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Title: Quantitative Trait Loci for Maysin Synthesis in Maize (Zea mays L.) Lines Selected for High Silk Maysin Content

item Guill, Katherine
item Rector, Brian
item Widstrom, Neil
item McMullen, Michael

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2006
Publication Date: 11/1/2006
Citation: Meyer, J., Snook, M., Houchins, K.E., Rector, B.G., Widstrom, N.W., Mcmullen, M.D. 2006. Quantitative Trait Loci for Maysin Synthesis in Maize (Zea mays L.) Lines Selected for High Silk Maysin Content. Journal of Theoretical and Applied Genetics. 115:119-128.

Interpretive Summary: Plant breeders have traditionally used a method known as recurrent selection to improve desirable traits in plant varieties. Recurrent selection involves multiple cycles of selecting the best individuals and recombining genotypes to advance the mean value of the trait. Despite widespread use, little is known about the specific genes affected by recurrent selection. In this study we identify the genes selected in two populations developed by recurrent selection for high maysin levels in corn silks. Our results demonstrate that progress in selection for high maysin was obtained by selection at both regulatory and structural genes. Our results also demonstrate that trait improvement can be made by selection of a limited number of genetic loci. Our findings are significant to plant breeders and geneticists in defining the genetic consequences of selection, indicating a genetic basis of early generation gain as selection on a limited number of important loci.

Technical Abstract: Recurrent selection has been utilized for over a century to increase desired traits in crop plants. One notable trait of interest to plant breeders is insect resistance. Maysin is a naturally occurring C-glycosyl flavone found in maize (Zea mays L.) silk tissue that confers resistance to corn earworm (Helicoverpa zea, Boddie). Recently, two new maize populations were derived for high silk maysin. The two populations were named the EPM (exotic populations of maize) and the SIM (southern inbreds of maize). Quantitative trait locus (QTL) analysis was employed to determine which loci were affected by the selection process in the EPM and SIM populations. The QTL identified included the p (pericarp color) locus, c2 (colorless2), and whp1 (white pollen1). The regulation of whp1 expression in silk tissue is unknown and therefore we analyzed the effect of p and in1 (intensifier1), which has been reported to regulate whp1 expression in aleurone tissue, on whp1 transcript concentration. Through this study we determined that the p locus regulates whp1 transcription and also that recurrent selection increased maysin in these populations by selecting alleles at both structural and regulatory loci.