Effect of long-term in vitro subculturing on quality degeneration of sweetpotato varieties: morpho-anatomic assessment and simple sequence repeat (SSR) analysis.

Abstract

True-to-type clonal fidelity is one of the most important prerequisites in micropropagation of crop species. The aim of this study was to assess the effect of long-term in vitro subculturing on the variety degeneration of three sweetpotato varieties (Monate, Mokone and Ndou). Monate was subcultured for 32 generations, whereas Mokone and Ndou were subcultured for 23 and 12 generations, respectively. The media used for subculturing contained 4.43 g/l of MS (Murashige and Skoog) salt, 30 g/l of sucrose and 2 g/l of gelrite. The plantlets were grown in a 16 h light and 8 h dark photoperiod for 30 days, and single node cuttings taken from the 30-day-old plantlets were used as the explant source to subculture the next generation. From each generation, 45 plantlets were transplanted and grown for 2 months in a glasshouse. Data on in vitro growth performance, as well as morphology during acclimatization were recorded. The plantlets which showed a change in morphological traits were subjected to genetic analysis by using five simple sequence repeat (SSR) primers (IB-242, IB-318, IB-255F, IB-248 and IB-255). Significantly higher growth performance, such as stem height, leaf number, internode length, as well as early root and shoot organogenesis, was observed after the 27th and 21st subcultured generations of Monate and Mokone, respectively. Furthermore, plantlets of the same variety showed differences in morphological traits such as leaf colour, abaxial leaf pigmentation, vine pigmentation, petiole pigmentation, leaf wrinkling and percentage of flowering. However, there was no correlation between the subcultured generation and the degree of morphological variability. From the five SSR loci, only IB-255F and IB-318 were able to distinguish between the three varieties. However, no allelic polymorphisms were detected between short-term and long-term propagated plantlets with the primers used in this experiment. Therefore, long-term nodal subculturing did not lead to quality degeneration of sweetpotato varieties Monate, Mokone and Ndou.

Selection of Sweetpotato Parental Genotypes Using Simple Sequence Repeat Markers

“…[ 23 ] on 25 ARC sweetpotato genotypes and 6 local landraces using five SSR markers, while Ref. [ 24 ] used SSR markers for fingerprinting of individual plants of three ARC cultivars. Laurie and coworkers [ 25 ] fingerprinted nine orange-fleshed and three cream-fleshed ARC sweetpotato cultivars and elite clones using seven tested SSR markers.…”