The complete chloroplast genome sequence of Japanese Millet Echinochloa esculenta (A. braun) H. scholz (Poaceae)

Drought resistance strategies in minor millets: a review

MAIN CONCLUSION

The review discusses growth and drought-response mechanisms in minor millets under three themes: drought escape, drought avoidance and drought tolerance. Drought is one of the most prominent abiotic stresses impacting plant growth, performance, and productivity. In the context of climate change, the prevalence and severity of drought is expected to increase in many agricultural regions worldwide. Millets (coarse grains) are a group of small-seeded grasses cultivated in arid and semi-arid regions throughout the world and are an important source of food and feed for humans and livestock. Although minor millets, i.e., foxtail millet, finger millet, proso millet, barnyard millet, kodo millet and little millet are generally hardier and more drought-resistant than cereals and major millets (sorghum and pearl millet), understanding their responses, processes and strategies in response to drought is more limited. Here, we review drought resistance strategies in minor millets under three themes: drought escape (e.g., short crop cycle, short vegetative period, developmental plasticity and remobilization of assimilates), drought avoidance (e.g., root traits for better water absorption and leaf traits to control water loss), and drought tolerance (e.g., osmotic adjustment, maintenance of photosynthetic ability and antioxidant potential). Data from 'omics' studies are summarized to provide an overview of the molecular mechanisms important in drought tolerance. In addition, the final section highlights knowledge gaps and challenges to improving minor millets. This review is intended to enhance major cereals and millet per se in light of climate-related increases in aridity.

Genetic and genomic resources, and breeding for accelerating improvement of small millets: current status and future interventions

Current agricultural and food systems encourage research and development on major crops, neglecting regionally important minor crops. Small millets include a group of small- seeded cereal crops of the grass family Poaceae. This includes finger millet, foxtail millet, proso millet, barnyard millet, kodo millet, little millet, teff, fonio, job’s tears, guinea millet, and browntop millet. Small millets are an excellent choice to supplement major staple foods for crop and dietary diversity because of their diverse adaptation on marginal lands, less water requirement, lesser susceptibility to stresses, and nutritional superiority compared to major cereal staples. Growing interest among consumers about healthy diets together with climate-resilient features of small millets underline the necessity of directing more research and development towards these crops. Except for finger millet and foxtail millet, and to some extent proso millet and teff, other small millets have received minimal research attention in terms of development of genetic and genomic resources and breeding for yield enhancement. Considerable breeding efforts were made in finger millet and foxtail millet in India and China, respectively, proso millet in the United States of America, and teff in Ethiopia. So far, five genomes, namely foxtail millet, finger millet, proso millet, teff, and Japanese barnyard millet, have been sequenced, and genome of foxtail millet is the smallest (423-510 Mb) while the largest one is finger millet (1.5 Gb). Recent advances in phenotyping and genomics technologies, together with available germplasm diversity, could be utilized in small millets improvement. This review provides a comprehensive insight into the importance of small millets, the global status of their germplasm, diversity, promising germplasm resources, and breeding approaches (conventional and genomic approaches) to accelerate climate-resilient and nutrient-dense small millets for sustainable agriculture, environment, and healthy food systems.

Barnyard Millet for Food and Nutritional Security: Current Status and Future Research Direction

Barnyard millet (Echinochloa species) has become one of the most important minor millet crops in Asia, showing a firm upsurge in world production. The genus Echinochloa comprises of two major species, Echinochloa esculenta and Echinochloa frumentacea, which are predominantly cultivated for human consumption and livestock feed. They are less susceptible to biotic and abiotic stresses. Barnyard millet grain is a good source of protein, carbohydrate, fiber, and, most notably, contains more micronutrients (iron and zinc) than other major cereals. Despite its nutritional and agronomic benefits, barnyard millet has remained an underutilized crop. Over the past decades, very limited attempts have been made to study the features of this crop. Hence, more concerted research efforts are required to characterize germplasm resources, identify trait-specific donors, develop mapping population, and discover QTL/gene (s). The recent release of genome and transcriptome sequences of wild and cultivated Echinochloa species, respectively has facilitated in understanding the genetic architecture and decoding the rapport between genotype and phenotype of micronutrients and agronomic traits in this crop. In this review, we highlight the importance of barnyard millet in the current scenario and discuss the up-to-date status of genetic and genomics research and the research gaps to be worked upon by suggesting directions for future research to make barnyard millet a potential crop in contributing to food and nutritional security.