The Premature-bolting Genetic Model And Qtl Reaserch Of Carrot (Daucus Carota L.)

Carrot is one of the world’s top ten vegetables. Carrot cultivation area in China is the first in the world.Recent years, the situation of carrot production and cultivation changes greatly, off-season cultivation and advance listed are the main objectives of production and breeding. However, premature bolting is very serious in the production and cause the yield decreasing sharply.The mechanism and inheritance of carrot premature bolting are studied, and the molecular genetic mapping is constructed by analysising the related QTLs.This will have a significance in carrot resistant-bolting new varieties cultivation.The premature bolting of carrot in spring cultivation was investigated with101accessions including five ecotypes in2004,2005and2008. The results showed that the premature bolting ratio of37accessions of Danvers, Nantes, Amsterdam and Kuroda was zero and that of one Nantes, one Kuroda and three purple accessions were more than20%. The average ratio of purple type was about48.4%, significantly higher than other ecotypes. The average ratio of2004was7.0%, which was higher than that of2005(2.7%) and2008(3.7%). The premature bolting of carrot could be induced with long-day.P1, P2, F1and F2populations derived from a cross between Hubei Songzi70C07and Amsterdam was used to investigate the phenotype date of the premature-bolting. The inheritance of carrot premature bolting was analysised by using joint segregation analysis approach. The results showed that carrot premature-bolting trait was controlled by a pair of additive-dominant major gene plus additive-dominance-epistatic polygenic mixed model, but major gene heritability was very low, only0.24%, polygene rate heritability was93.34%.That might be controlled both by the low temperature and by the light, which induced the bolting phenomenon.F2population was directly seeding in the field in autumn.187plants were random choosed and then used as mapping population. Carrot primary molecular genetic map was constructed with10linkage groups and104SRAP markers by using SRAP marker genetic analyzing. The map covered712.2cM of genomic with an average genetic distance of 6.85cM. Every linkage group had3-43genetic markers, average genetic distance was2.37-9.91cM, and the length of linkage group was7.1-333.8cM.MQM mapping method was used to locate the gene locus and study the genetic effects, which controlled the quantitative trait of carrot bolting. Two effective QTL detected sites B5and B6were found by analysising and comparison. B5’s LOD value was3.41, additive effect was0.532048, contribution rate was5.6%, and that biased towards the female parent wild Songzi (70C07). B6’s LOD value was2.81, additive effect was-1.06545, contribution rate was19.6%, and that biased towards the male parent Amsterdam.