Mapping Of The Control Genes,Conferring The White Petiole In Milk Chinese Cabbage(Brassica Campestris Ssp.Chinensis L.)

Chinese Cabbage(Brassica rapa ssp.Pekinensis)is a very important vegetable crop in East Asia,which has large planting area,great varieties and higher nutritional value.The leaf is the main organ for photosynthesis.The petiole is the nutrients transport channels and supporting the leaf.Petiole color is an important agronomic trait in Chinese Cabbage,which has a wide range of variation,but the basis of variation is not clear.The leaf color of Milk Chinese cabbage is dark green and the petioles are white that is important materials to study the development of petiole color in Chinese Cabbage.In this study,Greens Komatsuna and Milk Chinese cabbage as materials,analyzed the petiole chloroplast ultrastructure,and mapped the petiole color control genes.The main research results are as follows:1.Greens Komatsuna DH line ' G183' and Milk Chinese cabbage DH line ' W171' were as materials used in the present study,researched the changes of total chlorophyll content in petiole.At the seedling stage,the total chlorophyll content of the petioles of Greens Komatsuna and Milk Chinese cabbage was not significantly different.With the continuous growth of plants,the petioles of Greens Komatsuna chlorophyll content increased,while that of Milk Chinese cabbage decreased.At the mature stage,the difference of total chlorophyll content of petiole in Greens Komatsuna and Milk Chinese cabbage can reach 15 times.2.Observation of the chloroplasts in the petiole of Greens Komatsuna and Milk Chinese cabbage by transmission electron microscopy showed that there was a significant difference in the the chloroplast ultrastructure between the two.In the petioles of Milk Chinese cabbage,the starch grains of chloroplasts accumulated more,the arrangement of thylakoids was loose,and the grana lamella were fuzzy and irregular.There is almost no accumulation of starch grains in Greens Komatsuna,the thylakoids are closely arranged,and the grana lamella are neat and clear.3.Genetic analysis indicated that the petiole color difference of Milk Chinese cabbage and Greens Komatsuna is from the nucleus,has nothing to do with the cytoplasm,and the petiole color is quantitative traits.Milk Chinese cabbage and Greens Komatsuna were hybridized to construct F2 segregation population,and chosen the extreme character to built pool strategy(green pool and white pool).Three QTLs control the color of petiole were detected by QTL-seq method,respectively located in A03 chromosomes,44533-1493479 bp,A07 chromosomes 2416474-3445358 bp and A07 chromosome 7612186-9487677 bp.4.Using RNA-Seq technology to analyze the transcriptome of the petioles of Milk Chinese cabbage and Greens Komatsuna,10426 differential expressed genes(DEGs)were detected,including 5405 up-regulated genes and 5021 down-regulated genes.Among these differential expressed genes,24 chlorophyll synthesis genes of Chinese Cabbage were more than twice as different.Through the GO and KEGG enrichment analysis found,that in GO enrichment analysis there are three Term of the significance level higher in the molecular functional is transferase activity,tetrapyrrole binding as well as heme binding,KEGG pathway enrichment analysis found that photosynthesis and the photosynthesis-antenna ptotein pathway enrichment of significance level is higher.