CHARACTERIZATION OF HOST-PATHOGEN INTERACTIONS IN BARLEY AND WHEAT
Location: Cereal Crops Research
Title: A region of barley chromosome 6H harbors multiple major genes associated with net type blotch resistance.
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 30, 2008
Publication Date: September 1, 2008
Citation: Abu, Q.M., Liu, Z., Faris, J.D., Chao, S., Edwards, M.C., Lai, Z., Franckowiak, J.D., Friesen, T.L. 2008. A region of barley chromosome 6H harbors multiple major genes associated with net type blotch resistance. Theoretical and Applied Genetics. 117:1261-1270
Interpretive Summary: Net type net blotch is one of the most destructive disease of barley in the US and worldwide. In this research, we have identified and partially characterized the effects of two genes responsible for resistance to the pathogen causing this disease. Two different pathotypes of the pathogen were used to identify two distinct but closely linked genes that were mapped to barley chromosome 6H close to the centromere. Molecular markers were identified that will be useful to barley breeders for marker-assisted selection of these genes when introgressing into barley cultivars.
Net type of net blotch (NTNB) on barley, caused by Pyrenophora teres f. teres Drechs. is prevalent in barley growing regions worldwide and is particularly damaging under cool, wet conditions. A population of 118 doubled haploid (DH) lines developed from a cross between barley cultivars ‘Rika’ and ‘Kombar’ was used to evaluate resistance to NTNB due to their differential reaction to various isolates of P. teres f. teres. Rika was resistant to P. teres f. teres isolate 15A and susceptible to isolate 6A. Conversely, Kombar was resistant to 6A, but susceptible to 15A. A progeny isolate of a 15A × 6A cross identified as 15A×6A#4, which was virulent on both parental lines, was also used to evaluate the Rika/Kombar (RK) population. The RK DH population was evaluated for disease reactions to the three isolates. Isolate 15A induced a resistant: susceptible ratio of 78:40 (R: S) whereas isolate 6A induced a resistant: susceptible ratio of 40:78. All but two lines had opposite disease reactions indicating two major resistance genes linked in repulsion. Progeny isolate15A×6A#4 showed a resistant: susceptible ratio of 1:117 with the one resistant line also being the single line that was resistant to both 15A and 6A. Deviation from expected segregation ratios in the DH population was due to segregation distortion. An RK F2 population segregated in a 1:3 (R: S) ratio for both 15A and 6A indicating that resistance is recessive. Simple sequence repeat (SSR), sequence tagged site (STS), cleavage amplified polymorphism (CAP), and restriction fragment length polymorphism (RFLP) markers were used to identify a region on chromosome 6H associated with NTNB resistance in the RK DH population.
Key words: NTNB, segregation distortion, and Drechslera teres.