QTL Analysis Of The Main Agronomic Traits About Carrot Root

Cultivated carrot?Daucus carota L.var.sativus Hoffm,2n=2x=18?is an economical and nutritional biennial vegetable.The fleshy root is the main commercial organ,and the phenotypic traits are affected by genotype and environmental cues.Molecular assistant selection?MAS?is considered as the effective way for crop breeding and the high density genetic map must be constructed.Based on the carrot genome sequence,a high density genetic map was constructed by re-sequencing with backcross inbred lines?BILs?and 15 agronomic traits of fleshy root were analyzed in this study.1.Phenotypic genetic variation of 223 backcross inbred lines?BILs,BC₂S₆?developed from a crossing between wild species‘Songzi'?Ws?and European orange cultivar‘Amsterdam'?Af?were investigated to understand the function of Ws chromosome fragments.The results showed that leaf length,root length,root weight,root shoulder width,plant weight,root middle width/root length were standard normal distribution,and that the top four principal components could explain 80.36%and83.28%of the accumulated variation,respectively.Correlation analysis showed that root weight and plant weight were significantly related with the other traits,and that dry matter content was positively related with leaf weight/root weight,but negatively with root weight,root shoulder width,root middle width,root tip width,plant weight,and root middle width/root length.2.One hundred and ten lines were randomly selected from the above BIL population and re-sequenced.5.6 Gbp,5.6 Gbp,and 77.51 Gbp clean base of Af,Ws,and 110 lines were obtained,respectively.3,223,700 SNPs were detected by GATK.Genotype coverage of Af and Ws was significantly different among BILs,76.37%⁹9.36%and 0.64%²3.63%,respectively.The genotype and cluster analysis indicated that Ws chromosome fragments were randomly introgressed into Af.A high density genetic map with 2027 Bins and 154,776 markers was constructed,and total map length and average map distance were 1436.433 cM and 0.709 c M,respectively.3.Based on the above genetic map,42 QTLs were detected about 15 agronomic traits by CIM method based on the 95%confidence interval.RL2-1,RSW2-2,RSW/RMW2-1,and RSW/RMW2-2were shared between 2014 and 2015,which could explain 33.73%,39.12%,66.92%,and 66.92%of phenotypic variance,respectively.21 predicted genes were detected with function annotations.LOC108219060 gene was glucose-1-phosphate adenylyltransferase small subunit in starch synthesis and associated with DMC4-1.LOC108209579 gene was exocyst complex component EXO70A1-like with polar auxin transport and associated with RSW/RMW2-2 and RMW/RTW2-2.LOC108195860gene was myosin-17-like that can promote the growth of lateral root and associated with RMW/RTW7-1.