Articles
Potential of Bacillus spp. as biological control agents to suppress anthracnose disease of dragon fruit (Hylocereus undatus)
Article number
1186_20
Pages
135 – 142
Language
English
Abstract
This study in 2012 aimed to screen for bacterial biological control agents that were effective at suppressing anthracnose disease caused by Colletotrichum gloeosporioides (Cg) and Colletotrichum truncatum (Ct) in dragon fruit (Hylocereus undatus). The candidate biological control agents were isolated from surface of twigs of dragon fruit which had been collected from four dragon fruit orchards in Samut Sakhon, Thailand.
Among 265 isolates, four phylloplane bacterial isolates were selected on the basis of their capacity to inhibit the mycelial growth of both Cg and Ct on PDA medium.
Three of the selected isolates (PB182, PB255 and PB257) were identified as Bacillus methylotrophicus and isolate PB223 was identified as Bacillus subtilis. Further tests in PDB medium revealed that isolate PB257 was highly effective in inhibiting not only the mycelial biomass but also conidial germination of Cg and Ct.
Microscopic examination showed that mycelia of these two pathogenic fungi possessed morphological abnormalities, exhibiting bulbous cells when they were co-cultured in the culture medium with these bacteria.
Isolate PB257 produced volatile compounds which were highly effective in inhibiting the mycelial growth of Cg and Ct.
The mycelia of Cg and Ct which had been exposed to the volatile compounds had reduced virulence when they were inoculated onto the wounded surface of dragon fruits.
Isolates PB182 and PB257 reduced the length of necrotic lesions on the twigs of dragon fruit in the laboratory, regardless of when the bacteria were sprayed either 24 h before, followed immediately with fungal inoculation or 24 h after inoculating the pathogens.
Isolates PB182 and PB257 were also effective in reducing disease severity in the greenhouse.
A new product containing these Bacillus spp. isolates should be developed commercially to control anthracnose disease of dragon fruit.
Among 265 isolates, four phylloplane bacterial isolates were selected on the basis of their capacity to inhibit the mycelial growth of both Cg and Ct on PDA medium.
Three of the selected isolates (PB182, PB255 and PB257) were identified as Bacillus methylotrophicus and isolate PB223 was identified as Bacillus subtilis. Further tests in PDB medium revealed that isolate PB257 was highly effective in inhibiting not only the mycelial biomass but also conidial germination of Cg and Ct.
Microscopic examination showed that mycelia of these two pathogenic fungi possessed morphological abnormalities, exhibiting bulbous cells when they were co-cultured in the culture medium with these bacteria.
Isolate PB257 produced volatile compounds which were highly effective in inhibiting the mycelial growth of Cg and Ct.
The mycelia of Cg and Ct which had been exposed to the volatile compounds had reduced virulence when they were inoculated onto the wounded surface of dragon fruits.
Isolates PB182 and PB257 reduced the length of necrotic lesions on the twigs of dragon fruit in the laboratory, regardless of when the bacteria were sprayed either 24 h before, followed immediately with fungal inoculation or 24 h after inoculating the pathogens.
Isolates PB182 and PB257 were also effective in reducing disease severity in the greenhouse.
A new product containing these Bacillus spp. isolates should be developed commercially to control anthracnose disease of dragon fruit.
Authors
P. Meetum, C. Leksomboon, M. Kanjanamaneesathian
Keywords
anthracnose disease, phylloplane bacteria, conidial inhibition, volatile substances
Groups involved
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