Published Date: 2013-01-11 11:30:39
Subject: PRO/PL> Late blight, potato: new strains threat
Archive Number: 20130111.1492024
LATE BLIGHT, POTATO: NEW STRAINS THREAT
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Fri 4 Jan 2013
Source: FreshPlaza [edited]
According to the James Hutton Institute, the Sainsbury Lab, and other partners, potato blight is still a major threat to global food security in the 21st century. It is a particular problem today for emerging countries in Africa and Asia.
Through DNA-based forensic analysis, Dr David Cooke and partners describe the emergence and spread of highly aggressive lineages of the pathogen that have rapidly displaced other genotypes in Europe, making the disease more difficult to manage.
Cooke explained: "Pest and pathogen losses jeopardise global food security, as proven by the devastating spread of late blight across European crops back in 1845. The new lineage raises a worldwide food security issue as it has already spread beyond Europe, where it was 1st detected, to North Africa, India and China, threatening the livelihoods of communities relying on potato for food and income."
He says the disease is more difficult to control as it is more aggressive, fungicide resistant, and able to attack cultivars previously not considered susceptible to blight. "In a very wet [growing season], any weakness in the control strategy is exploited by the pathogen, resulting in severe crop losses."
[Potato late blight (PLB) is caused by the fungus-like organism _Phytophthora infestans_ and can cause 100 percent crop loss. The pathogen can also affect tomato and some other solanaceous crops. In potato, it affects leaves as well as tubers, and in tomato, it causes lesions and rotting of leaves, stems, and fruits. The disease can spread rapidly within a crop and destroy it within a few days. Under favourable conditions, epidemics in tomatoes may be even more rapid than in potatoes.
PLB is spread by plant material (including plant debris and volunteer crop plants), wind, and water. Disease management requires an integrated approach and may include removal of pathogen reservoirs, crop rotation, preventative fungicide treatments of planting material (potato seed tubers, tomato transplants), and fungicide sprays of crops. Late blight is considered an increasing problem worldwide, and seed tuber certification schemes have been set up in many countries as an important part of PLB management.
Considerable variation in aggressiveness between different pathogen strains has been observed, but more virulent strains are emerging frequently. Where both A1 and A2 mating types of the pathogen are present, reproduction occurs sexually as well as asexually, increasing the chances of strains with additional fungicide resistances and increased yield losses developing.
It has been reported that regional differences in pathogen population diversity no longer exist in Europe, where strains like Blue 13 (ProMED-mail posts 20090406.1332 and 20100212.0505) and Pink 6 (ProMED-mail post 20100604.1851) are now dominating, and further strains, such as the new Green 33 (ProMED-mail post 20120202.1031230), are emerging. Clean planting stock and management strategies for fungicide resistance of the pathogen are considered vital to control PLB outbreaks in the future. Development of resistant cultivars is being counteracted by the adaptability of the pathogen.
Late blight on potato:
http://www.sciencedaily.com/images/2007/01/070102132649.jpg (tuber) and
Late blight on tomato:
Microscopy of PLB infected cells:
Late blight fact sheets:
Disease history and background:
Late blight information and resources via:
Recent review of PLB epidemiology and strains in Europe:
_P. infestans_ taxonomy:
Global Initiative on Late Blight:
James Hutton Institute: