Abstract only

Utilization of stem rust resistance genes in breeding programs resulted in effective control of stem rust in most countries during the second half of the 20thcentury. However, the detection of stem rust race Ug99 in East Africa in 1998, a Pgt race with broad virulence, and adaptive capacity, and frequent stepwise mutations to new strains, indicated that continued efforts were necessary to control the disease. This study was aimed at evaluating the effectiveness of quantitative resistance in reducing the susceptibility of wheat in case a major gene breaks down during the onset of a new virulent race. In 2005 a trial was set to evaluate the effectiveness of Sr24 in controlling Ug99. The trial consisted of wheat lines with Sr24±Sr2, and was carried out for four seasons; viz. 2005, 2006 and 2 seasons in 2007. During the first two seasons, Sr24 gene was very effective conferring a near immune response. In the last season of 2007 a new race identified as TTKST and virulent to Sr24 appeared in Kenya. The results indicated that lines combining Sr24 and Sr2 remained resistant whereas those lacking Sr2 were susceptible scoring up to 90S. These results imply that deployment of quantitative disease resistant enes in a major gene resistance background may safeguard wheat from an epidemic in case of evolution of a virulent race like TTKST. Breeding to incorporate both major and minor genes may increase durability.

Global Wheat Program

English

Lucia Segura

INT2843|INT0610