Submitted to: American Phytopathological Society
Publication Type: Abstract Only
Publication Acceptance Date: June 18, 2012
Publication Date: August 12, 2012
Citation: Wang, C., Ulloa, M., Roberts, P.A. 2012. QTL analysis for transgressive resistance to root-knot nematode in a cotton RIL population derived from interspecific susceptible parents. [abstract] In Proceedings of American Phytopathological Society and International Plant Protection Congress Joint Meeting, August 1 to 6, 2012, Honolulu, Hawaii. p. 693.
The root-knot nematode (RKN, Meloidogyne incognita) resistance gene rkn1 in Gossypium hirsutum Acala NemX interacts with a transgressive factor RKN2 from susceptible G. barbadense Pima S-7 to produce high resistance to RKN. The rkn1 and RKN2 genes are clustered and linked to SSR markers CIR316 and MUCS088, which are located on the telomeric region of chromosome (Chr) 11. QTL analysis on an F2:7 (Pima S-7 x Acala NemX) population validated the importance of this telomeric region, which contributed to resistance to both root-galling and nematode egg production. Of 48 SSR markers screened from Chr11, 29 SSRs amplified products located on homoeologous Chr21 with different size-alleles from those on Chr11. Marker allele-sizes were used to extract BAC clones from pools and super pools of Acala N901 (Acala NemX background) library. Preliminary blast analysis and sequence composition of 48 marker and 48 assembled BAC sequenced-clones of Acala N901 associated with the telomeric RKN resistance region indicated the existence of many copies of resistance gene analogs (RGA). One of the RGA sequences (CIR316_222) had 32 percent identity to a potato late blight putative resistance RGA1 gene. In addition, CIR316_222 (3148 bp) on Chr11 had 83 percent identity with another RGA of CIR316_214 (3375 bp) on Chr21. When CIR316_222 and CIR316_214 sequences were compared with the corresponding region of the D5 G. raimondii genome sequence, the D5 sequence shared 88 percent identity with Chr11 and 92 percent identity with the RGA on Chr21. These sequence comparisons provide further insight into the organization and molecular evolution of the RKN-resistance gene cluster on Chr11 and its homoeolog Chr21.