Inoculation of leaf sections of Withania coagulans with Agrobacterium tumefaciens strain C58C1 (pRiA4) induced transformed roots with the capacity to produce the most important bioactive compounds of Withania species, withanolide A and withaferin A. The hairy roots obtained showed two morphologies: callus‐like roots (CR) with a high capacity to produce withanolides and typical hairy roots (HR) with faster growth capacity and lower withanolide accumulation. The aux1 gene of pRiA4 was detected by PCR analyses in all roots showing callus‐like morphology. However, this gene was only detected in 12.5% of the roots showing typical hairy root morphology. This fact suggests a significant role of aux genes in the morphology of transformed roots. Time course studies of withanolide production showed that withanolide A accumulated during the first part of the culture whereas the maximum accumulation of withaferin A occurred at the end of the culture period. Some transformed root lines, such as HR112 and CR26, showed considerable potential to produce withanolides in a scaled up bioreactor system, especially the important pharmaceutical compound withanolide A.

For successful conservation and breeding of a medicinal species, it is important to evaluate its genetic diversity as well as its content of phytochemical compounds. The aim of the present study was to investigate the genetic variation of Iranian natural populations of W. somnifera and W. coagulans, using the RAPD (random amplified polymorphic DNA) markers, and their withaferin A content. Using 16 RAPD primers, a total of 282 RAPD bands were achieved. The highest and lowest percentages of polymorphism were observed with primers OPAD-15 (100.0%) and OPC-06 (75.0%), respectively. Cluster analysis of the genotypes was performed based on data from polymorphic RAPD bands, using Dice's similarity coefficient and the UPGMA clustering method. Variations in the RAPD results were found to reflect geographical distribution and genetic factors of the plant populations. The HPTLC analysis of the studied samples revealed the presence of withaferin A in W. coagulans and W. somnifera. Moreover, the concentration of withaferin A had a range from 2.2 to 32.5 µg/g DW and was higher in the aerial part than in the root in all used samples. The results of the present study show that there is a high level of variation in the Iranian natural population of Withania, which is significant for conservation and breeding programs to improve production of withaferin A.

No abstract