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ISHS Acta Horticulturae 1220: VI International Chestnut Symposium

Testing chestnut hybrids for resistance to Cryphonectria parasitica

Authors:   D. Chira, R. Teodorescu, C. Mantale, F. Chira, G. Isaia, G. Achim, A. Scutelnicu, M. Botu
Keywords:   interspecific hybrid chestnuts, resistance to Cryphonectria parasitica
DOI:   10.17660/ActaHortic.2018.1220.17
Asiatic pathogen Cryphonectria parasitica produced dramatic diebacks of American chestnut (Castanea dentata) and European or sweet chestnut (Castanea sativa) throughout their natural or artificial range, both in forests and orchards. Fungus chemical treatment is a useless (curative) to a less important (preventive) tool. Biological control of Cryphonectria parasitica has various levels of efficiency (from very good to very low), according to compatibility of local strain and fungus mycoviruses. In Romania all the sweet chestnut orchards have been largely destroyed. Till now, searching for natural resistance of European and American chestnut has largely failed. Therefore, chestnut breeding in order to improve resistance to pathogen is imperative both for horticulture and silviculture. In this paper, we tested transferring resistance to C. parasitica from Japanese (Castanea crenata) to European chestnut (C. sativa) in the Carpathian basin, Romania. Open pollinated interspecific hybrids (C. crenata C. sativa and C. sativa C. crenata) have been used as tested variants. Sweet chestnuts seedlings of local origin were used as a first control; the second control was a sweet chestnut forest situated at 50 km from the breeding trial. All chestnut material has been under pressure of Cryphonectria parasitica natural infection. We used several characteristics to evaluate the chestnut resistance: presence of fungus (fruitbody, mycelium, and infections), cankers, shoot/branch/stem infections, water sprouts, secondary woody fungus. Complementary, we tested the biological control of C. parasitica. Hybrids' resistance to Cryphonectria parasitica looked very promising, with just a small number of hybrids developing fruit bodies or cankers. On the contrary, first control sweet chestnut collections were severely damaged by the Asian pathogen. Biological control was very efficient both in European chestnut and interspecific hybrids. The untreated forest (second control) was dramatically affected by the fungus. At present, the health status of the chestnut hybrids is very good, showing a very good acclimatization in Carpathian continental climate.

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