Comparative mapping of QTLs determining the plant size of Brassica oleracea

Quantitative trait loci (QTLs) influencing the size of leaves and stems wer e detected by restriction fragment length polymorphisms (RFLP) in three Bra ssica oleracea F-2 populations derived from crosses of rapid-cycling Brassi ca to three B. oleracea varieties, Cantanese, Pusa Katki and Bugh Kana. Mor phological traits, including lamina length, lamina width, petiole length, s tem length, stem width and node number were evaluated. A total of 47 QTLs w ere detected based on a LOD threshold of 2.5. Through comparative mapping w e inferred that the 47 QTLs might reflect variation in as few as 35 differe nt genetic loci, and 28 ancestral genes. For the trait of lamina length, we identified QTLs corresponding to five ancestral genes, which mapped near t he locations corresponding to five known Arabidopsis mutations, rev, axr1, axr3, axr4 and as2. For the trait of stem length, we identified QTLs corres ponding to five ancestral genes, which mapped near the locations correspond ing to nine known Arabidopsis mutations, dw3, dw6, ac15, dw7, ga4, ga1, dw1 , axr1 and axr3. The possibility of using Arabidopsis/Brassica as a model t o extrapolate genetic information into other crops was examined.