Inoculum levels of Meloidogyne hispanica and M. javanica affect nematode reproduction, and growth of tomato genotypes

Abstract

A pot experiment was conducted to determine the effects of three inoculum levels (2,500, 5,000 and 10,000 eggs/plant) on the reproduction of Meloidogyne hispanica and M. javanica isolates and growth of the susceptible tomato genotypes Easypeel and Moneymaker, and genotypes Motelle and VFnt-Cherr, which possess the Mi-gene, at 25±2°C. sixty days after inoculation, roots were assessed for gall index (Gi), reproduction factor (Rf=final/initial population density) and reproduction index (RI=Rf in the Mi-gene tomato plants/Rf in tomato Easypeel × 100). shoot and root lengths and fresh and dry root and shoot weights were also recorded. both species of Meloidogyne reproduced at all inoculum levels on all four tomato genotypes (4≤GI≤5 and 3.44≤Rf≤317.30). The M. javanica isolate, obtained from an infected potato field, was identified as natural and partially virulent to the Mi-gene (3.71≤RI≤20.19). This emphasizes the need for new sources of resistance to root-knot nematodes and for testing Mi-tomato plants for their susceptibility to local populations. Reproduction of M. javanica and M. hispanica on the resistant Motelle and VFNT-Cherr was significantly less than on the susceptible Easypeel and Moneymaker. VFNT-Cherr was more resistant than Motelle, which suggest an influence of the genetic background of the plants on the nematode response. For Easypeel and Moneymaker, there was a trend of decreased plant growth parameters with increasing inoculum level, irrespective of the nematode species, due to damage caused by the increasing number of nematodes that invaded plant roots. However, these values on Motelle and VFnt-Cherr remained relatively stable regarding shoot and total shoot plus root dry weight. the reproductive rate of M. javanica was greater than that of M. hispanica on all four genotypes tested, and tomato plants inoculated with M. hispanica had greater growth parameters. the resistance response of the Mi-tomato plants was independent of the Meloidogyne species, however, because both species gave similar Ris.