Kanchalee Jetiyanon

Mixtures of plant growth-promoting rhizobacteria for induction of systemic resistance against multiple plant diseases

Studies of induced systemic resistance using strains of plant growth-promoting rhizobacteria (PGPR) have concentrated on the use of individual PGPR as inducers against multiple diseases of a single crop. To date, few reports have examined the potential of PGPR strain mixtures to induce systemic resistance against diseases of several different plant hosts. The objective of this study was to select mixtures of compatible PGPR strains with the capacity to elicit induced systemic resistance in four hosts. The specific diseases and hosts tested in this study included: bacterial wilt of tomato (Lycopersicon esculentum) caused by Ralstonia solanacearum, anthracnose of long cayenne pepper (Capsicum annuum var. acuminatum) caused by Colletotrichum gloeosporioides, damping off of green kuang futsoi (Brassica chinensis var. parachinensis) caused by Rhizoctonia solani, and cucumber mosaic virus (CMV) on cucumber (Cucumis sativus). To examine compatibility, seven selected PGPR strains were individually tested for in vitro antibiosis against all other PGPR strains and against three of the tested pathogens (R. solanacearum, C. gloeosporioides, and R. solani). No in vitro antibiosis was observed among PGPR strains or against pathogens. Twenty-one combinations of PGPR and seven individual PGPR were tested in the greenhouse for induced resistance activity. Results indicated that four mixtures of PGPR and one individual strain treatment significantly reduced the severity of all four diseases compared to the nonbacterized control: 11 mixtures reduced CMV of cucumber, 16 mixtures reduced bacterial wilt of tomato, 18 mixtures reduced anthracnose of long cayenne pepper, and 7 mixtures reduced damping off of green kuang futsoi. Most mixtures of PGPR provided a greater disease suppression than individual PGPR strains. These results suggest that mixtures of PGPR can elicit induced systemic resistance to fungal, bacterial, and viral diseases in the four hosts tested. 2002 Elsevier Science (USA). All rights reserved.

Broad-spectrum protection against several pathogens by PGPR mixtures under field conditions in Thailand

Prior greenhouse experiments showed that four mixtures of plant growth-promoting rhizobacteria (PGPR) strains (all Bacillus spp.) elicited induced systemic resistance in several plants against different plant pathogens. Based on these findings, we sought to determine if systemic resistance induced by these PGPR would lead to broad-spectrum protection against several pathogens under field conditions in Thailand. Experiments were conducted during the rainy season (July to October 2001) and winter season (November 2001 to February 2002) on the campus of Naresuan University, Phitsanulok, Thailand. The specific diseases and hosts tested were southern blight of tomato (Lycopersicon esculentum) caused by Sclerotium rolfsii, anthracnose of long cayenne pepper (Capsicum annuum var. acuminatum) caused by Colletotrichum gloeosporioides, and mosaic disease of cucumber (Cucumis sativus) caused by Cucumber mosaic virus (CMV). Results showed that some PGPR mixtures suppressed disease more consistently than the individual PGPR strain IN937a. One PGPR mixture, Bacillus amyloliquefaciens strain IN937a + B. pumilus strain IN937b, significantly protected (P = 0.05) plants against all tested diseases in both seasons. Further, cumulative marketable yields were positively correlated with some treatments.

Film coating of seeds with Bacillus cereus RS87 spores for early plant growth enhancement

The plant growth-promoting rhizobacterium Bacillus cereus RS87 was previously reported to promote plant growth in various crops in both greenhouse and field trials. To apply as a plant growth promoting agent with practical use, it is essential to ease the burden of routine preparation of a fresh suspension of strain RS87 in laboratory. The objectives of this study were to investigate the feasibility of film-coating seeds with B. cereus RS87 spores for early plant growth enhancement and to reveal the indoleacetic acid (IAA) production released from strain RS87. The experiment consisted of the following 5 treatments: nontreated seeds, water-soaked seeds, film-coated seeds, seeds soaked with vegetative cells of strain RS87, and film-coated seeds with strain RS87 spores. Three experiments were conducted separately to assess seed emergence, root length, and plant height. Results showed that both vegetative cells and spores of strain RS87 significantly promoted (P < or = 0.05) seed emergence, root length and plant height over the control treatments. The strain RS87 also produced IAA. In conclusion, the film coating of seeds with spores of B. cereus RS87 demonstrated early plant growth enhancement as well as seeds using their vegetative cells. IAA released from strain RS87 would be one of the mechanisms for plant growth enhancement.

