Reduced susceptibility of Brassica napus to Pratylenchus neglectus in plants with elevated root levels of 2-phenylethyl glucosinolate

The effect of canola (Brassica napus) as a crop suppressive to Pratylenchus neglectus is in part due to the release of nematicidal isothiocyanates, pa rticularly 2-phenylethyl isothiocyanate, from degrading root tissues. Howev er, many cultivars of canola are relatively susceptible to P. neglectus and will fail to reduce soil populations of the nematode. A survey of B. napus accessions and closely related species revealed limited scope to decrease the susceptibility of canola through conventional intercrossing. Susceptibi lity to P. neglectus was not related to the total glucosinolate levels, but there were significant, negative correlations (r = -0.619, -0.517; P < 0.0 01) between root levels of 2-phenylethyl glucosinolate (isothiocyanate prec ursor) and plant susceptibility to P. neglectus: plants containing more tha n a certain threshold level of 2-phenylethyl glucosinolate showed reduced s usceptibility to the nematode. Selection for high root levels of 2-phenylet hyl glucosinolate should reduce the susceptibility of the plants during the growing season while also increasing the nematicidal impact of the degradi ng root tissues, thereby improving the suppressive benefits of the crop whe n used in rotation with cereals.