TOLERANT ACTINIDIA SPECIES TO PYTHIUM HELICOIDES AND P. VEXANS CAUSING ROOT ROT

T. Yano, S. Shimizu, T. Miyoshi, N. Miyata, K. Immon, T. Shinozaki, H. Sawada, K. Kageyama
Pythium helicoides and P. vexans are recognized as pathogens causing root rot of kiwifruit in Japan (Shimizu et al., 2005). Symptoms of the disease, including wilt of leaves, appear in early summer, the end of rainy season, and heavily damaged trees finally die. PCR detection methods with species-specific primers have been developed to examine their existence in plant tissues (Shimizu et al., 2009). In this study, we evaluated the tolerance of Actinidia species to these pathogens by using the PCR and newly developed real-time PCR methods. Cut segments of one-year-old shoot and root tissue of A. deliciosa ‘Hayward’, A. chinensis ‘Golden-King’, A. arguta ‘Hirano’ and A. rufa ‘AR-2’ were inoculated with P. helicoides (H5) and P. vexans (Pym21). The degree of decay caused by P. helicoides was much higher than the decay caused by P. vexans in all Actinidia species. When distribution of the pathogens in tissues was examined using the PCR method, P. helicoides was detected from all parts of the shoot and root segments in A. deliciosa and A. chinensis. However, P. helicoides was detected only in the inoculated part for A. arguta and in half of both segments for A. rufa, respectively. On the other hand, P. vexans was detected only in the inoculated parts of both shoot and root segments in all tested Actinidia species. The results suggest that A. arguta and A. rufa might be tolerant to P. helicoides, and that more sensitive methods need to be developed to evaluate the tolerance of Actinidia species to P. vexans. Further investigations are also necessary to clarify the tolerance mechanism.
Yano, T., Shimizu, S., Miyoshi, T., Miyata, N., Immon, K., Shinozaki, T., Sawada, H. and Kageyama, K. (2011). TOLERANT ACTINIDIA SPECIES TO PYTHIUM HELICOIDES AND P. VEXANS CAUSING ROOT ROT. Acta Hortic. 913, 517-523
DOI: 10.17660/ActaHortic.2011.913.69
https://doi.org/10.17660/ActaHortic.2011.913.69
kiwifruit, root rots, resistance
English

Acta Horticulturae