Comparative mapping of QTLs determining the plant size of Brassica oleracea

Quantitative trait loci (QTLs) influencing the size of leaves and stems were detected by restriction fragment length polymorphisms (RFLP) in three Brassica oleracea F₂ populations derived from crosses of rapid-cycling Brassica to three B. oleracea varieties, Cantanese, Pusa Katki and Bugh Kana. Morphological traits, including lamina length, lamina width, petiole length, stem length, stem width and node number were evaluated. A total of 47 QTLs were detected based on a LOD threshold of 2.5. Through comparative mapping we inferred that the 47 QTLs might reflect variation in as few as 35 different genetic loci, and 28 ancestral genes. For the trait of lamina length, we identified QTLs corresponding to five ancestral genes, which mapped near the locations corresponding to five known Arabidopsis mutations, rev, axr1, axr3, axr4 and as2. For the trait of stem length, we identified QTLs corresponding to five ancestral genes, which mapped near the locations corresponding to nine known Arabidopsis mutations, dw3, dw6, acl5, dw7, ga4, ga1, dw1, axr1 and axr3. The possibility of using Arabidopsis/Brassica as a model to extrapolate genetic information into other crops was examined. Received: 30 October 2000 / Accepted: 24 November 2000