Resistance to Meloidogyne enterolobii and Meloidogyne incognita in Cultivated and Wild Cowpea

Cowpea [Vigna unguiculata (L.) Walp)] is a multipurpose crop that provides nutrients for human and livestock diets, as well as regulates and supports ecosystem services. In developing countries, cowpea is exploited as a dual-purpose crop for its grain and fodder; it is cultivated primarily for grain and as a cover crop in industrialized countries. However, root-knot nematodes (RKNs) (Meloidogyne spp.) represent a threat to cowpea production worldwide. Thus, we screened the University of California, Riverside (UC-Riverside), cowpea mini-core collection for resistance to Meloidogyne incognita Kofoid and White (Chitwood) and M. enterolobii Yang and Eisenback to verify the potential of this collection to be used for improving RKN resistance in cowpeas. Both screenings showed significant genotypic variation and medium/high broad-sense heritability (H-2) estimates for most traits, and several traits were also strongly correlated. For the M. incognita screening, 86.1% of accessions showed some level of resistance based on gall score (<= 3), and 77.7% based on reproduction index (RI) (25 <= RI <= 50), whereas only 10.4% and 29.8% of accessions were resistant to M. enterolobii based on gall score (<= 3) and RI (25 <= RI <= 50), respectively. These results demonstrate the greater virulence of M. enterolobii than M. incognita in cowpea, and that geographic origin of germplasm was not linked to sources of resistance. Among cultivars, only US-1136 showed resistance against both nematode species, whereas 12 wild/landrace germplasms exhibited resistance to M. incognita and M. enterolobii, and can be exploited for breeding resistant cowpeas.