Ug99: One Year On

An opportunity here, for me to recap on a post I wrote back in January ’07. Puccinia graminis strain Ug99 has once again hit the headlines and it isn’t good news. The situation in outline is that the Ug99 strain of black rust fungus readily attacks wheat plants, as it resists the most popular rust-resistance genes that are used in modern wheat. It has been steadily spreading northwards from its point of origin in Uganda since 1999 (Uganda and the year 1999 provided the name). Experts were predicting that unless measures were taken, the fungus would find its way into the fertile bread-basket regions of South Asia, via the Arabian peninsula. Potential damage to agriculture in the region was estimated at some 3 billion US dollars per year. In his article  for CAB Reviews, Ravi Singh of the International Maize and Wheat Improvement Center (CIMMYT) highlights the threats of Ug99 migration. Follow this link to download the PDF.

This is still the case but as New Scientist reports, Cyclone Gonu which hit the Arabian peninsula last June could have pushed up the predicted arrival of Ug99 spores in Iran and Pakistan by up to two years. Strong storm winds blew north, not north-west as expected and could have carried airborne rust spores with them. Monitoring of the fungus in Pakistan is reportedly poor, so any such movement might not be apparent straight away.

A further, and more insidious threat comes from the abundance of barberry (Berberis vulgaris)
in Iran. Normally, growing on wheat, the fungus reproduces asexually
and produces genetically identical spores. The life-cycle of Puccinia graminis
is such that on a compatible intermediate host like barberry, it can
undergo sexual reproduction and acquire genes from other rust strains.
New strains could be produced that pose even more severe problems for
wheat growers.

Wheat breeding efforts are underway, but they are slow and may take
five years or more to produce Ug99-resistant varieties and to establish
them in the path of the fungus’ spread. Hopefully this has given you a
taste of the issues surrounding Puccinia graminis Ug99 and as always when you want to research the topic further, your best guide to the scientific literature in this field is CAB Abstracts.

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