Enhancing limited resource farmer's ability to produce quality seeds through assessment of cowpea seed developmental physiology

Small-scale, on-farm seed production is gaining interest in many regions worldwide. However, seed production in zones with elevated temperatures and relative humidity can affect ultimate seed development and quality. This study explored the developmental physiology of Mississippi Purple cowpea seeds to clarify traits associated with seed quality while defining minimum safe harvest timing and vigor of mature seeds. Seeds were planted on three farms (Gainesville, FL), and plants were cultivated according to farmer-specific management practices. Developing seeds were harvested at eight intervals starting 15 days after anthesis (DAA). Evaluations of quality traits, including water relations, chlorophyll fluorescence, seed size, and germination, were performed at each harvest period. We found negligible to large farm effects on seed quality traits that depended greatly on seed production season. Nonetheless, seed moisture content, seed water potential, seed size, and germination were key traits defining a seed harvesting window. The earliest time for harvest was 35 DAA when seeds reached physiological maturity and attained maximum viability. We concluded seeds should not be harvested when moisture content is >0.30 g g⁻¹ or water potential >−90 MPa. Seeds ≤35 DAA can germinate but may not develop into seedlings. Seeds harvested at 45 DAA exhibited high vigor with the median time (P₅₀) for seed germination to decrease to 50%, ranging from 140 ± 3 to 174 ± 2 (mean ± SD) days. Our results demonstrate that cowpea seed production is achievable in an otherwise warm, humid climate.