Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2006
Publication Date: 8/8/2006
Citation: Krakowsky, M.D., Lee, M., Garay, L., Woodman-Clikeman, W., Long, M.J., Sharopova, N., Frame, B., Wang, K. 2006. Quantitative trait loci for callus initiation in maize (Zea mays l.). Journal of Theoretical and Applied Genetics 113:821-830. Interpretive Summary: This research was conducted expand our understanding of the genetics of corn plant regeneration under tissue culture. Most agronomically useful corn germplasm does not have the ability to regenerate in tissue culture, so less desirable germplasm must be used for plant transformation procedures. The time and resources needed recover agronomically useful maize germplasm from this process could be greatly reduced if the ability to regenerate plants in tissue could be transferred into the desirable germplasm. To this end, we must first understand which genes control the trait of interest. Several locations on corn chromosomes that are associated with regenerability have been identified in this study. Many of these locations are also associated with genes involved in the production of abscisic acid, a hormone related to plant response to stress. The results of this experiment are important because they can allow scientists, through crosses between regenerable and non-regenerable corn lines, to select maize plants with improved ability to regenerate in tissue culture systems. This will reduce the resources necessary for plant transformation procedures.
Technical Abstract: Induction of embryogenic callus in culture is an important step in plant transformation procedures, but response is genotype specific and the genetics of the trait are not well understood. Quantitative trait loci (QTL) were mapped in a set of 126 recombinant inbred lines (RILs) of inbred H99 (high Type I callus response) by inbred Mo17 (low Type I callus response) that were evaluated over two years for Type I callus response. QTL were observed in a total of eleven bins on eight chromosomes, including eight QTL with main effects and three epistatic interactions. Many of the QTL were mapped to the same or bordering chromosomal bins as candidate genes for abscisic acid metabolism, indicating a possible role for the hormone in the induction of embryogenic callus, as has previously been indicated in microspore embryo induction. Further examinations of allelic variability for known candidate genes located near the observed QTL could be useful for increasing the understanding of the genetic basis of induction embryogenic callus. The QTL observed herein could also be used in a marker assisted selection (MAS) program to improve the response of agronomically useful inbreds, but only if the resources required for MAS are lower than those required for phenotypic selection.