-1080, Varsha, IC-0347570, UP Chari-2, CSV-17, Pant Chari-7, Pant Chari-4, IC-056030, IC-0568396, IC-0597651, UP Chari-4 and UP Chari-1) observed maximum genetic diversity within the cluster as compared to the genotypes belonging to other clusters. The maximum intra cluster distance (2.38) was recorded for cluster I followed by cluster II (2.32), cluster V (2.25), cluster III (2.03), cluster VI (1.91) while minimum intra cluster distance (0.02) was noted in case of cluster IV (Table -3). Maximum inter cluster distance revealed between cluster II and cluster IV (5.81) followed by cluster III and V (5.25), cluster IV and cluster VI (5.21) and the minimum inter cluster distance was found between cluster I and cluster VI (2.71). These results are in accordance with the findings of Pal et al. (2022) [13] , Arvinth et al. (2024) [2] , Patel et al. (2024) [16] and Santosh & Pandey (2024) [20] . (2023) [10] , Kiran et al. (2024) [9] and Navyashree et al.

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