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Protecting South Asian Wheat Production from Stem Rust (Ug99) Epidemic
Author(s) -
Sharma Rajiv K.,
Singh Pawan K.,
Joshi Arun K.,
Bhardwaj Subhash C.,
Bains Navtej S.,
Singh Sukhwinder
Publication year - 2013
Publication title -
journal of phytopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 60
eISSN - 1439-0434
pISSN - 0931-1785
DOI - 10.1111/jph.12070
Subject(s) - stem rust , biology , virulence , strain (injury) , puccinia , race (biology) , pathogen , resistance (ecology) , veterinary medicine , microbiology and biotechnology , genetics , gene , agronomy , botany , medicine , mildew , anatomy
The Ug99 group of stem rust races ( P uccinia graminis P ers. f. sp. tritici E riks. & E . H enn.) has evolved and migrated. While the original variant overcame the widely deployed gene S r31 , and S r21 (in C hinese S pring background), but not S r21 in Einkorn, a new strain of Ug99, virulent on S r24, was detected in 2006 and caused a severe epidemic in 2007 in Kenya. Forms virulent on S r36 and S r21 were identified in 2007. Likewise, an Ug99 variant virulent to both S r21 and S r24 was identified in 2008 in K enya. Simultaneously, the original strain spread to Yemen and Sudan in 2006. Fears of a spread into Asia were confirmed when this race was detected in Iran in 2007. This has raised serious concerns that Ug99 could follow the same migratory route from A frica to A sia as Yr9 and cause major epidemics across the epidemiological region of South Asia. In 2005–06, screening in Kenya and Ethiopia of wheat materials from A sian countries revealed a very low frequency of lines resistant to Ug99 and its variants. Under the umbrella of the Borlaug Global Rust Initiative ( BGRI ), significant efforts have been made to counter the challenges posed by Ug99 and its derivative races. Diverse sources of resistance to the pathogen have been identified and incorporated in high‐yielding wheat backgrounds. The most promising strategy has been to deploy spring wheat varieties possessing adult plant resistance ( APR ) in infested and bordering areas to decrease inoculum amounts and slow down the development of new virulence, for example four CIMMYT genotypes with S r2 + have been released in A fghanistan and their seed is also distributed in region bordering Iran. For an immediate remedy, race‐specific resistance genes can be deployed in combinations using marker‐assisted selection. Several Ug99‐resistant varieties have already been released in S outh A sian countries ( A fghanistan, I ndia, N epal, B angladesh and P akistan), and seed dissemination is underway. The Ug99 risk in the region can be reduced to minimum levels by identifying, releasing and providing seed of high‐yielding and resistant cultivars.