Mapping Vrn, the gene controlling vernalization requirement in carrot

ALESSANDRO, M.S.; GALMARINI, C.R.; ALI, A; SIMON, P.W.

Anaheim

Congreso; 33rd International Carrot Conference.; 2009

University of California

Carrot (Daucus carota L.) is a cool-season vegetable normally classified as a biennial or winter annual species, requiring vernalization to induce flowering. Nevertheless, some cultivars adapted to warmer climates require less vernalization and can be classified as early-flowering or annual. Previous progeny evaluation of crosses between early- (Criolla INTA) and late-flowering (biennial lines from  INTA breeding program) cultivars showed that F1 were completely annual and observed segregation ratios in F2 and BC1 families were not significantly different from expected segregation ratios under the hypothesis of a single dominant gene conditioning the annual habit, which we call Vrn. The objective of the present work was to localize the genomic region that controls vernalization response in carrot. We evaluated an F2 progeny, derived from the intercross between 'Criolla INTA' and a biennial carrot, in a two year trial at La Consulta. 280 and 297 plants were sown each year, once per week plants were evaluated. Individual plants were scored as being vegetative until the first floral internode elongated. Percentages of flowering F2 plants were 73.0% and 72.7% each year. DNA from 125 F2 plants was extracted. To construct the linkage map 310 SSR, 145 RAPD and 8 SCAR markers were screened in the population. Also the AFLP technique was used with EcoRI and MseI as digestion enzymes. We obtained 293 polymorphic markers for the population: 27 SSR (22 codominant), 30 RAPD, 1 SCAR (codominant) and 212 AFLP. Molecular and phenotypic data were analyzed with the JoinMap3.0 program to map the flowering gene.