ARS | Publication request: Recombination is suppressed in an alien introgression in peanut harboring Rma, a dominant root-knot nematode resistance gene

Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2010
Publication Date: July 20, 2010
Citation: Nagy, E.D., Chu, Y., Guo, Y., Khanal, S., Tang, S., Li, Y., Dong, W.B., Timper, P., Taylor, C., Ozias-Akins, P., Holbrook Jr, C.C., Beilinson, V., Nielsen, N.C., Stalker, H., Knapp, S.J. 2010. Recombination is suppressed in an alien introgression on chromosome 5A of peanut harboring Rma, a dominant root-knot nematode resistance gene. Molecular Breeding. 26:357-370.

Interpretive Summary: The root-knot nematode causes serious yield losses in peanut. The development of peanut varieties with resistance to this nematode would reduce yield losses while reducing the use of nematicides in fields where these nematodes occur. The identification and refinement of molecular markers for use in marker assisted selection would improve the efficiency of identifying resistant plants, and speed breeding efforts to combine nematode resistance with other important characteristics in peanut. Our research resulted in the development of molecular markers that are reproducible and highly correlated with nematode resistance. These markers are economical to use and can be used in a high-throughput DNA extraction methods. Plant breeders will be able to use these new markers to hasten efforts to combine nematode resistance with other important characteristics in peanut.

Technical Abstract: Rma, a dominant root-knot nematode resistance gene introduced into tetraploid peanut (Arachis hypogaea) from a synthetic allotetraploid donor (TxAG-6), has been widely deployed in modern cultivars. The genomic location and borders of the alien chromosome segment introgressed from TxAG-6 into NemaTAM (a BC7-derived introgression line) and other modern cultivars carrying Rma have not been genetically mapped and resistance gene candidate (RGCs) have not been identified for Rma. Our study focused on densely populating the alien introgression with codominant DNA markers, indentifying and mapping the borders of the alien introgression carried by NemaTAM, and identifying RGCs for Rma. Although, 2,847 simple sequence repeat (SSR) and 380 single strand conformational polymorphism (SSCP) markers were screened for linkage to Rma - 247 of the SSCP markers targeted 202 nucleotide binding site (NBS) leucine rich repeat (LRR) and other resistance ( R) gene homologs (75 were identified by mining a peanut EST database). SSR, NBS-LRR, and Ser/Thr receptor-like kinase loci found in the alien introgression completely cosegregated with Rma in an F4 population (Gregory x Tifguard) and were tightly linked and spanned 3.4 cM in an F5 population (NemaTAM x GP-NC-WS-14). By comparative mapping in the A-genome progenitor of peanut (A. duranensis), Rma was discovered to have been introduced on an interstitial alien chromosome segment spanning one-third to one-half of chromosome 5A. Numerous codominant DNA markers were identified for more finely mapping Rma, shortening the alien introgression harboring Rma by marker assisted selection, and introducing novel root-knot nematode R-genes into peanut by targeting syntenic segments on chromosome 5A and 5B in wild diploid donors.