Cloning of Vgt3, a Major QTL for Flowering Time in Maize

Gaspé Flint, introgression library, plant breeding, stress escape, Zea mays

Flowering time is a complex trait important for crop adaptation to local environments and an essential breeding target to face the challenge of global climate change. A major quantitative trait locus (QTL) for flowering time and number of nodes (ND), qVgt3.05, was previously identified on chromosome 3 in a maize introgression library (IL) derived from the cross B73 x Gaspé Flint (recipient and donor genotypes, respectively. Salvi et al. 2011). In order to clone qVgt3.05, B73 was crossed with its early isogenic line 39-1-2-33 which carries a 17-cM Gaspé Flint introgression on bin 3.05. In this cross qVgt3.05 was placed within 0.3 cM and showed an addictive effect of 1.36 nodes and explained 56.6% of the phenotypic variance. For positional cloning, a total of 7,500 F2 plants were phenotyped and genotyped with SNPs and SSR markers flanking the QTL interval. One-hundred recombinants lines were derived and the QTL was further narrowed the target genomic region to a 380-kb interval. A candidate gene putatively involved in the control of the transition from the vegetative to the reproductive phase of maize was found within this region. We are studying its expression profile and its effect using transgenics. In addition, we are currently testing the presence of genomic structural variations in the Gaspé Flint-originated allele.