Effects of Melatonin on Colchicine-Treated PLBs of Dendrobium sonia-28 Orchid.

Dendrobium hybrid orchid is popular in orchid commercial industry due to its short life cycle and ability to produce various types of flower colours. This study was conducted to identify the morphological, biochemical and scanning electron microscopy (SEM) analysis in the Dendrobium sonia-28 orchid plants. In this study, 0.05 and 0.075 % of colchicine-treated Dendrobium sonia-28 (4-week-old culture) protocorm-like bodies (PLBs) were treated in different concentrations of melatonin (MEL) posttreatments (0, 0.05, 0.1, 0.5, 1, 5 and 10 µM). Morphological parameters such as number of shoots, growth index and number of PLBs were determined. In the 0.05 and 0.075 % of colchicine-treated PLBs which were posttreated with 0.05 µM MEL resulted in the highest value of the morphological parameters tested based on the number of shoots (84.5 and 96.67), growth index (16.94 and 12.15) and number of PLBs (126.5 and 162.33), respectively. SEM analysis of the 0.05 µM MEL posttreatment on both the colchicine-treated regenerated PLBs showed irregular cell lineages, and some damages occurred on the stomata. This condition might be due to the effect of plasmolyzing occurred in the cell causing irregular cell lineages.

Influence of plant growth regulators (PGRs) and various additives on in vitro plant propagation of Bambusa arundinacea (Retz.) Wild: A recalcitrant bamboo species.

An efficient micropropagation protocol for high frequency plant regeneration was developed using nodal explants derived in vitro seedlings of Bambusa arundinacea which is an important multipurpose and edible bamboo species and recalcitrant to tissue culture. The nodal explants excised from 20-day-old seedlings were cultured on Murashige and Skoog (MS) medium fortified with various concentrations of 6-benzyl amino purine (BAP) and kinetin (KIN) (0.5-5.0 mg/l) alone and/or in combination with 0.5 mg/l of different auxins [indole-3-butyric acid (IBA) α-naphthalene acetic acid (NAA) and indole-3-acetic acid (IAA)] for shoot bud induction. The combination of BAP (3.0 mg/l) and IBA (0.5 mg/l) was found to be the best for the highest percent of shoot bud initiation (87.2%), with 24.2 shoots/explant. The highest frequency (95.2%) of shoot bud multiplication with maximum number of shoots (90.5 shoots/culture) was noticed on medium containing 4% coconut water with 4% sucrose. The regenerated shoot buds were cultured on MS medium supplemented with various concentrations of auxins alone and/or in combination with AgNO3 (0.5-4.0 mg/l) for in vitro rooting. Maximum percent of rooting (85%) was noticed on MS medium augmented with 3.0 mg/l IBA and 2.0 mg/l AgNO3 after 14 days of culture. Well rooted plantlets obtained were established in the field with 92% survival rate. The present plant regeneration protocol could be used for large scale propagation and ex-situ conservation of this important bamboo species in the near future.

Growth profile and SEM analyses of Candida albicans and Escherichia coli with Hymenocallis littoralis (Jacq.) Salisb leaf extract.

Hymenocallis littoralis (Jacq.) Salisb (Melong kecil) commonly known as 'Spider Lily' is an herbaceous plant from the family Amaryllidaceae. Study was carried out to determine the effect of H. littoralis leaf extract on the growth and morphogenesis of two pathogenic microbes, Candida albicans and Escherichia coli. The leaf extract displayed favourable anticandidal and antibacterial activity with a minimum inhibition concentration (MIC) of 6.25 mg/mL. Time kill study showed both microbes were completely killed after treated with leaf extract at 20 h. Both microbes' cell walls were heavily ruptured based on scanning electron microscopy (SEM) analysis. The significant anticandidal and antibacterial activities showed by H. littoralis leaf extract suggested the potential antimicrobial agent against C. albicans and E. coli.

Mosquitocidal activity of a native Bacillus thuringiensis isolate Bt ReX02 from Gunung Jerai Forest, Malaysia against Culex quinquefasciatus and Aedes albopictus.

BACKGROUND AND OBJECTIVE: To evaluate the mosquito larvicidal potential of the native Bacillus thuringiensis isolate BtReXO2, which was isolated from a tropical rain forest ecosystem in Malaysia. This study also aimed at determining the phenotypic and biochemical characteristics of the isolate. MATERIALS AND METHODS: The phenotypic characterization was carried out by growing the isolate in nutrient broth to observe the colonial morphology, vegetative cells, sporulation, motility and haemolytic activity. The parasporal crystal morphology was determined by Coomassie Brilliant Blue (CBB) staining of the sporulated cells and then observed under light microscope. The mosquito larvicidal assay was conducted with the second instar larvae of Culex quinquefasciatus and Aedes albopictus to determine the entomocidal potency of the isolate. The total protein profile was determined by SDS-PAGE. RESULTS AND DISCUSSION: Preliminary phenotypic and biochemical characterization showed that the isolate is motile, an indirect indication of the virulence of the strain and exhibited hemolytic activity, an important feature of antidipteran Bacillus thuringiensis strains. Study on the crystal morphology showed the presence of cuboidal crystals, another characteristic feature of a mosquitocidal Bacillus thuringiensis strains. Bioassay with the second instar larvae of Culex quinquefasciatus, Aedes albopictus established the antidipteran activity of this native Bacillus thuringiensis isolate. Protein profile analysis revealed the unique pattern showing high molecular mass as well as low molecular mass proteins corresponding to the Cry and Cyt proteins respectively. The protein profile is strikingly different from other mosquitocidal strains such as Bacillus thuringiensis subsp.israelensis and Bacillus thuringiensis subsp. jegathesan Periodical introduction of such native strains of Bacillus thuringiensis will add a new weapon in the armoury to manage the vector borne diseases and also in the management of insect resistance.