Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 2.34

Development of an introgression MAIZE library of the early-flowering variety Gaspé Flint into B73

S. Salvi, C. Buonfiglioli, M. Bellotti, S. Vecchi, E. Govoni, R. Tuberosa

Department of Agroenviromental Sciences and Technology, University of Bologna, Via Fanin 44, 40137 Bologna, Italy

maize, flowering time, QTL, Nearly Isogenic Lines

An introgression library (IL) is a collection of lines each carrying a molecular marker-defined chromosome segment introgressed from a (usually) agriculturally unadapted accession into the genetic background of an elite line (Zamir, 2001, Nat. Rev. Genet. 2: 983-989). The collection has the unadapted accession genome entirely represented among the set of IL lines. Because of their genetic make-up, ILs are ideal tools for mapping and analysing complex traits. Within ILs, multiple QTLs are segregated in single homozygous lines, where can be analysed in an adapted genetic background with epistatic effect reduced to a minimum. IL lines have also the potentiality to directly serve as pre-breeding or breeding material.

Adapting the duration of the cultivation period of a crop to a specific environment is a major target of plant breeding. This is particularly true for maize, a crop of tropical origin now cultivated over a wide range of growing environments. In the cultivated maize germplasm, flowering time is quantitatively inherited and thus amenable to QTL analysis. The aim of this research is to produce a collection of maize IL lines with the genome of the extremely early-flowering variety Gaspé Flint introgressed into the elite genetic background of the medium-late line B73. Among the ILs collection in the B73 background, the Gaspé Flint genome will be fully represented and, therefore, a dissection of the genetic components controlling the large difference in flowering time will be possible. Based on trait differences between the donor and the recipient genotypes, the IL collection will also serve as a permanent source of nearly isogenic material for QTL analysis and cloning for many other morpho-physiological traits, such as plant height, number of nodes and tiller, leaf area, root architecture, yield and yield components (i.e. number and size of kernel, number of ears), heterosis, etc. Specific marker-delimitated chromosome segments could also be utilized in marker-assisted selection programmes. The IL collection is being produced by a molecular marker-assisted backcross based on publicly available SSR markers. The average Gaspé Flint introgressed segment length is 20-30 cM; this will allow for the production of ca. 70-80 IL lines covering the maize genome. A genetic map based on the first generation of assisted backcross will be presented. Interestingly, preliminary QTL analysis showed that a major QTL for flowering time and number of nodes maps on chromosome 8 bin 8.05, where QTLs for flowering time and related traits have also been identified in a large number of mapping populations (Salvi et al., 2002, Plant Mol. Biol. 48: 601-613).