Molecular characterization of Indian potato (Solanum tuberosum L.) varieties for cold-induced sweetening using SSR markers

Cold-induced sweetening developed during storage of potatoes (Solanum tuberosum L.) at low temperature is a crucial factor influencing the processing quality of potato tubers and remains one of the principal concerns of potato processing industry. Developing CIS-resistant genotypes is the most effective method to cope with this stress. In this study, the genetic diversity of 11 Indian potato varieties with different reactions to CIS was assessed using 10 SSR primers. The primers detected a total of 42 alleles arranged in 44 different configurations, among which 37 alleles (88%) were polymorphic. The polymorphic information content (PIC) value of the SSR locus ranged from 0.473 to 0.787 thus indicating a high utility of these markers for study of genetic diversity in potato. A number of polymorphic fragments appeared to be specific to a given sugar-forming group. Primer Sti007 generated one fragment Sti007131bp present only in all the high sugar-forming varieties. The dendrogram derived from Dice’s similarity coefficients among the 11 varieties could partially but efficiently differentiate close parents and sugar-forming groups among the varieties. These findings demonstrate the effectiveness of SSR markers to assess the genetic variation among potato cultivars in order to develop molecular markers associated with CIS to improve potato breeding programs

Profiling of StvacINV1, BAM1 and INH2α expressions in relation to acid invertase and β-Amylase activities during development of cold-induced sweetening in Indian potato (Solanum tuberosum L.) tubers

Cold-induced sweetening (CIS) characterized by reducing sugars (RS) accumulation during low temperature storage of potato (Solanum tuberosum L.) tubers remains a serious postharvest concern for the potato processing industry. Enzymes involved in carbohydrates metabolism and the genes modulating their activities are of paramount importance in the events associated with the development of CIS. Expression of vacuolar acid invertase gene StvacINV1, β-amylase gene BAM1 and invertase inhibitor gene INH2α and their consequence on acid invertase and β-amylase activities with resulting RS accumulation were followed in one CIS-tolerant (Kufri Jyoti) and one CIS-susceptible (Kufri Badshah) Indian potato varieties stored in cold conditions. Differential gene expression analysis showed that during cold storage, expression of StvacINV1 and BAM1 increased at low temperature and their transcripts were more expressed in the CIS-tolerant variety than the CIS-sensitive. Besides, correlation between BAM1 expression and β-amylase activity affirmed the hypothesis of several enzymes and pathways involved in starch degradation during cold storage of potato. Expression of invertase inhibitor gene INH2α however was higher in the CIS-tolerant variety than the CIS-sensitive. Correlating StvacINV1 and INH2α expressions with RS content and acid invertase activity established that post-translational regulation of acid invertase by the invertase inhibitor protein could be an important component of resistance to CIS