Title: Identification of QTL Regions and SSR Markers Associated with Resistance to Reniform Nematode in Gossypium barbadense L. accession GB713 Authors
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 25, 2010
Publication Date: January 1, 2011
Citation: Gutierrez, O., Robinson, A.F., Jenkins, J.N., McCarty Jr., J.C., Wubben, M., Callahan, F.E., Nichols, R.L. 2011. Identification of QTL regions and SSR markers associated with resistance to reniform nematode in Gossypium barbadense L. accession GB713. Theoretical and Applied Genetics. 122:271-280. Interpretive Summary: Interpretive Summary: The reniform nematode is an important pest of Upland cotton in the southern United States; however, there are currently no commercial cultivars resistant to this damaging root parasite. A high level of reniform nematode resistance was found in the Gossypium barbadense accession GB713. To facilitate the transfer of reniform nematode resistance from GB713 to Upland cotton, we endeavored in this study to (1) determine the mode of inheritance of reniform nematode resistance in GB713 and (2) identify molecular markers closely linked to the reniform nematode resistance gene(s) in GB713 that could be used in cotton breeding programs. Our results indicated that one or more genes were involved in the reniform nematode resistance of GB713. We determined that the chromosome 21 SSR markers BNL 1551_162, GH 132_199, BNL 4011_155, and BNL 3279_106 were highly associated with reniform nematode resistance. The chromosome 18 SSR markers BNL1721_178 and BNL 569_131 were also associated with reniform resistance. These SSR markers should be useful in the selection of plants with high levels of reniform nematode resistance derived from GB713.
Technical Abstract: The identification of molecular markers, closely linked to gene(s)in Gossypium barbadense L., accession GB713 that confer a high level of resistance to reniform nematode (RN), Rotylenchulus reniformis Linford & Oliveria, would be very useful in cotton breeding programs. Our objectives were to determine the inheritance of RN resistance in the G. barbadense accession GB713, to identify SSR markers linked with RN resistance QTLs, and to map these linked markers to specific chromosomes. We grew and scored plants for RN reproduction in the P1, P2, F1, F2, BC1P1, and BC1P2 generations from the cross of GB713 × Acala Nem-X. The generation mean analysis using the six generations indicated one or more genes were involved in the RN resistance of GB713. The interspecific F2 population of 300 plants was genotyped with SSR molecular markers that covered most of the chromosomes of cotton. Results showed two QTLs on chromosome 21 and one QTL on chromosome 18. One QTL on chromosome 21 was at map position 168.6 (LOD 28.0), flanked by SSR markers BNL 1551_162 at position 154.2 and GH 132_199 at position 177.3. A second QTL on chromosome 21 was at map position 182.7 (LOD 24.6), flanked by SSR markers BNL 4011_155 at position 180.6 and BNL 3279_106 at position 184.5. Our chromosome 21 map had 61 SSR markers covering 219 cM. One QTL with smaller genetic effects was localized to chromosome 18 at map position 39.6 (LOD 4.0) and flanked by SSR markers BNL 1721_178 at position 27.6 and BNL 569_131 at position 42.9. The two QTLs on chromosome 21 had significant additive and dominance effects which were about equal for each QTL. The QTL on chromosome 18 showed larger additive than dominance effects. Following the precedent set by the naming of the G. longicalyx and G. aridum sources of resistance, we suggest the use of Renbarb1, Renbarb2, and Renbarb3 to designate these QTLs on chromosome 21 at positions 168.6, 182.7, and chromosome 18 at position 39.6, respectively.