|GASORE, ELIE - University Of Arkansas|
|PRASAD, BISHWAJIT - University Of Arkansas|
Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2015
Publication Date: 6/3/2015
Citation: Eizenga, G.C., Jia, M.H., Pinson, S.R., Gasore, E.R., Prasad, B. 2015. Exploring sheath blight quantitative trait loci in a Lemont/O. meridionalis advanced backcross population. Molecular Breeding. 35(6):140. doi:10.1007/s11032-015-0332-3.
Interpretive Summary: Sheath blight is one of the most prevalent fungal diseases of cultivated rice and causes significant economic damage to rice production worldwide. No source of complete resistance to sheath blight disease has been identified in cultivated rice (Oryza sativa). The wild Oryza species, which are closely related to cultivated rice, are a potential source of important traits including new resistance genes to fight pests like sheath blight disease. O. meridionalis is the wild Oryza species endemic to Australia and can be successfully crossed with cultivated rice. The objective of this research was to identify the chromosomal location(s) of possible sheath blight resistance gene(s) in an O. meridionalis accession that previously demonstrated moderate resistance to sheath blight disease in greenhouse studies. In this study, we began the process of identifying these potential resistance genes and transferring them into the popular southern U.S. long grain variety, Lemont, which is very susceptible to sheath blight disease. One major chromosomal region was identified associated with the potential sheath blight resistance gene(s) contributed from the O. meridionalis parent. This region was previously identified in cultivated rice but O. meridionalis may have a different sheath blight resistance gene because it diverged from cultivated rice early in evolutionary time. Efforts are underway to continue incorporating this potential sheath blight resistance gene into Lemont and develop adapted, resistant lines available to rice breeders for use in the development of new rice varieties with superior resistance for the U.S. rice industry.
Technical Abstract: Oryza meridionalis is the wild Oryza species endemic to Australia. There are eight AA genome Oryza species, one of which is cultivated rice, O. sativa and O. meridionalis is the most diverged of the eight species. An O. eridionalis (IRGC105608) accession was identified as being moderately resistant to rice sheath blight disease and used as the donor parent to develop an advanced backcross population with the U.S. semi-dwarf rice cultivar, Lemont, as the recurrent parent. The population was genotyped with 113 markers, 112 SSR and one SNP, and the linkage map spanned 1234.5 cM. Sheath blight (ShB) disease was evaluated in both greenhouse and field conditions. Days to heading (DH), plant height (PH), and culm angle (CA), factors that can confound sheath blight disease ratings under field conditions, were recorded. Multiple interval mapping identified qShB9 as the most significant ShB-QTL in all trials with resistance to sheath blight disease attributed to the O. meridionalis parent in all cases. No QTL for any of the potential confounding traits was identified in this region of chromosome 9 in this cross. Lemont was found to contribute the desirable alleles that decreased the days to heading on chromosome 8 and plant height on chromosome 1, in part due to the semi-dwarf gene, sd1, for short plant stature. No CA-QTL was identified due to the lack of segregation for this trait, especially in the advanced backcross generations.