Assessment of morphological diversity in sorghum genotypes through DUS descriptors

Introduction

Sorghum (Sorghum bicolor (L.) Moench) is an important cereal crop belonging to the family Poaceae and ranks as the fifth most important cereal globally. It is believed to have originated and been domesticated in Africa around 5000-8000 years ago, with the Indian subcontinent serving as a secondary center of origin where considerable genetic diversity is observed (Elangovan, 2010) [3] . Cultivated sorghum (S. bicolor subsp. bicolor) is diploid with chromosome number of, 2n = 2x = 20 and it follows the C 4 photosynthetic pathway unlike rice, which enables efficient carbon assimilation under high temperature conditions. The crop is well known for its outstanding agronomic performance and wide adaptability, as it can grow under diverse environmental conditions including drought, high temperatures, high altitudes, and saline-alkaline or marginal soils. Due to its resilience under adverse conditions, sorghum serves as an important "failsafe" crop in the global agroecosystem (Paterson, 2008) [7] . It is considered as a multipurpose crop used for food, feed, fiber, and bioenergy. The grain is utilized for human consumption and animal feed, while the stem serves as a source of fiber, fuel, and more recently, as feedstock for cellulosic ethanol production (Wang et al., 2016) [20] . Sorghum is called by different names across different regions as "great millet" and "guinea corn" in West Africa, "kafir corn" in South Africa, "dura" in Sudan, "mtama" in East Africa, "jowar" in India, and "kaoliang" in China (Sanjana Reddy, 2017) [14] . It is known as "king of millets" and in Ayurveda it is traditionally referred to as "Yavanala" (due to its nutritional properties) (Varshanth and Harikrishnan, 2025) [19] . Globally, Sorghum production is expected to reach 63.5 million metric tonnes in the 2025/2026 marketing year. India ranks fourth in position, contributing about 7% of overall production after the United States, Nigeria, and Brazil, with an estimated production of 4.6 million metric tonnes in approximately 4 million hectares area. (USDA-FAS, 2025) [18] . Genetic variability is a prerequisite for any crop improvement and it is primarily derived from germplasm resources. Germplasm represents the total gene pool of a species, including landraces, obsolete cultivars, wild relatives, and weedy forms, and, for efficient utilisation in breeding programs, it must be systematically evaluated, characterised, and documented.

In India, the Protection of Plant Varieties and Farmers' Rights (PPV&FRA) Act, 2001 [8] , grants intellectual property rights to plant breeders, researchers and farmers who develop new or extant plant varieties. Under this Act, varieties must fulfil the criteria of Novelty, Distinctness, Uniformity, and Stability (DUS) for registration. DUS testing plays an important role in knowing the identity and uniqueness of varieties by providing detailed characterisation, which is essential for their protection and identification. Sorghum is among the first 12 crop species notified for registration under the PPV&FR Act (Prajapati et al., 2018) [9] . Therefore, the present study was undertaken to evaluate and characterize sorghum germplasm based on 33 DUS descriptors in order to identify distinct, uniform, and stable genotypes for effective utilization in breeding programs.

Materials and methods

The experiment was conducted using 42 sorghum germplasm accessions (Table 1) during the kharif season of 2025-26 at the Regional Agricultural Research Station, Palem (16.51558 °N, 78.24911 °E). The experiment was laid out in a randomized complete block design (RCBD) with three replications. Each genotype was sown in three rows of 4 m length in each replication. Recommended agronomic practices, including application of fertilizers as per package of practices and intercultural operations such as thinning and weeding, were followed to raise a healthy crop. A total of 33 DUS descriptors were recorded at different stages of crop growth, primarily based on visual observations. The traits included seedling anthocyanin coloration of coleoptile, leaf sheath anthocyanin coloration, leaf midrib colour, time of panicle emergence, plant height up to base of flag leaf, flag leaf midrib coloration, lemma arista formation, stigma anthocyanin coloration, stigma yellow coloration, stigma length, flower length with pedicel, anther length, anther colour (dry), glume colour, total plant height, stem diameter, leaf blade length and width, panicle length (without peduncle), panicle branch length, panicle density at maturity, panicle shape, visible neck length of panicle above sheath, glume length, grain thresh ability, caryopsis colour after threshing, 1000-grain weight, grain shape (dorsal and profile), grain germ mark size, endosperm texture, grain colour of vitreous albumen, and grain lustre.

