Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 26, 2003
Publication Date: November 1, 2003
Citation: Flint-Garcia, S.A., Darrah, L.L., McMullen, M.D., Hibbard, B.E. 2003. Phenotypic vs marker assisted selection for stalk strength and second generation european corn borer resistance in maize. Theoretical and Applied Genetics. 107(7):1331-1336. Interpretive Summary: Stalk lodging in corn, the breakage of the corn stalk at or below the ear resulting in the loss of the ear at harvest, causes significant losses each year in the United States. An insect pest that increases stalk lodging through stalk tunneling is the European corn borer. Traditional breeding methods have been successful in developing germplasm with better stalk strength and resistance to European corn borer, but require many field seasons for selection. Previous studies have identified gene regions with corresponding genetic markers that may be responsible for stalk strength and resistance to the European corn borer. The objective of this study was to compare selection based on traditional breeding methods to selection based on genetic markers. We found that in selecting for stalk strength, both methods of selection were adequate, although the traditional breeding method typically gave better results. For stalk strength, traditional breeding is faster and less expensive than the genetic marker method. In selecting for resistance to the European corn borer, we found that using the genetic marker data often gave better results than the traditional method. For European corn borer resistance, the genetic marker method may be more cost effective and require less labor. This information will be important to corn breeders and other researchers in their attempts to increase stalk strength and resistance to the European corn borer. The results of this study allow them to choose which selection method may be the fastest and/or most cost effective.
Technical Abstract: Maize (Zea mays L.) stalk lodging is breakage of the stalk at or below the ear, which may result in loss of the ear at harvest. Stalk lodging is often intensified by the stalk tunneling action of the second-generation of the European corn borer (2-ECB) (Ostrinia nubilalis (Hubner)). Rind penetrometer resistance (RPR) has been used to measure stalk strength and improve stalk lodging resistance, and quantitative trait loci (QTL) have been identified for both RPR and 2-ECB damage. Phenotypic recurrent selection (PS) increases the frequency of favorable alleles over cycles of selection. Several studies have indicated that marker-assisted selection (MAS) is also a potentially valuable selection tool. The objective of this study was to compare the efficiency of PS vs. MAS for RPR and 2-ECB. Marker-assisted selection for high and low RPR was effective in the three populations studied. Phenotypic selection for both high and low RPR was more effective than MAS in two of the populations. However, in a third population, MAS for high RPR using QTL effects from the same population was more effective than PS, and using QTL effects from an independent population was just as effective as PS. Marker-assisted selection for resistance and susceptibility to 2-ECB using QTL effects from the same population was effective in increasing susceptibility, but not in increasing resistance. Marker-assisted selection using QTL effects from an independent population was effective in both directions of selection. Thus, MAS was effective in selecting for both resistance and susceptibility to 2-ECB. These results demonstrated that MAS can be an effective selection tool for both RPR and 2-ECB resistance. These results also validate the locations and effects of QTL for RPR and 2 ECB resistance identified in earlier studies.