Abstract only

The identification of new sources of resistance to TTKSK and its related races is necessary to enable the development and deployment of resistant varieties that have race-nonspecific, adult plant resistance (APR) conferred by multiple minor, slow rusting genes. Wheat lines ?Kingbird, ?Kiritati? and ?Juchi? showed high levels of APR to Ug99 races of stem rust fungus when tested in Kenya. The F5 and F6 generation recombinant inbred line (RIL) populations developed from the crosses of moderately susceptible ?PBW343? with the three resistant parents were used in mapping. Field phenotyping of the parents and RILs were conducted at Njoro, Kenya for at least two years with Ug99+Sr24 (TTKST) race under high stem rust pressures. The continuous variation of APR in each RIL population and genetic analyses indicated quantitative nature of resistance that was likely governed by 3 or 4 minor genes. Single and joint year analyses by Inclusive Composite Interval Mapping (ICIM) using informative DArT and/or SSR markers identified consistent APR QTLs on chromosomes 1A, 3BS, 5BL, 7A and 7DS in Kingbird; 2D, 3BS, 5BL and 7DS in Kiritati and 2B, 3BS, 4A, 5BL and 6B in Juchi. QTLs on each genomic regions explained 10- 46% of the phenotypic variation for APR. Pseudo-black chaff phenotype associated with APR gene Sr2 on chromosome 3BS in all six resistant parents and identification of an APR QTL in the same region in all mapping populations confirmed the role of Sr2 in reducing stem rust severity. The QTL on chromosome 7DS in Kingbird was in the same region where pleiotropic APR gene Lr34/Yr18/Pm38 is located. Further studies are underway to saturate the genomic regions harboring new APR QTLs with additional molecular markers.

Genetic Resources Program|Global Wheat Program

English

Lucia Segura

INT2843|INT0610|INT3098

CIMMYT Staff Publications Collection