Development of a tomato/root knot nematode bioassay to screen beneficial microbes.

In common with other root knot nematodes Meloidogyne hapla is a serious plant pest. A rapid screening system for candidate microbes that benefit plant growth is a first step to developing screening bioassays in other plant–nematode systems. Cultures of M. hapla established on tomatoes were used to define the nematode damage function, and required bioassay duration for this plant-pest system, followed by scale-up to a glasshouse level. The quantities of Meloidogyne inoculum were chosen such that they would cause minor, moderate or severe plant damage; hence the degree of protection afforded by the microbes in bioassays could be readily evaluated. An inoculation rate of 3542 eggs/plant caused a significant reduction in shoot weight (30%) and an increase in root galling in excess of 50%. Percentage of root gall and root gall index were good indicators of nematode impact and provide a relatively quick method of assessment.