Suppressive Effect of Brassica juncea on the Root-Lesion Nematode (Pratylenchus penetrans)

Incorporation of sulfur-rich crucifer tissues into soil is known to suppress a variety of soil-borne plant pathogens and pests. The potentials of using Brassica juncea as green manure to kill the root lesion nematode Pratylenchus penetrans in soil and to decrease damages to subsequent crops were assessed in field and pot experiments. In the first trial, green manures containing B. juncea were grown and incorporated during spring to summer 2009. Japanese radish was then cultivated in each plot. In the second trial in spring 2010, green manure was grown and incorporated during summer to autumn 2009, and greater burdock was cultivated in pots containing soil sampled from each plot. Neither trial showed clear effects on nematode populations in the soil. However, in the first trial, Japanese radish grown following a B. juncea breeding line with a high content of sinigrin had a lower root lesion index and a higher number of marketable taproots than grown in the fallow soil. In the second trail, greater burdock cultivated in pots following incorporation of B. juncea had a lower root lesion index with the incorporation of white mustard, which is widely used as a landscape plant. These findings suggest that B. juncea used as green manure can potentially decrease damage to subsequent crops caused by the root-lesion nematode, although it had no positive effect on decreasing populations of the root-lesion nematode in the soil.