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Grading of blight resistance in different chestnut accessions
- Bolvanský, M., Pazitný, J., Adamčíková, K.
- Acta horticulturae 2018 no.1220 pp. 87-94
- Castanea crenata, Castanea sativa, Cryphonectria parasitica, bark, blight, branches, humidity, hybrids, physiological state, pycnidia, screening, trees, virulence, wood
- Five chestnut trees (three hybrids Castanea sativa × C. crenata, one C. sativa and one C. crenata) with different levels of blight resistance were subjected to the screening by two virulent and one hypovirulent strains of Cryphonectria parasitica in order to examine reliability of ex situ tests for grading of blight resistance in chestnut. Branches 2-3 cm in diameter were harvested from the trees, in early April and end of September and stored at about 10°C for either 2 weeks (for branch sections) or 4 weeks (for bark- and wood-tissue sections). Branch sections and bark- and wood-tissue sections were inoculated with the C. parasitica strains and incubated in the dark at 25°C with 95% humidity for 4 weeks and/or 4 days, respectively. In branch sections, superficial cankers were very rare so only occurrence of pycnidia formed around the inoculating holes were evaluated. Pycnidia occurred more frequently in branch sections collected from the less resistant accessions in October trial. The size of necrotic areas reflected the resistance ranking of accessions in April/May better than in October inoculation trials. Results of inoculations on excised wood tissue were more consistent with the real blight resistance level than data obtained from inoculations on excised bark tissue. Occasional inconsistence between results of inoculations carried out at different dates or in different trees might be caused by different physiological state of collected branches. Based on these results it can be concluded that the end of dormant period seems to be the most suitable time to carry out both pathogenicity and resistance tests in chestnuts.