Screening of six cowpea lines against Meloidogyne javanica under greenhouse conditions 

Abstract

Cowpea (Vigna unguiculata (L.) Walp.) is an important grain legume widely cultivated in sub-Saharan Africa for food security, nutritional supplementation, income generation, and soil fertility improvement. However, productivity of the crop is severely constrained by root-knot nematodes (Meloidogyne spp.), particularly the thermophilic species Meloidogyne incognita, Meloidogyne javanica and Meloidogyne enterolobii. The objective of this study was to determine the host status of six cowpea lines against M. javanica under greenhouse conditions. Two greenhouse experiments were conducted at the University of Limpopo, South Africa, using a randomised complete block design with six treatments replicated six times. Fourteen days after sowing, each seedling was inoculated with 3,000 eggs plus second-stage juveniles (J2) of M. javanica. Nematode assessments were conducted 56 days after inoculation. Reproductive potential (RP) was calculated as the ratio of final nematode population density to fresh root mass. Significant differences (P ≤ 0.05) were observed among cowpea lines for nematode reproduction. All test lines supported nematode reproduction, with RP values consistently exceeding unity. The findings demonstrate that all evaluated cowpea lines were susceptible hosts to M. javanica and are therefore unsuitable for deployment in crop rotation systems aimed at suppressing root-knot nematode populations. The study highlights the importance of incorporating nematode resistance screening into cowpea breeding programmes to support the development of integrated nematode management strategies under climate-smart agricultural systems.