Having dedicated the better part of 2009 to understanding the threat posed by Ug99, a fungus that threatens to decimate much of the Eastern Hemisphere’s wheat crop, our ears always prick up when we hear of looming agricultural catastrophes. The latest comes in the form of Pathogen206, which afflicts wheat with yellow rust (aka stripe rust). Like Ug99, the emerging pathogen overcomes one of mankind’s key genetic defenses—a gene in which we seemingly placed far too much trust:
Following the epidemics associated with the development of virulence for Yr9, stripe rust susceptible cultivars were in most cases replaced. Unfortunately the resistance of many of the replacement cultivars, including the mega-cultivars PBW343, Inquilab-91, Chamran, Shiroudi, Kubsa, and Imam, was based on the single major gene Yr27 only. These cultivars represent the same genetic material (Atilla) released under different names in respective countries.
The breakdown of Yr27 was first reported in South Asia between 2002-2004, with mega-cultivars like PBW343 and Inquilab-91 in India and Pakistan showing susceptibility to the new Yr27 virulent pathotype(s). Replacement of these cultivars is underway (e.g, Inquilab-91 in Pakistan is being replaced by new resistant cultivars like Seher-06). Unfavourable environmental conditions presumably restricted the increase in frequency and distribution of pathotypes within the Yr27 lineage until 2009, when favourable conditions resulted in serious outbreaks of stripe rust in several countries e.g., Morocco, Uzbekistan, Turkey, Azerbaijan, Algeria and Afghanistan. Virulence for Yr27 was confirmed in many of the 2009 outbreaks.
Climactic conditions are currently ideal for a widespread epidemic, which could take out much of the Middle East’s wheat in just two weeks. (The current 2010 spread is shown in the map above.) The good news is that there are proven alternatives to the Yr27 wheat that has been breached; the bad news, per the usual, is that getting this wheat planted requires cooperation from dysfunctional national governments. Color us a deep shade of pessimistic on this one.