Evaluation of cowpea germplasm for biomass production, seed yield, and southern root-knot nematode resistance

Sixteen forage cowpea [Vigna unguiculata (L.) Walp.] plant introduction (PI) lines were evaluated for agronomic traits and pest resistance in field and greenhouse experiments to enhance double cropping and cover crop rotation systems in northeast Texas and the southeastern United States. Cowpea cultivars 'Iron and Clay' and 'Combine, and one cowpea breeding line, TX-3, were included as controls. Cowpea lines were planted in a Darco loamy fine sand soil (a loamy, siliceous, semiactive, thermic Grossarenic Paleudult) in a randomized complete block design. Data collected in 2015 and 2016 included biomass, seed yield, and maturity stage. Plant introduction lines differed in biomass and seed production (P < .05) in both years. Biomass production ranked highest at 2,695 lb thy matter (DM) acre(-1) for PI 175963 in 2015 and 2,582 lb DM acre(-1) for PI 367863 in 2016. Seed yield ranked highest at 305 lb acre(-1) for PI 175963 in 2015 and 2,071 lb acre(-1) for PI 208845 in 2016. In a greenhouse study, 14 PI lines and two cowpea breeding lines, TX-505 and TX-3, were evaluated for susceptibility to the southern root-knot nematode (Meloidogyne incognita). Based on nematode reproduction and root galling, most of the PI lines were susceptible, while PI 367863 and TX-505 were resistant. Several PI lines were identified with improved biomass and seed production and one PI line and one breeding line with resistance to the southern root-knot nematode. These lines could be used in cowpea breeding programs to develop improved forage cowpea cultivars for double-cropping and crop-rotation systems in Texas and the southeastern United States.