Assessment And Mechanism Study For Freezing Tolerance In Solanum Acaule Seedling

The common cultivated potato (Solanum tuberosum L.) usually does not tolerate to frost, which often leads to serious yield reduction in potato production. Meanwhile, the wild specie of Solanum acaule is with very resistant to frost under -7℃to -8℃. It could be one of the important gene resources for freezing tolerance in cultivated potato genetic improvement. In the present study, 25 progeny clones from S. acaule and the variety of Zhongshu 3 were used to evaluate the freezing tolerance, the changes of physiological and biochemical index related to the freezing tolerance during cold acclimation. The main conclusions are as follows:1. The cluster analysis for the results of artificial freezing treatments to 26 experimental genotypes showed that the variety of Zhongshu 3 was sensitive to the freezing without any cold acclimation ability. Among 25 progenies of Solanum acaule,12 were sensitive to the frost,11 were tolerant and 2 were very tolerant to freezing; after 7 days cold acclimation, the progenies with sensitive to the frost declined to 3 while the tolerant and very tolerant increased to 12 and 10, respectively. The LT50 for the experimental genotypes before cold acclimation, and after, the cold acclimation ability were high significantly related to the field freezing rating score, and the correlation coefficient were 0.50, 0.91 and-0.55, respectively. It is concluded that the artificial freezing results could be used to forecast the frost tolerance in field in potato production.2. The results for physiological parameters related to the freezing tolerance during cold acclimation indicated that: the chlorophyll contents of 03079-435 from S.acaule and the variety of Zhongshu 3 decreased; the changes of MDA were similar between the 2 genotypes; the proline content of 03079-435 increased first and then decreased but more than that before cold acclimation, while the proline content of Zhongshu 3 was decreasing; the content of soluble sμgar of two genotypes increased, however the content of soluble sμgar of 03079-435 was more than that of Zhongshu 3 during cold acclimation; The soluble protein content of 03079-435 was increasing with the cold acclimation while Zhongshu 3 kept it stable and lower level than that of 03079-435. The results sμggested that the increases of contents of proline and soluble protein be closely associated to the high cold acclimation ability of potato.3. No significant correlation between potato freezing tolerance and the band numbers of POD isoenzyme was found by the proxdase isoenzyme electrophoresis. The freezing tolerance and cold acclimation capacity were closely related to the colour and width of POD isoenzyme band. The bands from the genotypes with freezing tolerance showed deeper color and wider than those from the sensitive plants. The high cold acclimation capacity of genotypes was bound up with the deep colour of POD isoenzyme band after cold acclimation.