May 30th, 2016: Race Analysis Data from 2015 Indicates a Possible Shift in Stem Rust Populations in East Africa


Digalu crop destroyed by race TKTTF. Ethiopia 2013

Race analysis undertaken by EIAR, Ambo, GRRC, Denmark and USDA-ARS CDL on samples collected in 2015 from Ethiopia and Kenya indicates that stem rust populations in East Africa are changing. The detection of race TKTTF (“Digalu” race) in Ethiopia in 2012 and the subsequent epidemics in 2013, 2014 and 2015 (see Olivera et al 2015) appears to have profoundly influenced the stem rust populations in East Africa. For over a decade the Ug99 race group has dominated in both Ethiopia and Kenya, however the latest results indicate that this situation is now changing.

A total of 214 stem rust samples from Ethiopia in 2015 were analysed by the 3 different laboratories. The results indicated that the original Digalu race (TKTTF) dominated throughout the country, with 86% (n=185) of samples being this race. Other presumed variants of the Digalu race were also detected – TTTTF (n=9), TTTTC (n=3), TRTTF (n=3), PKPTF (n=4), PKPTC (n=2), PTTTF (n=1), PTPTF (n=1). Other races included: SJPQC (n=1), JRCSF (n=1), JRCQC (n=1). Ug99 (race TTKSK) was still present at very low frequency, only 2 samples out of 214.

In Kenya, only 17 isolates were analysed by USDA-ARS CDL however the results indicated that the Digalu group of races were also emerging. A total of 7 races were identified in Kenya. Races presumed to be variants of the Digalu race pre-dominated. The most frequent race was PTTTF (n=7), with PKPTC (n=3) and PKPTF (n=1) also detected. Interestingly, the original Digalu race (TKTTF) was not detected in the Kenya samples. Three Ug99 races were also detected in the Kenya 2015 samples: Races TTKSK (n=4), TTKTT (n=1) and TTKTT (n=1).

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