Nematode inoculation conditions, plant growth periods and soil environments influence the parasitism of Meloidogyne incognita on tomato

Abstract

Meloidogyne incognita causes root-knot disease on various crops worldwide. The study of M. incognita pathogenicity has focused on the tomato pathosystem for several decades. However, inoculum parameters such as density and depth, as well as soil environments, vary across publications. This makes it impossible to analyse and compare the results across experiments. In this study, we explored the optimal inoculation conditions and soil environments by analysing the infection dynamics and reproduction of M. incognita . The number of infections continuously increased after inoculation until 5 days post inoculation, after which it decreased. The numbers of invading nematodes and formed eggs increased with the increase of inoculum density. However, inoculation with 800 second-stage juveniles (J2) per plant resulted in a reduced reproduction factor. An inoculation depth of 40 mm and a seedling growth period of 15 days resulted in the highest number of invading juveniles. Meanwhile, 15-day-old seedlings supported the largest reproductive population of nematodes. Hatched J2 retained most of their pathogenicity when stored at 25°C for up to 3 days. The water-holding trays were drained starting 1 day before inoculation to maximise J2 infection efficiency. Application of 50 ml of 0.6 g l −1 NPK (20:20:20) solution to each seedling at 2-3 day intervals after transplanting significantly promoted the reproduction of M. incognita . Peat was the most suitable substrate for nematode development, while sandy soil was the most commonly used because it was easy to wash away from tomato root surface. Our study provides detailed insights into nematode infection, which helps to standardise the inoculation conditions and soil environments for M. incognita research.