EST Analysis Of Tipburn In Chinese Cabbage

As one of most important economic crops and extensively cultivated vegetables, Chinese cabbage (Brassica campestris L. ssp. Pekinensis) was originated from China. It is also a main vegetable for export. However, the tipburn happened in Chinese cabbage is limiting their exportation. Breeding for tipburn resistant variety is a difficult subject due to the lack of resistant germplasm as well as the understanding of the resistance mechanism. Tipburn is a physiological disorder induced by calcium deficiency. There is significantly difference in resistance to tipburn existed in China cabbage germplasm. Therefore, breeding for resistant to tipburn has become a hotspot in Chinese cabbage breeding. In this study, detached leaves of Chinese cabbage were used to identify the resistance and character of symptom differences among ten Chinese cabbage materials through insert method under low calcium. In order to analyse molecular mechanism, the suppressive subtraction hybridization (SSH) technique was sued in this work, and expression sequence tags (ESTs) were analyzed in the process of tipburn.The results show that: 2mmol/L EDTA-Na2 is proper concentration to screening the tipburn resistance of Chinese cabbage by using detached leaves; 10 varieties have expressed obviously differences in tipburn resistance; the location and symptom of tipburn appeared in leaves are related with different varieties, and the symptom mainly distributed on the marginal and petiole of leaves; it is considered that this method is suitable to screening the tipburn resistance because of its simple, convenient, economical and practical.Using a tipburn sensitive variety B120, a suppression subtractive cDNA library has been constructed with the cDNAs of calcium deficiency as tester and untreated leaves as driver. Total of 525 ESTs were identified encoding putative proteins. Among of them, 428 coded for known functional proteins, 74 for the hypothetical, putative and unknown proteins. The best matched protein sequences with those encoded by the 428 ESTs were from 13 plant species. According to the function, 428 ESTs are classified to 12 resembles: metabolism; disease/defence; energy; singal transduction; transport; cell degradation; transcription; protein synthesis; cell structure; cell growth/division; secondary metabolism; miscellancous. It indicated that there were many complicated factors included the process of tipburn development. Expression patterns of some genes might play an improtant role in this process. All the above results should provide basis for further study on tipburn of Chinese cabbage.