Optimisation of culture conditions for in vitro infection of tomato with the root-knot nematode Meloidogyne javanica

Abstract

Conditions for in vitro culture of tomato seedlings (Lycopersicon esculentum) were optimised to yield high in vitro rates of infection by the root-knot nematode Meloidogyne javanica. The influence of nutrient salts, gelling agents, sucrose concentration and pH on the development of nematode-induced root galis was investigated. A quarter-strength Murashige and Skoog medium supplemented by 0.5% sucrose and solidified with 0.6% phytagel at pH 6.4 gave most galis on tomato roots. Eggs were sterilised in 2.5% sodium hypochlorite for 4 min followed by 0.2% mercuric chloride for 4 min. Surface-sterilised eggs showed a 16% cumulative hatching rate within 10 days. Tomato seedlings cultivated in vitro for 1 week were inoculated with sterile eggs and the infection process was monitored weekly. After 5 to 7 weeks, sterile egg masses were harvested, second-stage juveniles were hatched in sterile distilled water and used to re-inoculate tomato seedlings without further sterilisation. The culture conditions described gave similar infection results for the related root-knot nematodes M. incognita, M. arenaria and M. hapla.