Impact of the genetic diversity of three cyst nematodes on the effectiveness of root exudates to induce hatching

European Journal of Plant Pathology - Cyst nematodes are sedentary endoparasites of plants which cause important economic losses worldwide. New nematode control measures are needed since the...     

Evidence of strong gene flow among French populations of the carrot cyst nematode Heterodera carotae

The recent ban of the most efficient chemical nematicides has left growers without methods for controlling the carrot cyst nematode Heterodera carotae. This phytoparasitic nematode species has a very narrow host range and causes severe crop losses in the main carrot-growing regions worldwide. The development of alternative means of management of H. carotae is thus essential, and knowledge is required about the adaptive abilities of H. carotae, which mainly depend on gene flow among populations. The goal of this study was to describe the genetic structure of H. carotae populations at the spatial scale of the main infested French carrot-producing region, i.e. Lower Normandy, and to disentangle the causes of the heterozygote deficit in this polyvoltine species. Microsatellite genotyping of populations collected at both the plant and field scales showed that: (i) the heterozygote deficit is mainly due to substructure; and (ii) there is strong gene flow among populations, leading to low F_ST and to no clear genetic structure at the spatial scale explored here. Soil transport through both agricultural machinery and the transport of leek seedlings is probably responsible for the very strong H. carotae migration among fields and production areas. Measures should be considered to limit the passive spread of H. carotae.     

Humoral and cell-mediated immune responses of d/d histocompatible pigs against classical swine fever (CSF) virus

A better understanding of cell-mediated immune responses to classical swine fever virus (CSFV) is essential for the future development of improved vaccines. We analyzed the generation of cell-mediated and humoral immune responses in d/d histocompatible pigs following CSFV infection or vaccination. Viral infection induced high T cell responses with high primary and secondary CTL activity correlated with high IFN-gamma production, whereas vaccination with a live vaccine followed by infection mainly induced neutralizing antibody but low cell-mediated responses. Moreover, high IgG1 response was associated with high IFN-gamma response following infection whereas a weak IFN-gamma response was related to a good IgG2 response but a low IgG1 production. These data could reflect Th1/Th2-like balance of immune responses depending upon immunization protocols, which has not yet been described in the pig. T-cell responses to CSFV were evidenced by CSFV-specific CD25 upregulation on CD4-CD8+, but not on CD4+CD8- cells, which further illustrated the importance of CTL responses after infection. Our results indicated that generation of cell-mediated immune responses was much higher following intranasal/oral CSFV infection than after intramuscular vaccination, which implies that the capacity of new CSFV vaccines to induce higher T-cell responses should be considered.