engleski

Biological control of chestnut blight: interaction of the pathogen-Cryphonectria parasitica with biocontrol agent-hypovirus and chestnut genotype

Chestnut blight, a disease of chestnuts, is caused by an aggressive fungus, Cryphonectria parasitica which was introduced from Asia to Europe. The pathogen has been a problem in Europe for decades, substantially reducing the number and yield of the trees. However, virulent strains of the fungus can be converted to hypovirulent ones by transmission of naturally occurring Cryphonectria hypovirus 1 (CHV1). The presence of this dsRNA virus reduces fungal virulence and the capacity to reproduce via spores. As a consequence of hypovirulence, infected trees usually recover or show much weaker symptoms of infection. A relatively high frequency of hypovirulent strains of the fungus and, consequently, recovered trees have been observed in naturally-growing Croatian chestnut populations. However, „Lovran marrons“, a special breed of chestnuts primarily grown for the production of large quality fruits, obtained through selection and propagated by grafting, do not seem to recover. A substantially higher incidence of active, expanding cankers was observed on marrons than on naturally-growing trees, although similar prevalence of C. parasitica vegetative compatibility types and similar prevalence of associated CHV-1 were detected on naturally-growing and marron trees. Therefore, the lack of naturally-occurring hypovirulence or differences in fungal population are not the cause for different response of marrons to the chestnut blight. Ecological and physiological differences were ruled out since maroons and naturally-growing trees are growing in close proximity and are of similar age. It seems that the marron genotype is especially vulnerable and its ability to recover is limited even when CHV-1 is widely widespread in C. parasitica population.

Cryphonectria hypovirus 1; fungus; population biology; recovery; susceptibility

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