ABSTRACT.
Evaluation of root-knot nematodes (Meloidogyne spp.) population density for disease resistance screening of tomato germplasm carrying the gene Mi-1

Beatriz Padilla-Hurtado1, 3, Yacenia Morillo-Coronado2, Sandra Tarapues1, Santiago Burbano1, Mauricio Soto-Suárez2, Ramiro Urrea1, and Nelson Ceballos-Aguirre1*
 
The root-knot nematode Meloidogyne spp. causes yield losses of up to 68% on tomato (Solanum lycopersicum L.) crops. Genetic resistance in the host plant makes the crop sustainable and it can breakdown when there is a high population density of the pathogen. The objective of this study was to determine the nematode population density that allow determining the resistance potential of tomato germplasm associated with the Mi-1 resistance gen. The Mi-1 gene was evaluated with the molecular marker SCAR Mi-23 and specific primers in the genotypes COLY007, IAC1687, LA0445, IAC1622 and two commercial controls (susceptible and resistant). The damage scale and the number of individuals recovered (eggs and juveniles) were assessed, with different population densities of the pathogen inoculated (0, 1000, 2000, 3000, 4000 and 5000 individuals plant-1), in a split plot design, with six replicates and a plant as the experimental unit. The genotype IAC1687 and the resistant commercial control presented the resistance allele of the Mi-1 gene and were classified as moderately resistant to a density of 1000 individuals plant-1. Despite having the Mi-1 gene, the COLY007 genotype was classified as moderately susceptible and with densities greater than 1000 individuals plant-1 can break resistance in all genotypes evaluated. Additionally, it is necessary to correlate the genotypic and phenotypic responses to guarantee the success of the selection supported by molecular markers such as SCAR Mi-23 and identify promising genotypes that could be included in a long-term breeding and also used as rootstocks in an integrated management of root-knot nematode
Keywords: Genetic resistance, genotype-phenotype association, Mi-23 molecular marker, radical nodulation susceptibility.
1Universidad de Caldas, Doctorado en Ciencias Agrarias, Facultad de Ciencias Agropecuarias, Calle 65 No. 26-10, Manizales, Colombia.
*Corresponding author (nelson.ceballos@ucaldas.edu.co).
2Corporación Colombiana de Investigación Agropecuaria-AGROSAVIA, km 14 Vía Mosquera, Bogotá, Colombia.
3Universidad Católica de Manizales, Instituto de Investigaciones en Microbiología y Biotecnología Agroindustrial, Carrera 23 N° 60-63. Manizales, Colombia.