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, particularly 2-phenylethyl isothiocyanate, from degrading root tissues. However, 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. Susceptibility to P. neglectus was not related to the total glucosinolate levels, but there were signifi- cant, negative correlations (r = -0.619, -0.517; P < 0.001) between root levels of 2-phenylethyl glucosinolate (isothiocyanate precursor) and plant susceptibility to P. neglectus: plants containing more than a certain threshold level of 2-phenylethyl glucosinolate showed reduced susceptibility to the nematode. Selection for high root levels of 2-phenylethyl glucosinolate should reduce the susceptibility of the plants during the growing season while also increasing the nematicidal impact of the degrading root tissues, thereby improving the suppressive benefits of the crop when used in rotation with cereals.