Search
Search Results
-
The specification of the growing temperature on PDA of chestnut blight pathogen (Cryphonectria parasitica (Murr.) Barr) to optimize timing for biocontrol treatments by hypovirulent strains
29-32Views:161The most destructive pathogen for the European chestnut trees is the blight fungus Cryphonectria parasitica (Murr.) Barr. The biological control is the only effective possibility to apply in situ biocontrol by hypovirulent strains against compatible virulent (wild) fungus strains. The infested bark tissues can inoculate by drilling holes surrounding and putting into agar discs interwoven by the appropriate vegetative compatible group (VCG) hypovirulent fungus strains. This latest can pass those virus-like particles (VLPs) by parasexual contact (called hypha-anastomosis)which responsible to hypovirulence. A laboratory experiment was made to find the optimal times to carry out the treatments. The intensity of growth of fungal colonies were analysed on different temperatures. The growth of the fungus on low temperature were rather slow,according to our expectations. On higher temperature the colony progress were the same as on the optimal 20–25 °C. These observations and the environment determine the date of the field applications under Hungarian weather conditions. It means the optimal treatment periods can be May or end of September to middle October in Hungary.
-
75 years of the chestnut blight fungus Cryphonectria parasitica (Murr.) Barr in Europe
82-85Views:171The chestnut blight fungus Cryphonectria parasitica is a native pathogen in East Asia and has been introduced into North America and Europe. Historical records and population genetic studies revealed at least three major introduction events from Asia into Europe.
Nowadays, chestnut blight is present in almost the entire distribution range of European chestnut, i.e. from the Iberian Peninsula to the Caucasus. The C. parasitica population in most countries has been studied in respect to the diversity of vegetative compatibility (vc) types and the occurrence of hypovirulence. The vc type diversity of the different populations varied considerably. Typically, a high diversity of vc types has been found in areas with a long history of chestnut blight and where sexual recombination between divergent genotypes commonly has occurred. On the other hand, newly established populations often showed a low diversity with only one, or a few vc types present.
Hypovirulence, i.e. the occurrence of C. parasitica isolates infected by Cryphonectria hypovirus 1 has been found widespread in Europe. Natural dissemination and active biological control applications have lead to a high prevalence of the hypovirus and to the recovery of many chestnut stands. Virulent cankers became hypovirus-infected within a short time and ceased expansion. There is concern that the diversity of vegetative compatibility types could increase in Europe through sexual reproduction between C. parasitica genotypes originating from different introductions. A higher level of vegetative incompatibility would not only hamper hypovirus spread within a population but could also select for lower virulence in CHV-1 and subsequently lead to an erosion of biological control. Recent studies, however, indicate that the vc type barriers are not so restrictive than previously assumed and that so far no evidence for an erosion of biological control system in high diversity populations can be observed.