Criolla×Bienal

The F2 population was derived from a self-pollinated individual F1 plant from the intercross between the annual cultivar ‘Criolla INTA’ and ‘Bienal’, a petaloid male sterile biennial carrot from INTA’s (Instituto Nacional de Tecnología Agropecuaria) breeding program. ‘Criolla INTA’ often restores fertility to cytoplasmic male-sterility (CMS) hybrids, so one of several male fertile F1 plants was identified and an F2 population was generated by self-pollination. Flowering and sterile:fertile plant segregation in the F2 population were noted. Both parental stocks, as well as the F2 population including 280 and 297 plants, were direct seeded in the field at La Consulta, Mendoza, Argentina (lat. 33°320S, long. 69°040W) on 4 May 2005 and 8 May 2006, respectively.

Linkage analysis and map construction were conducted using JoinMap version 3.0. Linked loci were grouped using a LOD threshold of 4–7 and a maximum recombination fraction of 0.4. Map distances in centiMorgans (cM) were calculated using the Kosambi mapping function.

Most of the parental allelic phase was ambiguous or unknown, so in a first approach all dominant markers were scored as coming from the same parent and codominant markers were scored as two dominant markers arbitrarily named A and B (e.g. gssr46A and gssr46B). This analysis gave us pairs of linkage groups, with each pair identified by their codominant markers. For a given pair, the parental allelic phase was determined for each group of markers and codominant markers. This new scoring matrix was analyzed with JoinMap for final map construction.

A map of 355 markers was grouped in 9 linkage groups with LOD scores between 4 and 7. The total map length was 669 cM with an average marker-to-marker distance of 1.88 cM. The number of markers per linkage group ranged from 26 to 51 with an average of 39 markers per linkage group.