Title: Serious Outbreaks of Wheat Stripe or Yellow Rust in Central and West Asia and North Africa – March/April 2010

Wheat is the primary staple cereal crop throughout the CWANA region, grown on over 50 million hectares. The region has the highest per capita consumption of wheat in the world. Wheat rusts are the main economically damaging diseases of wheat, with periodic epidemics recorded in recent decades in the CWANA region. The breakdown of resistance gene Yr9 in the 1980’s resulted in damaging stripe or yellow rust epidemics in several countries in East Africa, the Near East and West/South Asia, in which cultivars carrying this gene had come to dominate.


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.


Conditions favouring rust development have continued into 2010, with mild winters and adequate rainfall in several CWANA countries resulting in early outbreaks of stripe rust. The susceptible response of cultivars known to carry Yr27 is consistent with the widespread presence of virulence for Yr27 in new areas. Since early March, reports of serious outbreaks of stripe rust have been received from Syria, Iraq, Turkey, Azerbaijan, Uzbekistan, Morocco, and Lebanon (see map). Stripe rust incidences have also been observed, on susceptible cultivars, in the Northern, Southern and Western part of Iran, and farmers have taken necessary management measures and sprayed fungicide to control the disease. Given the widespread presence of susceptible cultivars and continuing favourable environmental conditions, further spread and development of stripe rust is likely. Regional monitoring of pathogen variability and disease development must be undertaken as a matter of high priority and timely control measures such as chemical intervention might need to be considered in certain areas. Resistant varieties (existing) and experimental materials in the national trials resistant to stripe rust must be urgently promoted through special emphasis on seed production to reduce future epidemics.


Reporting of new outbreaks to Borlaug Global Rust Initiative (BGRI) staff, K. Nazari (ICARDA) k.nazari@cgiar.org and D. Hodson (FAO) David.Hodson@fao.org is encouraged. Pathotype analysis of representative samples of stripe rust would provide additional information about which sources of resistances in wheat may be at particular risk. The Global Rust Reference Centre in Denmark may undertake such analysis, but only on a limited number of samples. Please contact K Nazari or D. Hodson for essential sampling and dispatching procedures.


Approximate Locations of Outbreaks of Wheat Stripe Rust Reported March-April 2010



Authors: David Hodson and Kumarse Nazari


Disclaimer
The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Borlaug Global Rust Initiative (BGRI) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.



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newsroom170: Serious Outbreaks of Wheat Stripe or Yellow Rust in Central and West Asia and North Africa – March/April 2010
Article: Pathogen206 (permalink)
Categories: :Pathogen:Surveillance, :Pathogen:Featured Content
Date: April 28, 2010; 10:57:08 AM EDT
Author Name: John Bakum
Author ID: John