A genetic linkage map of a flint maize (Zea mays var.indurata L.) italian landrace using a one-way pseudo testcross strategy and multilocus PCR-based markers.

We have used for the first time in maize a one-way pseudo-testcross mapping strategy in combination with different types of multi-locus PCR-based markers (RAPD, ISSR, AFLP, SAMPL) to construct a saturated genetic linkage map of the Italian flint maize (Z. mays var. indurata L.) landrace ‘Nostrano di Storo’. This mapping strategy was compared with the traditional backcross one and SSR loci selected from Maize Genome Database were also assayed to associate linkage groups to those known from published map and to orient linkage groups or specific chromosome arms. A total of 326 markers, comprising 8 RAPD, 7 I-SSR, 259 AFLP, 28 SAMPL, 24 SSR, were scored in 64 F1 individuals obtained from a cross between a highly heterozygous genotype of the landrace with the inbred line B37. Grouping of the markers at a LOD score of 5.0 resulted in 10 linkage groups and a framework map covering 1826 cM was assembled by using 282 markers that could be ordered with a LOD threshold of 2.5. The efficiency of pseudo-testcross strategy was concluded to be around twice compared to that of backcross because of its higher ability to detect the recombination events occurring between pairs of linked loci. Of the total markers, 12.5% showed segregation distortion in the F1 population, whereas in the BC1 the distortion was evident for 18.5% of loci. The results are discussed in terms of map use as a tool for characterizing the Italian maize germplasm and designing an appropriate conservation.