| Drought is always one of the main abiotic stresses that constrained crop production. In recent years, frequency of drought has been increasing, which put severe risk on food security. In China, most of potato production is located in areas where is either less water resources or uneven rainfall. Therefore, to breed varieties with strong tolerance to drought should be a vital option. For the breeding, to evaluate drought tolerance, to understand mechanism and genetics and to identify genetic background of potato germplasm are crucial issues for potato breeding in china.Thirty cultivars with different maturing time were used as materials. Yields and physiological and biochemical index were identified both under drought and irrigated conditions fluctuations of those indicators of all materials tested were observed. By means of main element analysis, relationship between drought tolerance and biological indicators with different varieties was analyzed. Furthermore, integrated evaluation on drought tolerance was made by tolerant index and fuzzy function. A pair of primer was designed according to the conserved regions of the Fe-SOD mRNA from the tomato in Genbank. The gene was amplified by PCR from the total DNA which was extracted from eight different drought resistance varieties. Then gene fragment was amplified and cloned from Kexin 19. The main results are as follows:1,Yield, physiological and biochemical indicators of potato were deeply affected by drought stress. Responses were different among materials tested, but the tendencies of responses were the same. Under drought stress yields of all varieties decreased obviously comparing to control. In terms of biological and physiological indicators, the leaf relative water content, the water retention capacity of excised-leaf, and oxidation ofα-naphthyamine in root were decreased and malondialdehyde content, the super oxidase dimutase and the proline content were increased under drought stress. The correlation is notable between six physiological indicators and drought tolerant index. So they are more important in potato breeding.2,The results of main element analysis showed that drought tolerances affected by physiological indicators in different maturity potato varieties were not constant. Water retention capacity of excised leaf, super oxidase dimutase and malondialdehyde content are important in early-maturing varieties. Activities of super oxidase dismutase andα-naphthyamine oxidation, and leaf relative water content are important in mid-late-maturing varieties. Activities ofα-naphthyamine oxidation, malondialdehyde content, and leaf relative water content are important traits in late- maturing varieties. 3,By means of drought tolerant index and fuzzy function analysis, drought tolerances of varieties tested were evaluated. The result showed that Chenggong, Kexin-2, Kexin-9, FL1533 and FL1771 can be recognized as category of high drought tolerance. However, Kexin-18, Kexin-13 and NY-128 were in the category of low drought tolerance.4,By homologous based cloning, a gene fragment relevant to drought tolerance was separated from DNA extracted from leaves of Kexin19. Then we blast the sequence with Fe-SOD of other plants on NCBI website. We find they have high homologous, named StFe-SOD. This gene had been registered in GenBank. The access number is EU545469. The length of the sequence is 1413bp, contains four extrons and three introns, and encodes 145 amino acids. The molecular weight is 16,255 kDa, its isoelectric is 5.88. This sequence has two domains about encoding Fe-SOD protein.
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