Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2008
Publication Date: 3/1/2009
Citation: Zwonitzer, J.C., Bubeck, D.M., Bhattramakki, D., Goodman, M.M., Arellano, C., Balint Kurti, P.J. 2009. Use of backcross recurrent selection and QTL mapping to identify loci contributing to southern leaf blight resistance in a highly resistant maize line. Theoretical and Applied Genetics. 118:911-925. Interpretive Summary: NC292 and NC330 are two maize lines that are genetically extremely similar to the commonly used line B73. However, they are much more resistant to the disease Southern leaf blight. Int his paper we identify the genetic factors responsible for this difference.
Technical Abstract: B73 is a commonly used maize line with excellent yield potential but high susceptibility to the foliar disease southern leaf blight (SLB). NC292 and NC330 are B73 near-isogenic lines (NILs) that are highly resistant to SLB. They were derived by repeated backcrossing an elite source of SLB resistance (NC250P) to B73, with selection for SLB resistance among and within backcross families. The goal of this paper was to characterize the loci responsible for the increased SLB resistance of NC292 and NC330 and to determine how many of the SLB disease resistance quantitative trait loci (dQTL) were selected for in the development of NC292 and NC330. Genomic regions that differentiated NC292 and NC330 from B73 and which may contribute to NC292 and NC330’s enhanced SLB resistance were identified. Ten NC250P-derived introgressions were identified in both the NC292 and NC330 genomes of which eight were shared between genomes. dQTL were mapped in two F2:3 populations derived from lines very closely related to the original parents of NC292 and NC330—(B73rhm1 x NC250A and NC250A x B73). Nine SLB dQTL were mapped in the combined populations using combined SLB disease data over all locations (SLB AllLocs). Of these, four dQTL precisely colocalized with NC250P introgressions in bins 2.05-2.06, 3.03, 6.01, and 9.02 and three were identified near NC250P introgressions in bins 1.09, 5.05-5.06, and 10.03. Therefore the breeding program used to develop NC292 and NC330 was highly effective in selecting for multiple SLB resistance alleles.