A joint North-South research initiative involving Teagasc and Queen's University will tackle the old enemy - potato blight - which continues to threaten today's crops, writes Anthony King
THE ARRIVAL OF potato blight in 1845 left an indelible mark on this country. The Famine lasted fours years but blight didn't go away and today remains the most destructive disease of the potato. A joint North-South project is taking on this old foe however by tapping into advances in bioscience.
Dr Louise Cooke, an expert on potato blight, is excited about the new collaboration between her group at the Agri-Food and Biosciences Institute in Belfast and Teagasc in Carlow. "For many years we co-operated on an informal basis but hadn't any sort of joint funding," she says.
The Department of Agriculture and Food's Research Stimulus Fund has paved the way for all-Ireland research on the disease, and Dr Cooke says this is particularly timely given the emergence of a new strain of blight in Britain.
The blight organism, Phytophthora infestans, spreads in Ireland as wind-borne spores, produced asexually. These spores alight on leaf surfaces and cause new infections. Blight can also reproduce sexually, if its two sex partners hook up. Scientists call the partners type A1 and type A2. The new dominant strain in Britain is an A2 strain and is compatible with the A1 strains dominant in Ireland. Last year, the new A2 strain was found in Northern Ireland.
If mating occurs, the life-cycle of the disease in Ireland will change dramatically because it will give rise to oospores, resting bodies that survive in soil for up to four years. It's possible these spores could infect a potato crop before it emerges from the ground, which is something we've never had before, explains Denis Griffin, potato breeder with Teagasc. Up until now, Phytophthora infestans survived only in plant tissue.
Sexual reproduction would also give rise to strains that differ from both parents. Such strains might be particularly aggressive, resistant to fungicides, or more temperature tolerant, said Dr Cooke.
The joint project aims to predict the likelihood of oospores forming. It will also sample disease outbreaks to monitor the arrival of any new strains. Griffin says they will then devise control strategies and advise farmers on which chemicals to use and which potato varieties are most resistant. "Varieties which were resistant may no longer be resistant to a new strain," he explains.
Teagasc has a long history in potato-breeding, and bred the popular rooster, one of our more blight-resistant potato varieties. Part of the project will investigate how potatoes in breeding programmes will hold up to future strains.
Last year was particularly good for blight, and bad for potato farmers, due to high humidity and heavy rains. "Everyone thinks we have blight beaten but then a year like last year comes along," says Griffin. Without fungicides, severe blight infestations can reduce potato yields to nil, so scientists are eager to develop more resistant potato plants.
Teagasc is involved in the international consortium to sequence the potato genome. To facilitate potato-breeding, molecular geneticist Dr Dan Milbourne of Teagasc says they will mine the resulting genetic data for genes that confer disease-resistance.
"Once we identify genes, we can track them in parents and into the progeny in a potato breeding programme," says Milbourne. Genes conferring quality traits could also be tracked.
Potatoes grown at the time of the Famine were very susceptible to blight and people were dependent on one variety, lumpur. Also, there were no fungicides and people didn't link the brown blotches on leaves to the disease.
"They thought it was a secondary consequence of the potato being sick," explains Dr Cooke. Control was possible only when the true nature of the disease became understood.
Dr Cooke views blight as a food-security issue and says research remains vital. "If you just look at blight on the plant without characterising the pathogen, you may not know that it has changed until you run into problems."