natural-products-in-plant-pest-management

272 S. Hettiarachi1980), continuous efforts have been made experimenting with various cellsuspension culture techniques with modifications of culture conditions inorder to maximize the production of desired compounds. The research focusingon improvements on both cell culture and bioreactor aspects is the subjectof the review by Zhao and Verpoorte (2007). Nevertheless, further research isnecessary to bring products of C. roseus to the commercial scale. Berberine, anisoquinolene alkaloid, has been produced in cell suspension culture of Tinosporacordifolia at a concentration of 5.5 mg g −1 dry wt in 24 days (Rao et al.,2008). By screening eight cell lines, the authors were able to find one line thataccumulated 13.9 mg g −1 dry weight of berberine. This is a 5–14-fold increasein product formation compared to that of the intact plant. This is an exampledemonstrating the potential of plant cell cultures and somaclonal variationfor the natural product industry. A tenfold increase brings down the cost ofthe product in the market by at least the same magnitude.Cyclotides are small cyclic peptides stabilized by disulfide bonds betweensix conserved cystine residues. Their biological activities include anti-HIV,antimicrobial and insecticidal actions, and hence they are important botanicalsin biocontrol. In addition, due to their high stability, cyclo tides are verygood candidates for the development of drug delivery systems. Dörnenburget al. (2008) developed techniques to produce cyclotides using callus, suspensionculture and hydroponic cultures of Oldenlandia affinis and evaluated themfor Kalata B1 accumulation. In vitro culture produced only up to 15% of KalataB1 in comparison with plants grown in hydroponics. Further improvement isprobable by manipulating culture conditions and the same group reported ahigher rate of cell multiplication in a 25-l photobioreactor (Seydel et al., 2009).They claim that this approach for harvesting Kalata B1 is more profitable thanother methods, such as field cultivation and chemical synthesis.Cell suspension culture is also useful in the synthesis of volatile oils. Bymanipulating culture conditions, Ishikura et al. (1984) obtained a yield of0.005% to 0.01% of volatile oils of the fresh weight of the cells of Cryptomeriajaponica cell suspension.The progress of research in the development of hairy root technology formetabolite production has been reviewed by Guillon et al. in 2006. The delicatenature of the hairy roots is one of the major problems in maintaininghairy root cultures. Srivastava and Srivastava (2007) reviewed the problemsand different technologies available to overcome them. The basic types ofreactors are either liquid phase or gas phase or even a combination of the two.The nature, applications, perspectives and scale up are discussed therein.The hairy root growth, production of the desired substance(s) and secretionmay require different culture conditions. The production can be enhancedby providing the precursors at the right time and the right concentration. Theaddition of cadaverine to hairy root cultures of Nicotiana rustica shifted thealkaloid production in considerable favour of anabasine with a concomitantdiminution of nicotine (Walton et al., 1988), whereas the addition of mentholor geraniol at 25 mg l −1 to hairy root cultures of Anethum graveolens did nothave an impact on the growth and resulted in the transformation of thecompounds to volatile products (Faria et al., 2009). In a recent experiment,