Genetic Analysis of Southern Leaf Blight, Gray Leaf Spot, and Northern Leaf Blight Resistance Using Near-Isogenic Lines and Mapping Populations in Maize
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2008-12-05
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Abstract
Quantitative disease resistance (QDR) is important in maize; however very little is known about the molecular genetic basis of QDR. Southern leaf blight (SLB), gray leaf spot (GLS), and northern leaf blight (NLB) are three important foliar diseases impacting maize production. The objective of this research was to map SLB, GLS, and NLB disease resistance quantitative trait loci (dQTL).
Genetic dissection of quantitative resistance to SLB was performed using B73 near-isogenic lines (NILs). B73 is a historically important maize line with excellent yield potential but high susceptibility to all three of these foliar diseases. NC292 and NC330 are B73 NILs that are highly resistant to SLB. They were derived by repeated backcrossing of an elite source of SLB resistance (NC250P) to B73, with selection for SLB resistance among and within backcross families. The goals were 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 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. 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.
The goals of the second project were to generate and evaluate NILs with different subsets of the NC250P introgressions present in NC292 and NC330 and to determine the effects of specific introgressions or introgression combinations on SLB resistance in juvenile and adult maize plants. Of the 12 NC250P introgressions identified, lines containing introgressions 3B, 6A, and 9B (bins 3.03-3.04, 6.01, and 9.02-9.03) were all significantly more resistant to SLB than B73 in the field trials. The two introgressions that provided the majority of the adult plant SLB resistance in NC292 and NC330 were introgressions 3B and 6A. Introgression 6A was the only introgression that had a significant effect (P < 0.0001) on juvenile plant resistance. Introgression 6A not only had the most significant effect on SLB resistance in juvenile plants, but it also provided the largest magnitude of effect on SLB resistance in adult plants.
The objectives of the third study were to identify SLB, GLS and NLB (dQTL) in a maize recombinant inbred line (RIL) population, and to determine if evidence for multiple disease resistance (MDR) exists in the population. The RIL population used in this study was derived from a cross between maize lines Ki14 and B73 (KB population). Nine, eight, and six dQTL were identified for SLB, GLS, and NLB, respectively. dQTL for the three diseases colocalized in bin 1.06, while dQTL colocalizing for two of the three diseases were identified in bins 1.08-1.09, 3.04, 8.05, and 10.05. Highly significant correlations were found between the resistances to the three diseases. The highest correlation was between SLB and GLS, with a correlation coefficient of 0.62. Our results demonstrate that some of the genes conferring resistance to more than one of these diseases, suggesting that MDR genes segregate within the KB population.
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Southern leaf blight, gray leaf spot, northern leaf blight, quantitative disease resistance, multiple disease resistance, disease resistance quantitative trail loci, near-isogenic lines, maize, recombinant inbred lines
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PhD
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Crop Science
