ARS | Publication request: Sheath-blight resistance QTLs and in japonica rice germplasm

Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 7, 2011
Publication Date: July 22, 2011
Citation: Nelson, J., Oard, J.H., Groth, D., Utomo, H., Jia, Y., Liu, G., Moldenhauer, K.K., Correa-Victoria, F.J., Fjellstrom, R.G., Scheffler, B.E., Prado, G.A. 2011. Sheath-blight resistance QTLs and in japonica rice germplasm. Euphytica. 184:23-24.

Interpretive Summary: Sheath blight disease caused by the soil-borne nectrotrophic pathogen Rhizotonia solani has been a major constraint for rice productions worldwide. In the present study, sheath blight resistance (SBR)-QTLs were identified in a US japonica breeding material MCR10277. A doubled- haploid population involving MCR10277 was evaluated under field and greenhouse conditions with southern U. S. and Colombian pathogen isolates and genotyped at 111 microsatellite marker loci. A total of four SBR-QTLs from MCR10277 were identified, together accounting for 47% of field genetic variation. Among SBR-QTLs is a chromosome-9 QTL, qsbr_9.1, lying at a genetic map location previously repeatedly identified in indica and japonica material. Other QTLs were predicted to interact with plant developmental genes raising a need for further investigation. In additional, two QTLs were demonstrated to contribute differential resistance to the isolates from the Colombia and southern US. Identification of the major SBR QTLs qsbr_9.1 from MCR10277 offers promises for stable resistance and gene isolation.

Technical Abstract: Sheath blight (SB), caused by Rhizoctonia solani, is one of the most serious diseases of cultivated rice (Oryza sativa L.) and genetic resistance is in demand by rice breeders. With the goal of resistance-QTL discovery in U. S. japonica breeding material, a set of 197 F1 doubled-haploid lines (DHLs) from a cross between MCR10277 (resistant) and Cocodrie (susceptible) were evaluated in field and greenhouse assays with southern U. S. and Colombian pathogen isolates and genotyped at 111 microsatellite marker loci. Four SB resistance (SBR) QTLs from MCR10277 were identified, together accounting for 47% of field genetic variation after resistance effects of plant height and heading time were accounted for. In all trials the strongest effect was provided by a chromosome-9 QTL, qsbr_9.1, lying at a genetic map location repeatedly implicated previously in SB resistance in both indica and japonica material and probably inherited from cultivar Teqing. Though two SB-associated QTLs coinciding with height or heading-time loci were rejected as true SBR QTLs, other major height or heading-time loci showed no influence on SBR, suggesting that the connection between plant developmental gene action and the course of SB infection is not simple. Two QTLs for resistance to the U. S. R. solani isolates were ineffective against a Colombian isolate, whereas for the U. S. pathogen isolate a microchamber greenhouse assay revealed the same QTLs as did field inoculation. These SBR QTLs from MCR10277, especially the well-supported chromosome-9 QTL, offer promise as a breeding target for stable resistance.