Potential of Bacillus cereus strain RS87 for partial replacement of chemical fertilisers in the production of Thai rice cultivars

BACKGROUND There is increasing interest in the development of technologies which can reduce the requirement for chemical fertilisers in rice production. The objective of this study was to investigate the efficacy of Bacillus cereus strain RS87 for the partial replacement of chemical fertiliser in rice production. A greenhouse experiment was designed using different fertiliser regimes, with and without strain RS87. Six Thai rice cultivars were tested separately. RESULTS Maximum rice growth and yield were obtained in rice receiving the full recommended fertiliser rate in combination with the strain RS87. Interestingly, all rice cultivars which were treated with strain RS87 and 50% recommended fertiliser rate provided equivalent plant growth and yield to that receiving the full recommended fertiliser rate only. A paired comparison between rice treated with 50% of the recommended fertiliser rate with the bacterial inoculant and the full fertiliser rate alone was further examined in small experimental rice paddy fields. Growth and yield of all rice cultivars which received the 50% fertiliser rate supplemented with strain RS87 gave a similar yield to that receiving the full fertiliser rate alone. CONCLUSION Bacterial strain RS87 showed the potential to replace 50% of the recommended fertiliser rate for yield production. Integration of plant growth-promoting rhizobacterial inoculants with reduced application rates of chemical fertiliser appears promising for future agriculture.

Physicians´ generic drug prescribing behavior in district hospitals: a case of Phitsanulok, Thailand

Generic prescribing is a sound approach to contain health care costs. However, little is known about physicians’ prescribing patterns in the Thai context. Objective: To explore physicians’ generic prescription patterns in district hospitals. Methods: Data was collected from three of the eight district hospitals between January and December 2008 (final response rate 37.5%). All participating hospitals were between 30 and 60-bed capacity. The researchers reviewed 10% of total outpatient prescriptions in each hospital. Results: A total of 14,500 prescriptions were evaluated. The majority of patients were under universal health coverage (4,367; 30.1%), followed by senior citizens’ health insurance (2,734; 18.9%), and civil servant medical benefit schemes (2,419; 16.7%). Ten thousand six hundred and seventy-one prescriptions (73.6% of total prescriptions) had at least one medication. Among these, each prescription contained 2.85 (SD=1.69) items. The majority of prescriptions (7,886; 73.9%) were prescribed by generic name only. Drugs prescribed by brand names varied in their pharmacological actions. They represented both innovator and branded-generic items. Interestingly, a large number of them were fixed-dose combination drugs. All brand name prescriptions were off patented. In addition, none of the brand-name drugs prescribed were categorized as narrow therapeutic range or any other drug that had been reported to have had problems with generic substitution. Conclusion: The majority of prescriptions in this sample were written by generic names. There is room for improvement in brand name prescribing patterns.

Dose-responses of Bacillus cereus RS87 for growth enhancement in various Thai rice cultivars

To achieve the goal of reducing the levels of chemical fertilizers applied in rice production, there is a need to develop microorganisms with the capacity to enhance plant growth. Previous studies have demonstrated that Bacillus cereus RS87 promotes growth of various plants in greenhouse and field trials. The objectives of this study were to (i) evaluate the efficacy and determine the optimum concentration of B. cereus RS87 to enhance growth of various Thai rice cultivars, (ii) measure the chlorophyll content in leaves affected by strain RS87, and (iii) investigate the capacity of strain RS87 to solubilize phosphate and produce siderophores. Three concentrations of strain RS87 (log 6.0, log 7.0, and log 8.0 CFU/mL) were applied to each rice cultivar. Superior responses (i.e., enhanced development of roots and shoots of all rice cultivars) were observed using RS87 at log 8.0 CFU/mL compared with lower bacterial concentrations and the water-treated control treatment. In addition, log 8.0 CFU/mL of RS87 provided the greatest root length and plant height of all rice cultivars 45 days after planting in the greenhouse. Rice leaves treated with log 8.0 CFU/mL of RS87 yielded the highest total chlorophyll, specifically chlorophyll a and chlorophyll b, compared with the control. Strain RS87 also solubilized phosphate and produced siderophores. The results of these studies demonstrate that log 8.0 CFU/mL is the optimum concentration of strain RS87 for growth promotion of various Thai rice cultivars.