ABSTRACT
The genetic stability of in vitro propagated potato microtubers was assessed using random amplified polymorphic DNA (RAPD), inter simple sequence repeat (ISSR), simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers. Microtubers were developed through in vitro from potato microplants using standardized protocols. The microtubers were conserved for 1 year under three different culture media and consequently microplants were regenerated for the DNA analyses. During the study, a total of 38 (10 RAPD, 11 ISSR, 12 SSR and 5 AFLP) primers produced a total of 407 (58 RAPD, 56 ISSR, 96 SSR and 197 AFLP) clear, distinct and reproducible amplicons. Cluster analysis revealed 100 % genetic similarity among the mother plant and its derivatives within the clusters by SSR, ISSR and RAPD analyses, whereas AFLP analysis revealed from 85 to 100 % genetic similarity. Dendrogram analysis based on the Jaccard's coefficient classified the genotypes into five clusters (I-V), each cluster consisting of mother plant and its derivatives. Principal component analysis (PCA) also plotted mother plant and its genotypes of each cluster together. Based on our results, it is concluded that AFLP is the best method followed by SSR, ISSR and RAPD to detect genetic stability of in vitro conserved potato microtubers. The in vitro conservation medium (T2) is a safe method for conservation of potato microtubers to produce true-to-type plans.
ABSTRACT
With the objective to develop a practical and effective method of screening potato for drought tolerance, shoot and root growth in microtuber-derived plantlets was studied in vitro in three genotypes with known root mass production under field conditions. Different levels of water-stress were induced using five concentrations of either sorbitol or polyethylene glycol (PEG) in MS medium. Water potential of various media ranged from -0.80 MPa to -2.05 MPa. Water-stress in culture adversely affected plantlet growth, and genotypes differed for their responses. Genotype IWA-1 was less affected than IWA-3 and IWA-5. At the same level of water potential, sorbitol had lower adverse effect than PEG; the latter being sticky. Genotype x sorbitol and genotype x PEG interactions were significant. At 0.2 M sorbitol and 0.003 M PEG, IWA-1 had significantly more roots with higher total root length, root volume, as well as root-dry weight than those of IWA-3 and IWA-5, whereas the latter two genotypes were at par for all these characters. This pattern was similar to the reported pattern of these genotypes for root-dry weight under field conditions. It is concluded that in vitro screening of potato under specific and limited water-stress conditions may provide a system for effectively differentiating the genotypes for their expected root mass production under field conditions.
