Ashara Pengnoo

Erratum to: Screening of potential bacterial antagonists for control of sheath blight in rice and development of suitable bacterial formulations for effective application

Soil samples were taken from paddy rice fields in 14 provinces in the southern part of Thailand. Bacteria were isolated from these soils using the soil dilution plate method on King’s B medium and Thornton’s standardised medium. Isolation yielded 323 bacterial isolates which were subsequently tested for their effectiveness in inhibiting mycelial growth of Rhizoctonia solani, the causal agent of sheath blight of rice. Eight isolates were selected for their ability to create a clear zone in a dual culture test. Further tests evaluated the effect of selected bacteria on sclerotial germination and subsequent mycelial growth, and also on the development of sheath blight lesions on excised rice stems. Three bacterial isolates (16,26 and 29) provided the greatest inhibition of sclerotial germination and mycelial growth and maximum suppression of sheath blight lesions. Isolate 26 and subsequently isolate 29 were chosen for formulation studies. Granulated formulations of these bacterial isolates were developed using the wet granulation technique. The main components of these bacterial formulations were bacterial cells, hydrogenated vegetable oil, monohydrate lactose, polyvinyl pyrrolidone, and crosslinked sodium carboxymethyl cellulose. The efficacy of the formulation of isolate 29 in suppressing sheath blight symptoms was similar to that of fresh cells of isolate 29.

Greenhouse and field trials of the bacterial antagonists in pelletformulations to suppress sheath blight of rice caused by Rhizoctoniasolani

Bacterial formulations, produced using both Bacillus megaterium andB. pumilus individually with pharmaceutical technology, were testedunder both greenhouse and field conditions. In the greenhouse testing,some bacterial formulations, for instance For 7 minus Lac and For 16 minusLac, performed as well as freshly prepared bacterial antagonists insuppress sheath blight disease. In the field testing, For 16 minus Lac wasnot effective in suppressing sheath blight development. Failure of the For16 minus Lac to suppress sheath blight disease in the field trial may be dueto the dilution and inactivation of antibiotics produced by B.megaterium in the aquatic environment in the rice field and climaticconditions during the formulation application.

Use of Trichoderma harzianum cultured on ground mesocarp fibre of oil-palm as seed treatment to control Pythium aphanidermatum, a causal agent of damping-off of Chinese kale seedling

Trichoderma harzianum, isolate T 01-22, was cultured on either sorghum grains, ground mesocarp fibre of oil-palm or oil-palm shell, both amended with urea fertilizer (100:1, w/w). T. harzianum cultured on ground mesocarp fibre was then used to coat seeds of Chinese kale (Brassica alboglabra Bailey) to control damping-off of seedlings caused by Pythium aphanidermatum. Biomass of T. harzianum cultured on ground mesocarp fibre of oil-palm was more effective than Captan and Benomyl, but less effective than Metalaxyl, in controlling damping-off of Chinese kale seedlings. Viability of T. harzianum growing on sorghum grains was reduced significantly during 7 months storage, followed by that of T. harzianum cultured on ground mesocarp fibre and oil-palm shell, both amended with urea fertilizer (46-0-0) at 100:1 (w/w).

Scanning electron microscopic examination of a pellet formulation of Bacillus megaterium and B. pumilus, antagonists of Rhizoctonia solani, and survival during storage.

Bacterial formulations, produced using both Bacillus megaterium and B. pumilus individually with pharmaceutical technology, were formulated using a wet granular method. Viability testing in the laboratory revealed that bacterial populations rapidly declined during storage at room temperature (26–30 °C) for 6 months. The scanning electron microscope (SEM) was used to observe bacterial formulations. Both endospores and vegetative cells of B. megaterium and B. pumilus were detected on the formulation surfaces.

Microbial succession in a fermenting of wild forest noni (Morinda coreia Ham) fruit plus molasses and its role in producing a liquid fertilizer

The numbers of lactic acid bacteria (LAB) and yeasts that were present during a wild forest noni ( Morinda coreia Ham) fermentation, the changes in its physico-chemical properties and levels of plant nutrients were investigated. LAB increased rapidly during the first 7 days and were the dominant population until after day 21 when the LAB were declining and the yeasts began to dominate. Identification of the LAB and yeasts to species level showed that the dominant LAB throughout was Lactobacillus plantarum while Lactobacillus pentosus was found but only at day 21. Saccharomyces cerevisiae was the most dominant species of yeast throughout but was slowly replaced by Pichia membranifaciens and then Pichia anomala. Rhodotolura mucilaginosa , an aerobic yeast, was only detected at the beginning of the fermentation process. It is suggested that the Pichia spp. were responsible for consuming lactic acid. After 56 days, the values of pH, acetic acid, ethanol and electrical conductivity in the fermented product were 3.66, 3.34 g L -1 , 16.98 g L -1 and 14.47 mS cm -1 , respectively. Increased amounts of plant nutrients were present at day 56 mostly derived from the degradation of plant material. At day 56 the amounts were as follows (in mg L -1 ): N 633, P 1210, K 4356, Ca 693, Mg 536, Mn 7, B 51, Zn 169, and total carbon/total nitrogen ratio (C/N ratio) 18. Based on the seed germination index (GI) of cherry tomato ( Lycopersicon esculentum Mill), the extract diluted 256-fold gave the best GI of 157%.

Spray-dried powder of Bacillus megaterium for control of rice sheath blight disease: Formulation protocol and efficacy testing in laboratory and greenhouse

A spray-dried powder containing Bacillus megaterium was developed and tested for control of rice sheath blight disease in the greenhouse. The formulation consisted of 20 ml of an endospore suspension of B. megaterium, 20% w/v of skim milk powder and 1.25% w/v of polyvinyl pyrrolidone k-90, that were mixed and spray dried at 120 °C. The powder displayed good physical characteristics, such as a low-moisture content and a high solubility in water. Bacterial viability in the powder was 3.5±0.1 × 1011 cfu/g after production and remained relatively stable (at 2.2±0.1 × 1010 cfu/g) after 12 months of storage at room temperature. In the laboratory, a 0.1% (w/v) aqueous solution of the formulation was effective in inhibiting the mycelia growth of Rhizoctonia solani (98.5±0.1% inhibition). Under greenhouse conditions, a 0.1% (w/v) aqueous solution applied by either spraying 1 day before inoculating R. solani or spraying 1, 7 and 15 days after inoculation of rice plants with R. solani was more effective in suppressing sheath blight disease than the blank formulation but was less effective than a chemical fungicide control.