Optimal window for seed physiological and harvestable maturity to maximise seed yield and quality in little millet (Panicum sumatrense Roth. ex Roem. & Schult.)

Little millet (Panicum sumatrense Roth. ex. Roem. and Schult.) is a climate-resilient, nutrient-rich crop, yet information is limited to its seed physiological maturity and optimal harvest stage, which are the key determinants for maximising seed yield and quality. Experiments across two post-rainy seasons with three cultivars (TNAU 63, Gujarat vari 1, DHLM 36-3) examined seed development and maturation behaviour from anthesis to maturity. Seed formation commenced at 7 days after anthesis (DAA) in year 1 but varied in year 2 (7–14 DAA) across cultivars. Seeds were harvested at weekly stages up to 56–63 DAA and assessed for seed physiological and biochemical traits. Seed moisture content declined and hardness increased steadily with maturity, while test weight, seed yield, germination, vigour and storability peaked between 35–42 DAA, marking physiological maturity at 35 DAA across cultivars in year 1 and at 35 DAA (Gujarat vari 1) or 42 DAA (TNAU 63, DHLM 36-3) in year 2, reflecting temperature-driven variation. Polynomial regression analysis further validated this maturity window. At physiological maturity, little millet panicles turn straw to dark brown, while the oval seeds appear smooth, shiny and streaked in shades of greenish brown to yellow. Upon de-husking, the seeds exhibited a brownish depression at the hilar end, which serve as reliable morphological marker of physiological maturity in little millet. Early harvests produced immature, low-vigour seeds, while delayed harvests reduced seed yield and quality due to seed shattering and deterioration. The study identifies 35–42 DAA as the physiological and harvestable maturity window for high-quality seed production in little millet.