Results and discussion

The present investigation was carried out using 42 sorghum genotypes (Table 1). DUS descriptors were recorded for all genotypes following the guidelines provided in Plant Variety Journal of India (2007) to evaluate the extent of distinctiveness among them. A total of 33 morphological characters were observed and documented. The frequency distribution for each character was computed and presented in Table 2, and the genotypes exhibiting each state of the respective descriptors are presented in Table 3. For the trait seedling: anthocyanin colouration of coleoptile, the majority of genotypes (38) exhibited yellow-green colouration, whereas a smaller proportion (4) showed grayed-purple colouration. Similar findings were reported by Raghuvanshi et al. (2014) [10] , who observed that out of seventeen varieties studied, twelve exhibited green coleoptile colour, while the remaining five showed purple colouration. [9] . Bhusal et al. (2017) [1] reported that, based on the evaluation of 33 morphological characters, distinct features can be seen in five genotypes, namely S-540, SSG 59-3, COFS 29, HC 136, and IS 18551, for traits such as plant height up to the base of the flag leaf, days to panicle emergence, leaf blade width, and panicle density at maturity. Similarly, Sangwan et al. (2005) [13] observed that stem thickness was highest in PC 6 and lowest in PC [12] also reported variation in time of panicle emergence ranging from 65 to 87 days. Swamy et al.

(2018) [17] emphasised that days to 50 per cent flowering is an important trait, as it showed a significant and positive association with grain yield per plant. Similar findings were reported by Chavan et al. (2018) [2] , who observed traits such as grayed-orange colour of dry anther (53.85%) and yellow-white glume colour (30.77%) and other among the studied genotypes.

Similarly, based on flower length with pedicel, genotypes were classified into two categories: medium (24 genotypes; 57%) and long (18 genotypes; 42.9%). For anther length, 37 genotypes were categorized as short, while 5 were medium.

Regarding the colour of dry anther, most genotypes exhibited yellow-orange colouration (23 genotypes; 54.8%), whereas the remaining 19 genotypes (45.23%) showed grayed-orange colouration.

In the panicle traits, the panicle length (measured without peduncle) was grouped into short and medium categories. The majority of genotypes (34; 80.95%) exhibited medium panicle length (21-20 cm), while 8 genotypes (19.04%) were classified as short (11-20 cm). With respect to panicle branch length (measured from the middle third portion of the panicle), all genotypes exhibited medium length (5.1-10 cm). Similarly, all genotypes showed symmetric panicles. In terms of panicle compactness, 37 genotypes showed semiloose density at maturity, while 5 genotypes showed semicompact density. For panicle neck length (visible length above the sheath), variation was observed, with 20 genotypes (47.6%) falling under the short category ( [5] in their study on 26 forage sorghum varieties. Based on grain shape in dorsal view, three categories were observed: elliptic (26 genotypes; 62%), circular ( [11] and Elangovan et al. (2014) [4] , who evaluated 236 minicore accessions using 33 morphological traits. Their findings indicated the predominance of traits such as elliptic grain shape in dorsal view, elliptic grain shape in profile view, medium germ mark size, 25% corneous endosperm texture, grayed-orange colour of vitreous albumen, and non-lustrous grains among the accessions. Further, Santiya et al. (2025) characterized sorghum genotypes and identified promising grain types based on traits such as earliness (<64 days) and higher grain weight (>31 g), including genotypes like TNS 682 and RPHT 14. Similar characterization studies have also been reported in pearl millet by Nehra et al. (2016) [6] .

The findings of the present study are in close agreement with these reports, indicating that the observed variability and trait distribution follow similar patterns, thereby confirming the reliability and relevance of DUS-based characterization in sorghum

Conclusion

In the present study, 33 morphological DUS descriptors were employed to characterize the sorghum genotypes, showing considerable variation across different vegetative, flowering, panicle, and grain traits enabling effective grouping based on phenotypic similarities and differences. Such characterization provides a valuable foundation for selecting diverse parental lines in breeding pr ogrammes, thereby facilitating the creation of greater genetic variability through crosses selected between distinct groups and genotypes possessing contrasting traits. The variation observed from this study is useful not only for the development of new, distinct varieties but also for supporting cultivar improvement and germplasm conservation efforts aimed at enhancing sorghum productivity.

