Molecular Characterization and Pathogenicity of Meloidogyne incognita on Tomato Cultivars (Solanum lycopersicon L.)

Abstract

The study was conducted to determine the distribution of the common Meloidogyne species in and around the Ibadan area in Oyo State, south‐west Nigeria, West Africa using Polymerase Chain Reaction (PCR), as well as determine the effect of Meloidogyne incognita on five tomato cultivars. The locations included Akobo 7°25′49.13″N; 3°56′ 55.44″E (a peri‐urban vegetable farm), Ijaye 7°50′48.60″N; 3°34′11.23″E, National Institute for Horticultural Research (NIHORT) 7°24′19.13″N; 3°50′57.01″E, International Institute of Tropical Agriculture(IITA), Ibadan 7°29′52.05″N; 3°54′ 19.16″E and inoculum plots of the Department of Crop Protection and Environmental Biology, University of Ibadan 7°27′4.14″N; 3°53′ 49.19″E. DNA was extracted from the bulk juveniles, according to modified (Dellaporta et al., 1983). Identification of species was carried out using Meloidogyne species universal primer 194/195 and specific SCAR primers MIF/MIR. The nucleic acid was size‐fractioned in 1% agarose gel, stained with 4 μl ethidium bromide and captured by the ultraviolet light. Meloidogyne incognita produced amplification fragments of 720‐bp and 999‐bp for 194/195 and MIF/MIR primers, respectively. Meloidogyne incognita and javanica were the predominant species of root‐knot nematodes identified from the collected samples. The pathogenicity of Meloidogyne incognita was evaluated at different egg mass inoculum levels on five tomato cultivars in the screenhouse in (IITA). All growth parameters such as plant height, leaf number, and yield responded negatively with increasing inoculum levels for all the cultivars except Small Fry VFN and Celebrity cultivars which were found to be resistant based on (Soriano et al., 2000) resistance rating. The results also showed that the Ibadan Local cultivar was the most susceptible to M. incognita. The reproductive factor of the nematode (RF) was determined according to (Oostenbrink, 1966). The root galling index was rated on a 0–5 scale, where 0=0% galled roots; 1= < 10%, 2= 10–25%, 3= 25–50%,4=50–75% and 5= > 75% galled roots (Soriano et al., 2000). All data were analyzed by analysis of variance using SAS 9.2 version and means were separated using Least Significant Difference (LSD). In conclusion, the common meloidogyne species distribution in south‐west Nigeria was determined and this is very important in the formulation of management tactics against this pathogen.Support or Funding InformationThe research was supported by Alliance For A Green Revolution in Africa (AGRA)