Brown-top millet: an overview of breeding, genetic, and genomic resources development for crop improvement.

MAIN CONCLUSION: Brown-top millet is a lesser-known millet with a high grain nutrient value, early maturation, and drought tolerance that needs basic research to understand and conserve food security. Brown-top millet [Urochloa ramosa (L.)] is currently cultivated in some developing countries (especially in India) for food and fodder, although it is less known among the small millets. Like other millets, it contains macro- and micronutrients, vitamins, minerals, proteins, and fiber, all of which have rich health benefits. The nutritional importance and health benefits of brown-top millet are still unknown to many people due to a lack of awareness, wide cultivation, and research. Hence, this millet is currently overshadowed by other major cereals. This review article aims to present the nutritional, breeding, genetic, and genomic resources of brown-top millet to inform millet and other plant researchers. It is important to note that genetic and genomic resources have not yet been created for this millet. To date, there are no genomic and transcriptomic resources for brown-top millet to develop single nucleotide polymorphisms (SNP) and insertion/Deletions (InDels) for breeding studies. Furthermore, studies regarding nutritional significance and health benefits are required to investigate the exact nutritional contents and health benefits of the brown-top millet. The present review delves into the nutritional value and health advantages of brown-top millet, as supported by the available literature. The limitations of producing brown-top millet have been enumerated. We also cover the status of marker-assisted breeding and functional genomics research on closely related species. Lastly, we draw insights for further research such as developing omics resources and applying genome editing to study and improve brown-top millet. This review will help to start breeding and other molecular studies to increase the growth and development of this cereal.

Artificial hybridization techniques in small millets-A review.

Small millets are nutri-rich, climate-resilient food and fodder crops. They include finger millet, proso millet, foxtail millet, little millet, kodo millet, browntop millet, and barnyard millet. They are self-pollinated crops and belong to the family Poaceae. Hence, to widen the genetic base, the creation of variation through artificial hybridization is a prerequisite. Floral morphology, size, and anthesis behavior cause major hindrances in recombination breeding through hybridization. Manual emasculation of florets is practically very difficult; therefore, the contact method of hybridization is widely followed. However, the success rate of obtaining true F1s is 2% to 3%. In finger millet, hot water treatment (52°C) for 3 to 5 min causes temporal male sterility. Chemicals such as maleic hydrazide, gibberellic acid, and ethrel at different concentrations aid in inducing male sterility in finger millet. Partial-sterile (PS) lines developed at the Project Coordinating Unit, Small Millets, Bengaluru are also in use. The percent seed set in crosses derived from PS lines ranged from 27.4 to 49.4, with an average of 40.10%. In proso millet, little millet, and browntop millet, apart from contact method, hot water treatment, hand emasculation, and the USSR method of hybridization are also followed. A newly developed modified crossing method known as the Small Millets University of Agricultural Sciences Bengaluru (SMUASB) method in proso and little millets has a success rate of 56% to 60% in obtaining true hybrids. Hand emasculation and pollination under the greenhouse and growth chamber in foxtail millet with a success rate of 75% seed set is suggested. In barnyard millet, hot water treatment (48°C to 52°C) for 5 min followed by the contact method is often practiced. Kodo millet being cleistogamous, mutation breeding is widely followed to create variation. Most commonly, hot water treatment is followed in finger millet and barnyard millet, SMUASB in proso, and little millet. Although no specific method is suitable for all small millets, it is essential to identify a trouble-free technique that produces maximum crossed seeds in all the small millets.

Exploring the diversity of virulence genes in the Magnaporthe population infecting millets and rice in India.

Blast pathogen, Magnaporthe spp., that infects ancient millet crops such pearl millet, finger millet, foxtail millet, barnyard millet, and rice was isolated from different locations of blast hotspots in India using single spore isolation technique and 136 pure isolates were established. Numerous growth characteristics were captured via morphogenesis analysis. Among the 10 investigated virulent genes, we could amplify MPS1 (TTK Protein Kinase) and Mlc (Myosin Regulatory Light Chain edc4) in majority of tested isolates, regardless of the crop and region where they were collected, indicating that these may be crucial for their virulence. Additionally, among the four avirulence (Avr) genes studied, Avr-Pizt had the highest frequency of occurrence, followed by Avr-Pia. It is noteworthy to mention that Avr-Pik was present in the least number of isolates (9) and was completely absent from the blast isolates from finger millet, foxtail millet, and barnyard millet. A comparison at the molecular level between virulent and avirulent isolates indicated observably large variation both across (44%) and within (56%) them. The 136 Magnaporthe spp isolates were divided into four groups using molecular markers. Regardless of their geographic distribution, host plants, or tissues affected, the data indicate that the prevalence of numerous pathotypes and virulence factors at the field level, which may lead to a high degree of pathogenic variation. This research could be used for the strategic deployment of resistant genes to develop blast disease-resistant cultivars in rice, pearl millet, finger millet, foxtail millet, and barnyard millet.