Genetic Diversity Of Carrot Germplasm And Method Of Bolting Tolerance Identification

Carrot(Daucus carota L.) is one of the top ten vegetables in the world, and originated in the Afghanistan. Cultivated carrots can be separated into two types: eastern type and western type. However, the origin and domestication of orange-rooted carrot is still not clear. Banga(1963) proposed that orange-rooted carrots might originate in Holland in the early 17 th century and be selected from yellow carrots according to the change of carrot root color in European oil paintings, but it had no genetics evidence. Chinese orange-rooted carrot was presumable domesticated from Koruda type carrots imported from Japan in the end of 19 th century, but there was no evidence. Carrots is cultivated for a long time in China which has wild, yellow, red and orange carrots types, but little know about their origin, domestication and resistances.Genetic diversity were investigated using phenotypic traits and polymorphism SSR markers among 64 Chinese carrot landraces, 56 orange varieties, 3 Syrian w hite landraces, and 4 purple varieties. The result showed that Shannon-Wiener diversity index of varieties was 1.01, lower than landraces(1.15), and the highest was root skin color in landraces’.The number of polymorphic loci of landraces was 141, more than varieties(122). The PIC of primers was 0.50±0.04, and PIC of landraces was also higher than varieties. The result of STUCTURE showed that the gene resource of Chinese carrot landraces was abundant than varieties. According dendrogram cluster analysis based on SSR markers, it showed that the carrot in this study could be divided into two groups: Chinese landraces and orange varieties. Chinese orange landraces were closer with yellow, red landraces than orange varieties, which proposed that it might mutate from red or yellow resources and China has its own domestication process. The premature bolting ratio of 225 varieties or combines, and 272 breeding lines sown in the winter-spring in plastic tunnel were investigated from 2012 to 2014. The result showed that duration of low temperature is major factor on premature bolting. In Beijing region, seed sown in the late of January in plastic tunnel could be as the effective method to identify the carrot premature bolting tolerance.