Study on tuberization of Rehmannia glutinosa (Gaertn.) Libosch.

Rehmannia glutinosa (Gaertn.) Libosch. is an herbal plant, which belongs to the Srcophulariaceae family, containing the main active ingredients such as catalpol and verbacoside in its root tubers. In traditional medicine, R. glutinosa tubers have been used in the fresh or dried tuber root or the prepared rehamannia root. They not only possess the comprehensive pharmacological actions in the blood system, endocrine system but also used mainly for anti-tumor treament, immune-enhancement, anti-diabetes, treament for concretion in the urinary tract, etc. R. glutinosa is naturally distributed in China, Korea and Japan. This species was introduced into Viet Nam since 1958 and then planted widely in many the Northern plain and midland provinces. In Vietnam, R. glutinosa produces flowers without seeds, therefore the plant has been mainly propagated by slicing tubers. In this work, we investigated the effect of some plant hormones and sucrose contents on the ability to producing microtubers of R. glutinosa. Experiments were establishmented on the 1/4 MS medium supplemented with 50g/L sucrose. Results showed that auxin (IBA, NAA) had no effect on the in vitro tuber formation of R. glutinosa. The efficiency of using the single BAP or PP333 was low. The highest in vitro tuberization rate of R. glutinosa obtained on the medium supplemented with the combination of BAP (1.0 mg/L) and PP333 (0.3 mg/L), reached 83.33% and the number of tubers/plant was 5.58. The optimal sucrose concentration for increasing the diameter and weight of microtubers was 70 g/L. 100% of plants with tuber-roots survived in the nursery and thrived on the field

Effect of two cytokinins and a growth inhibitor on the in vitro tuberization of two genotypes of Solanum tuberosum L. cvs. Atlantic and Alpha

This investigation was carried out to evaluate the effect of two cytokinins: 6-benzilaminopurine (BAP) (6.5 mg l-1) and kinetin (K) (2.5 mg l-1), as well as the growth inhibitor abscisic acid (ABA) (1.0 mg l-1) on the in vitro tuberization capacity of two potato varieties: Atlantic and Alpha. The basal culture medium MS (1962) was used as a control. The responses were different between varieties. In cv. Atlantic, the analysis of the number (NM), weight (WM) and diameter (DM) of microtubers indicated that the addition of growth regulators did not affect induction and development of microtubers. However, when BAP was used, a non-significant increment of 41 % was observed in the number of the microtubers compared to the control treatment, from 2.6 to 4.4. The addition of cytokinins and ABA to the medium did not have a significant impact on the development of microtubers. In cv. Alpha the cytokinins used without ABA increased the number of microtubers, which were larger and heavier than those of the control treatment. In this variety, ABA significantly reduced the values of the NM, WM and DM variables. The exogenous action of cytokinins in the culture medium is likely to have caused an endogenous hormonal imbalance in the Atlantic and Alpha genotypes which interfered with their innate microtuberization ability, a result that was even more evident for cv. Alpha, which showed the need to continue optimizing protocols of genotype-specific systems in potato tissue culture to increase yield and seed quality.

Identification of Differentially Expressed Genes Using cDNA-AFLP During Six Days In Vitro Tuberization of Potato

Tuberization in potato is a complex developmental process resulting in the differentiation of stolon into the storage organ, tuber. During tuberization, change in gene expression has been known to occur. To study gene expression during tuberization over the time, in vitro tuberization system provides a suitable tool, due to its synchronous in tuber formation. An early six days axillary bud growing on tuber induction medium is a crucial development since a large number of genes change in their expression patterns during this period. In order to identify, isolate and sequencing the genes which displaying differential pattern between tuberizing and non-tuberizing potato explants during six days in vitro tuberization, cDNA-AFLP fingerprint, method for the visualization of gene expression using cDNA as template which is amplified to generate an RNA-fingerprinting, was used in this experiment. Seventeen primer combinations were chosen based on their expression profile from cDNA-AFLP fingerprint. Forty five TDFs (transcript derived fragment), which displayed differential expressions, were obtained. Tuberizing explants had much more TDFs, which developmentally regulated, than those from non tuberizing explants. Seven TDFs were isolated, cloned and then sequenced. One TDF did not find similarity in the current databases. The nucleotide sequence of TDF F showed best similarity to invertase ezymes from the databases. The homology of six TDFs with known sequences is discussed in this paper.