Hatching of Globodera pallida is inhibited by 2-propenyl isothiocyanate in vitro but not by incorporation of Brassica juncea tissue in soil

The aim of this study was to assess the feasibility of controlling the potato cyst nematode Globodera pallida through biofumigation with glucosinolate-rich Brassica juncea genotypes. The main glucosinolate of B. juncea is 2-propenyl glucosinolate which is the precursor of 2-propenyl isothiocyanate. Toxicity of 2-propenyl isothiocyanate to encysted G. pallida was tested in vitro. Fifty percent reduction in hatching was found within 2 h of exposure to 0.002% 2-propenyl isothiocyanate. Based on the in vitro results, we hypothesized that biofumigation with B. juncea would reduce hatching of G. pallidain vivo and higher 2-propenyl glucosinolate levels would have a stronger effect. Plant genotype, sulfur fertilization and insect herbivory affected 2-propenyl glucosinolate concentration of B. juncea. However, increasing 2-propenyl glucosinolate concentration of B. juncea did not affect G. pallida hatching after biofumigation. The absence of a biofumigation effect was most likely due to lower concentrations of 2-propenyl isothiocyanate in vivo compared to in vitro conditions. These results show that it is difficult to reach sufficiently high levels of toxicity to reduce hatching of G. pallida under realistic conditions