Abstract
Turmeric (Curcuma longa L. (Zingiberaceae)) is a rich source of medicinally important chemical compounds obtained from both pseudostem (aboveground part) and rhizome (underground part). However, the availability of disease-free elite varieties of the plant is highly restricted. Leaf spot caused by Colletotrichum curcumae Butler & Bisby and bacterial wilt caused by Ralstonia pseudosolanacearum Safni have been reported as major diseases responsible for reduced rhizome productivity in the turmeric plant. Meristem culture is a well-known alternative for production of disease-free mother rhizome. The aim of this investigation was to eradicate bacterial and fungal disease instances through culturing of meristematic tissue pretreated with 1.44 to -2.88 mu M GA (gibberellic acid) followed by detection of disease contamination using PCR amplification and chemical assay. Meristem (0.5 to 2.0 mm) was identified as a good material for initiating tissue culture, as it exhibited 100% survival rate and absence of R. pseudosolanacearum and C. curcumae when tested with SPA (sucrose peptone agar), TZC (Kelman's tripheny tetrazolium chloride), and PDA (potato dextrose agar) selective media. Plantlets derived from meristematic tissues of size 2.0 mm were healthy and displayed rapid recovery and uniformity in size. Disease-free status of plantlets (derived from meristem culture) was confirmed by PCR products of specific primers, RP1F/RP1R and RP3F/RP3R for R. pseudosolanacearum and CCactF/CCactR and CChisF/CChisR for C. curcumae. Moreover, shoot elongation using supplemented GA in the culture medium was successfully induced for meristem cutting. All meristem cultures pretreated with GA were confirmed to be contamination-free through TZC, SPA, and PDA media as well as PCR amplification. Based on this study, the 1.0 to 2.0 mm in size of meristem cutting and pretreatment with 1.44 to 2.88 mu M GA for shoot elongation were successfully identified in addition to confirming the disease-free status of the plantlets using chemical assay and PCR products.
