Stop the rot!

The results of a four-year project to test the validity of hotbox tests, which can predict the suitability of seed potatoes for export, have now been confirmed. This project was undertaken by by the Applied Plant Science Division of the Department of Agriculture and Rural Development,

The hotbox test, which is used to detect the presence of latent rots in potatoes, involves placing a sample of tubers in a box under warm, humid conditions, to replicate what occurs when potatoes are placed in containers for shipment.

This hotbox test system is an important development for the seed potato export industry here, as Northern Ireland currently exports seed potatoes to a number of countries world-wide, including Morocco, Canary Islands, Portugal, Cyprus, Balearics, Algeria and Irish Republic.

During a four-year period (2001-2005), samples from Northern Ireland seed potato stocks destined for foreign shipment, have undergone these hotbox tests at APSD, Newforge Lane, to determine if latent diseases were present.

At the same time, validation trials were carried out to determine if the level of rots found in seed samples after export, were similar to that found in hotbox tests performed at Newforge.

Good agreement was obtained between hotbox tests and the quality post-shipment; the test is now fully validated. The number of samples submitted by seed growers for testing has increased from 50 in 2001 to 105 in 2004.

The test is good at determining the presence of latent blight and soft rot in stocks and the addition of standardised damage to tubers before hotboxing has allowed for the detection of dry rot and gangrene.

Dataloggers, electronic devices to measure temperature and humidity over preset time periods, were placed in shipping containers along with seed potatoes, during validation trials. These showed that high levels of relative humidity occur. The effect of placing a chemical desiccant in containers along with seed potatoes was investigated recently. Whilst the desiccant slightly lowered relative humidity levels and enchanced the overall presentation of tubers, there was little reduction in the level of rots found in some sample stocks.

While this hotbox test is not a statutory obligation, and is carried out on a voluntary basis by seed potato producers, the results of this trial emphasise the need for good practice in relation to all elements of seed production. Seed quality comes from the grower, who must pay attention to the basic aspects of seed production:-