M. E. Wagih ¹, G. Alam ², S. Wiryowidagdo ², K. Attia ³

Affiliations
1 Department of Biology, Faculty of Science, University of New Brunswick, Saint John, NB E2L 4L5, CA
2 Department of Pharmacy, Faculty of Natural Sciences, Hasanuddin University, ID
3 Institute of Genetic Engineering, Fudan University, Shanghai, 200433, CN

Abstract

In an attempt to increase the productivity of the pharmaceutical compound canthin-6-one from cell suspension culture of Brucea javanica, a high cell density culture and improved culture conditions have been investigated with focus on culture conditions and stages of growth. The highest yield of canthin-6-one, 26.72 mg g^-l dry cell, was produced intracellular in 50 g L^-1 cell mass. The established cell suspensions were harvested at the age of 40 days and placed into MS medium containing 1.0 mg L-1> 2,4-D, 1.0 mg L-1 NAA, 0.1 mg L-1 Kinetin and 10 mg L-1 tryptophan for 33-40 days, approximately when the cultures were at their late stationary phase of growth. Addition of 20 mg L^-1 tryptophan did not show a significant difference in canthin-6-one production (p>0.05). Higher than 10 mg L^-1 of tryptophan showed adverse effect on the concentration of canthin-6- one alkaloid (p=0.01). Qualitative analysis of chloroform-extracts of dried cells from suspension cultures revealed spots on TLC; and the identity of canthin-6-one was established by comparison of its R_f value (R_f=0.37), its colour reaction with Dragendorff reagent and ammonium sulphate and its behaviour in UV with an authentic sample. Quantification of canthin-6-one alkaloid using TLCdensitometry scanner in response to different concentration of tryptophan as a precursor showed a concentration-dependent response. The production of canthin-6-one at 26.72 mg g^-1 dried cell weight in this study, establishes a methodology of an improved procedure compared to those previously reported and offers an opportunity for production of canthin-6-one alkaloid at an industrial level.

Keywords

Canthin-6-one, Cell Suspension, Brucea Javanica, Secondary Metabolites

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E. Iramu ¹, M. E. Wagih ², D. Singh ³

Affiliations
1 Queensland University, Saint Lucia, Brisbane, AU
2 University of New Brunswick, Department of Biology, Saint John, NB, CA
3 National Agricultural Research Institute, Lae, Papua Niugini, AU

Abstract

Twenty six genotypes selected from the progeny of cycle-3 recurrent selection on the basis of having 10 suckers or more were screened for taro leaf blight (TLB) resistance using in vitro leaf-disc method which detected six genotypes with durable resistance. Field evaluation of the 26 genotypes, compared to the local control cultivar "Numkowec", on the bases of TLB horizontal resistance, high comparable yield (dry matter, corm and cormel weight etc.) and good eating quality identified three superior genotypes, C3-10, C3-12 and C3-22. The three genotypes showed durable resistance to TLB and Coefficient of Infection (CI) = 20, 50 and 80 compared to CI=240 for the local control cultivar "Numkowec". In a different study, the adaptability of the three genotypes were assessed in a range of agro-ecological locations and recommended for release. The breeding program was further advanced to generate cycle-4 population by performing 85 selective partial diallel crosses among the 26 genotypes. Crosses amongst the 26 genotypes were limited to those which flowered naturally or under the effect of gibberillic acid (GA). Various degrees of natural flowering occurred in 58% of the population; however, flowering was enhanced to 82% following the application of 0.5 gl^-1 GA. Crosses among the remaining 23 genotypes were carried out by other workers following the same procedure. A total of 6000 vigorous seedlings generated from bulked progeny seeds of all crosses involving the 49 genotypes, were identified out of more than 10,000 seedlings, and transplanted to the field, constituting cycle-4 progeny population. A preliminary field evaluation of the population's flowering ability, resistance to TLB and agro-morphological characteristics was carried out. A total of 237 genotypes with large size and non-deformed corms with no or little hair were initially chosen for further selection in a range of agro-ecological locations and release of elite lines, which will constitute the parental lines for cycle-5 recurrent selection population.

Keywords

Colocasia esculanta, Recurrent Selection, Taro Leaf Blight

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