References

1. Bhusal N, Pahuja SK, Vats AK, Srivastava A, Kumar RS. Morphological characterization of forage sorghum genotypes for its various DUS traits. Journal of Applied & Natural Science. 2017 Jun 1;9(2):912-920.
2. Chavan LN, Patil SM, Kauthale VK, Nalawade AD. Morphological characterization of sorghum [Sorghum bicolor (L.) Moench] landraces using DUS descriptor. Agricultural Science Digest-A Research Journal. 2018 Sep 1;38(3):221-224.
3. Elangovan M, Prabhakar P, Chandra Sekara Reddy D. Characterization and evaluation of Sorghum [Sorghum bicolor (L.) Moench] germplasm from Karnataka, India. Karnataka Journal of Agricultural Sciences. 2010 May 21;20(4):710-713.
4. Elangovan M, Reddy GC, Babu PK, Rani MJ. Preliminary evaluation of mini-core collection of sorghum for utilization. In: Conference: Global Consultation on Millets Promotion for Health & Nutritional Security. Directorate of Sorghum Research. Hyderabad; 2014. p. 291-292.
5. Joshi DC, Shrotria PK, Singh R, Chawla HS. Morphological characterization of forage sorghum [Sorghum bicolor (L.) Moench] varieties for DUS testing. Indian Journal of Genetics and Plant Breeding (The). 2009;69(4):383-393.
6. Nehra M, Kumar M, Vart D, Sharma RK, Choudhary M. DUS characterization and diversity assessment in pearl millet inbreds. Electronic Journal of Plant Breeding. 2016;7(4):925-933.
7. Paterson AH. Genomics of sorghum. International Journal of Plant Genomics. 2008;2008(1):362451.
8. Protection of Plant Varieties and Farmers' Rights Authority (PPV&FRA). Guidelines for the conduct of test for distinctiveness, uniformity and stability on (Sorghum bicolor (L.) Moench). Plant Variety Journal of India. 2007;1(1):15-35.
9. Prajapati DK, Pahuja SK, Verma NK, Chaudhary S. Morphological characterization of sorghum [Sorghum bicolor (L.) Moench] germplasm for DUS traits. International Journal of Current Microbiology and Applied Sciences. 2018;7(2):2058-2071.
10. Raghuvanshi S, Swamy D, Mahadevakumar S, Singh OP. DUS discriptor of seventeen forage cultivars of sorghum [Sorghum bicolour (L.) Moench]. Global Journal of Bio-Science and Biotechnology. 2014;3:100108.
11. Reddy BV, Sharma HC, Thakur RP, Ramesh S. Characterization of ICRISAT-bred sorghum hybrid parents (set I). Patancheru: International Crops Research Institute for the Semi-Arid Tropics; 2006. p. 1-20.
12. Reddy BV, Ashok Kumar A, Sanjana Reddy P. Genetic improvement of sorghum in the semi-arid tropics. In: Genetic Improvement of Sorghum in the Semi-Arid Tropics. New Delhi: Academic Foundation; 2008. p. 105-233.
13. Sangwan VP, Chauhan P, Ram C. Varietal identification in forage sorghum through morphological characters. Haryana Agricultural University Journal of Research. 2005;33(1):117-118.
14. Sanjana Reddy P. Sorghum, Sorghum bicolor (L.) Moench. In: Millets and Sorghum: Biology and Genetic Improvement. Hoboken: John Wiley & Sons; 2017 Feb 28. p. 1-48.
15. Santhiya S, Kavithamani D, Selvi B. Classification of sorghum (Sorghum bicolor (L.) Moench) germplasm accessions for various agro-morphological parameters. Range Management and Forestry. 2025 Jun 1;46(1):5661.
16. Shafiqurrahaman M, Dahiya GS, Pahuja SK, Dehinwal AK, Arya RK. DUS characterization in sorghum [Sorghum bicolor (L) Moench.]. Forage Research. 2022 Mar;47(4):423-431.
17. Swamy N, Biradar BD, Sajjanar GM, Ashwathama VH, Sajjan AS, Biradar AP. Genetic variability and correlation studies for productivity traits in Rabi sorghum [Sorghum bicolor (L.) Moench]. Journal of Pharmacognosy and Phytochemistry. 2018;7(6):17851788.
18. United States Department of Agriculture -Foreign Agricultural Service (USDA-FAS). India Sorghum Production Data 2024/2025. Foreign Agricultural Service, United States Department of Agriculture; 2024. Available from: https://ipad.fas.usda.gov/countrysummary/Default.aspx ?crop=Sorghum&id=IN