| Potato is not only a crop which used as food and vegetables but also an importantindustrial material. China is not the center where the potato originated, so the germplasmare all introduced from abroad including wild and native species as well as their derivedclones/cultivars. As germplasm exchange becomes more often and introduction of newgermplasm has been one important part of the breeding programme in China,conservation of germplasm raises an issue of importance for the breeding. In vitro methedhas been applied to conserve potato germplasm since 1980s, but frequent subculture maybring some problems such as material mixing and labor consuming which leading tointerests in slowing-down the growth of the conservations (slow-growth culture). Withthe growth retardant ancymidol (AM), which has been applied to the conservation inrecent years, appropriate concentration of AM, growth and genetic variation of theconserved plantlets were investigated aiming at to prolong the period of keepingconservations in vitro to at least one year without subculture. The results are as below:1. Different concentrations of AM (10μmol/L, 20μmol/L, 25μmol/L, 30μmol/L) wereapplied to potato cultivar "E1" with 2% mannitol as control based on the MS medium.An optimal conservation period of 2% mannitol was 6 months while that for10μmol/L AM was 9 months and other higher AM concentrations 12 months,indicating a retardant effect of AM on potato plantlet growth in vitro.2. Effects of AM concentrations and temperature and their interactions on theconservation were investigated using potato genotypes E3, CE76 and S. chacoense(cha). MS medium supplemented with different concentrations of AM (0, 10, 15, 20and 25μmol/L) were tested under temperatures of 17 and 20℃. Results showed thatthe conservation period was affected significantly by both temperature and AM.Difference in plant height was largely announced between temperatures and amongAM concentrations with more variations were detected in the former than the later,whereas the temperature×concentration interaction was also significant. The survivalrate of the plantiets cultured with AM was over 80% after 12 months culture at 17℃,.3. Thirty-five potato genotypes were employed to evaluate the roles of AM inconservation with concentration of 20μmol/L at 17℃. Although variations existed among genotypes AM had effects of retarding plant growth in general. The dwarfingstrength (in terms of plant height compared to the control that without using AM) wasaccounted for over 50% in 77.1% genotypes, and about half of the genotypes wasfrom 50% to 70%. There were 8 genotypes (CE76, 8#, A92, G12, G11, P11, E3 andG2) showing dwarfing strength lower than 50% but 6 of them (A92, G12, G11, P11,E3 and G2) found significantly different from control.4. After 24 months culture with AM (20μmol/L), single nodes of E3 and cha showed awell sprout development in one week on MS medium (4%sucrose, 0.7%agar) at 20℃with 16h photoperiod, suggesting a long-term culture with AM had little effects onthe successive cultures back to normal conditions.5. Twenty pair of RAPD primers were used to detect genetic variations of E3 and chaplantlets conserved on MS medium added with 20μmol/L AM for 20 monthscomparing to the plantlets cultured on MS medium. There were about 4% of theplantlets showing band difference when PCR was performed with the conservedplants and this variation was increased to 5.1% in E3 using the first subculturedplantlets and 10.4% in cha when the first and second subcultured plantlets weretested.
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