Genetic analysis and fine mapping of the LOBED-LEAF 1 (BnLL1) gene in rapeseed (Brassica napus L.)

The lobed-leaf character is a clearly recognizable morphologic trait in rapeseed (Brassica napus L.) that has potential advantages in hybrid production. The present study was carried out to analyze the effect of lobed-leaf trait on agronomic traits and to fine map the LOBED-LEAF 1 (BnLL1) gene in B. napus. The lobed-leaf line Yuye 87 and entire-leaf cultivar Zheyou 50 were used to produce four F2 and eight BC1 populations for genetic analysis. Multiple comparison analysis between lobed-leaf character and agronomic traits was carried out in two F2 populations of reciprocal crosses between Yuye 87 and Zheyou 50. Results show that the lobed-leaf phenotype is controlled by a single an incomplete dominant gene and has no significant adverse effects on 10 main agronomic traits. The location of BnLL1 gene was narrowed down to a 36.7-kb homologous region of B. rapa between genes Bra009506 and Bra009511. On the basis of the annotation of orthologous genes in Arabidopsis, Bra009510 is considered to be a promising candidate for BnLL1 gene. The AT5G03790 is the orthologous gene of Bra009510 in Arabidopsis thaliana, with known functions in the formation of simple serrated leaves and in the suppression of bract formation. It is suggested that previously described lobed-leaf gene BnMOSAICLEAF (BnML) and the BnLL1 are the same genes controlling the lobed-leaf phenotype in B. napus, whereas the lobed-leaf gene BcLEAFLOBED 1 (BcLL1) is their homologue in Brassica campestris ssp. chinensis. These findings will facilitate the cloning and functional identification of the BnLL1 gene in future studies.