Etiology and Control of Phytophthora Infestans (Mont.) De Bary in Malaysia

Phytophthora infestans (Mont.) De Bary is the causal agent of late blight disease of tomato, a major destructive disease of tomato in Cameron Highlands. The study undertaken was to isolate the pathogen on artificial media. The morphology and cultural characteristics were described. Disease development of P. infestans isolates on tomato was also studied. In-vivo sensitivity of the isolates towards metalaxyl was tested. Disease epidemiology studies were conducted during the two tomato planting periods in Cameron Highlands. Three isolates of P. infestans from Cameron High lands were isolated on Rye Grain Agar (RGrA), V-8 Juice Agar (V8JA) and Rye wholemeal Agar (RWMA) allamended with antibiotics with percentage recovery of 2%, 0.1% and 0.4% respectively. The P. infestans isolates were designated as PIB/01, PIH/01 and PIKR/01. No growth was observed on the two other media viz. Pea Agar and Difco LBA. Successful isolation were aided by baiting using potato tuber slices. Morphological studies of the P. infestans isolate showed that the mean zoosporangia size was 37.25um x 19.71um, mean L/B ratio of 1.91 and mean short pedicel length of 1.60um. Mean zoospores diameter measured 9.99 um. No chlamydospores was produced in culture

Kinetic studies of the partially purified molybdenum-reducing enzyme from Bacillus pumilus strain Lbna

Bacterial based remediation of environmental toxicants is a promising innovative technology for molybdenum pollution. To date, the enzyme responsible for molybdate reduction to Mo-blue from bacteria show that the Michaelis-Menten constants varies by one order of magnitude. It is important that the constants from newer enzyme sources be characterized so that a comparison can be made. The aim of this study is to characterize kinetically the enzyme from a previously isolated Mo-reducing bacterium; Bacillus pumilus strain Lbna. The maximum activity of this enzyme occurred at pH 5.5 and in between 25 and 35 °C. The Km and Vmax of NADH were 6.646 mM and 0.057 unit/mg enzyme, while the Km and Vmax of LPPM were 3.399 mM and 0.106 unit/mg enzyme. The results showed that the enzyme activity for Bacillus pumilus strain Lbna were inhibited by all heavy metals used. Zinc, copper, silver, chromium, cadmium and mercury all caused more than 50% inhibition to the Mo-reducing enzyme activity with copper being the most potent with an almost complete inhibition of enzyme activity observed