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Title: Yield effecgs of two southern leaf blight resistance loci in maize hybrids

Author
item SANTA-CRUZ, JOSE - North Carolina State University
item KUMP, KRISTEN - North Carolina State University
item ARELLANO, CONSUELO - North Carolina State University
item GOODMAN, MAJOR - North Carolina State University
item Krakowsky, Matthew
item Holland, Jim - Jim
item Balint-Kurti, Peter

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2013
Publication Date: 1/5/2014
Citation: Santa-Cruz, J.H., Kump, K.L., Arellano, C., Goodman, M., Krakowsky, M.D., Holland, J.B., Balint Kurti, P.J. 2014. Yield effecgs of two southern leaf blight resistance loci in maize hybrids. Crop Science. 54(3):882-894.

Interpretive Summary: Genes for disease resistance can be found within all diverse plant populations. Why don’t all plants posses the best resistance alleles? Why doesn’t evolution fix these alleles within populations? There are several answers to this question: Some alleles probably are fixed (these are the resistance genes that are not detectable since there is no variation at the locus), Some alleles simply are not selected strongly during evolution due to lack of selection pressure and some resistance alleles may have detrimental effects in the absence of disease. In this study we have looked at two specific resistance genes in maize and asked what their effect is on yield in the presence and absence of disease. It turns out that they have a modest positive yield effect in the presence of disease and, seemingly, a modest yield cost when there is no disease.

Technical Abstract: Plants need to balance resources between yield and defense. This phenomenon has rarely been investigated in the context of naturally-occurring quantitative resistance alleles in an agricultural production environment. B73-3B and B73-6A are two near-isogenic lines (NILs) in the background of the maize inbred B73, each carrying one introgression (called 3B and 6A respectively) encompassing quantitative trait loci (QTL) for southern leaf blight (SLB) resistance . Sets of isohybrid triplets were developed by crossing B73, B73-3B and B73-6A to several inbred lines. A subset of these triplets were selected for which the B73-3B and/or B73-6A hybrid was significantly more SLB resistant than the B73 check hybrid. These selected triplets were examined in multi-environment yield trials including artificially inoculated and disease-free (fungicide-sprayed) conditions. Significant interactions between inoculation treatment and introgressions were detected. In the presence of SLB disease pressure, introgression 3B was associated with an approximately 3% yield increase over B73. Introgression 6A was not associated with a consistent yield advantage in the presence of SLB across all pedigrees but there were significant advantages in specific pedigrees where the 6A resistance phenotype was highly expressed. Results suggested that both introgressions might confer a yield cost in the absence of SLB, but only introgression 6A was associated with a statistically significant yield reduction.