Distribution and characterization of cowpea genotypes for resistance to rootknot nematodes (Meloidogyne spp.) in Mozambique

Cowpea (Vigna unguiculata (L.) Walp.) is an important food crop in Mozambique. The crop is cultivated almost exclusively by smallholder farmers in warm marginal environments of the country. One of the key field hindrances to the success of this crop are rootknot nematodes (Meloidogyne Spp.), that reduce cowpea yield. A study was conducted to establish rootknot nematode distribution, damage intensity (measured by incidence and severity), species identification and cowpea genotypes‟ resistance to Meloidogyne javanica. To assess rootknot nematode distribution and extent of damage, main cowpea growing areas including eight districts in three provinces (Gaza, Inhambane and Nampula) of Mozambique were selected. Rootknot nematode incidence in cowpea was recorded as the percentage of cowpea plants infested with rootknot nematodes. Severity of rootknot damage was achieved by scoring for the extent of rootknot nematode galling on roots of cowpea plants. Out of the 72 cowpea fields surveyed, 56.9% were infested with rootknot nematodes, with cowpea fields from Inhambane province registering the highest cases of rootknot nematode infestation. M. incognita, M. javanica, and M. enterolobii were identified to be associated with cowpea rootknot. The highest frequency of M. incognita and M. javanica was observed in cowpea fields from Inhambane and Gaza provinces, respectively. The 3 species generally occurred more frequently in Inhambane than the rest of the provinces. Generally, rootknot nematode galling score across provinces was low, with 1.9 as the highest gall index score obtained at province level. The highest mean rootknot galling score was observed in Homoine district. To characterize cowpea for resistance to rootknot nematodes (M. javanica.), twenty five cowpea genotypes from a Cowpea Breeding Program of the Faculty of Agronomy and Forestry Engineering at Eduardo Mondlane University, Maputo Mozambique, were used in an experiment conducted at Mozambique Agricultural Research Institute (IIAM). A randomized complete block design was used, where each genotype was replicated three times. Out of the twenty five cowpea genotypes assessed, four were found to be resistant, sixteen were tolerant and five were susceptible.