ASSESSMENT OF GENETIC VARIATION IN POTATO CALLUS TISSUE UNDER SALINITY USING RAPD MARKERS

Agricultural productivity is severely affected by soil salinity. It is estimated that >6% of the world’s land and 30% of the world’s irrigated area already suffer from salinity problems. Expansion of agriculture to semi-arid regions with the use of intensive irrigation will increase the salinity-affected areas. Like most horticultural crops, potato (Solanum tuberosum L.) has low to moderate tolerance to salinity. Attempts to enhance the salt tolerance in potato and other crops through conventional breeding methods have had limited success, warranting the use of alternative biotechnology-based strategies as a rapid means for the production of salt-tolerant genotypes. Plant tissue cultures may be an effective tool to improve salt tolerance through in vitro selection of salt-tolerant cell lines and subsequent regeneration of whole-plants. Previously, a stable potato calli line adapted to grow on 150 mM NaCl was selected and it has been used as a model to study cellular mechanisms of salinity tolerance. The macroscopic appearance of the NaCl-adapted line was similar to that of the control. Although salinity negatively affected the calli growth rate and antioxidant enzyme activities in the salt-adapted cells, an increase in the levels of antioxidant compounds and proline assured survival. In this work, we used the random amplified polymorphic DNA (RAPD) fingerprinting technique to detect the occurrence of genetic polymorphism in response to salt condition and obtain DNA-based markers. After DNA extraction, a total of 40 arbitrary primers were screened, but only eight were found to generate polymorphic band patterns. A total of sixteen well-resolved and reproducible bands were chosen as RAPD markers, which differentiated geno¬typically NaCl-adapted line from the control. RAPD analysis showed that potato cell line grown under salinity is a somaclonal variant that can be used to regenerate plants with improved salt tolerance, which would be very useful in potato breeding programmes.