Regional variation among Fusarium spp. causing dry rot of potatoes

This project was conducted by Sutton Bridge Crop Storage Research (SBCSR) and the James Hutton Institute (JHI) formerly SCRI. The findings combined with data on the susceptibility of cultivars to dry rot and the effect of fungicides on the different Fusarium spp., has been used to develop control recommendations for the disease.

Results

Over the 3-year survey (2001-2003) 10,950 tubers were collected and processed to recover dry rot-producing pathogens. In total, 217 Fusarium isolates were recovered. Fusarium coeruleum was the most commonly isolated species in each survey year. On average, Fusarium culmorum and avenaceum were the next most common species, but their prevalence varied greatly by season.

Fusarium sulphureum was the least common species on average. However, the proportion of F. sulphureum recovered compared with the other species remained remarkably consistent, comprising around 13% of the Fusarium species isolated. Selected isolates were evaluated for their ability to produce rots in planta using potato tubers. Fusarium sulphureum was a more aggressive pathogen (producing larger rots) than the other Fusarium species tested. In conventional pathogenicity tests, F. avenaceum and F. culmorum, were relatively weaker pathogens. However, these species were aggressive on some cultivars, notably Hermes. An attempt has been made in this report to quantify the importance of different species in the Fusarium-dry rot complex for the main potato cultivars tested.

The selected isolates were also assessed for their sensitivity to the fungicides, thiabendazole and imazalil. Experiments were conducted to ascertain the effect of storage temperature (4, 7 and 10°C) on the development of dry rot caused by different Fusarium species. Generally, the extent of rot development increased with increasing temperature.