Isolation of antagonistic Streptomyces sp. against a potato scab pathogen from a field cultivated with wild oat

Abstract

Fungi, actinomycetes, and bacteria isolated from soil and plant samples from a potato field in which wild oat (Avena strigosa) had been pre-cultivated were screened for microorganisms that can be used as biocontrol agents for common scab of potato. Of 342 isolates assessed in initial pot trials for their suppressive effect on the severity of potato scab caused by Streptomyces turgidiscabies, 26 isolates were selected as antagonistic candidates based on their ability to reduce disease severity, then tested in a second pot trial. Of the 26, five actinomycetes, isolated from either the rhizosphere soil of wild oat or the soil adhering to potato stolons and tubers, were selected as antagonists. A comparison of partial sequences of 16S rRNA genes from the five isolates indicated that they belong to the genus Streptomyces. Of these five, WoRs-501 most strongly inhibited in vitro mycelial growth of S. turgidiscabies and was also the most effective in suppressing potato scab in a third field pot trial. In that pot trial, a 10% (v/v) mix of WoRs-501 (6.2 9 10 8 colony-forming units [CFU]/g dry mass) decreased the disease severity by 78-94% in comparison with the untreated control at 5 9 10 4 to 5 9 10 6 CFU S. turgidiscabies/g dry soil. WoRs-501 also grew well in vitro at a wide range of pH levels and temperatures. These results suggest that WoRs-501 is a promising candidate for biocontrol of potato scab.

Community Analysis of Root- and Tuber-Associated Bacteria in Field-Grown Potato Plants Harboring Different Resistance Levels against Common Scab

“…Actinomycetes are known for their potential suitability as biocontrol agents for potato common scab ( 2 , 13 , 18 , 22 , 50 ). Three dominant OTUs (AC5, AC16, and AC24) with high identities to A. nicotinovorans , S. rishiriensis , and R. baikonurensis were identified in the roots of most of genotypes examined ( Table S2 ).…”

“…is known to exhibit antagonistic activity against several pathogens of the potato ( 40 ). Several bacteria from the genus Bacillus ( 11 , 28 , 38 ) are also known for their potential suitability as biocontrol agents, and a species in this genus has been commercialized in Japan as a control agent for common scab ( 18 ). The high stability of Paenibacillus and Bacillus in the potato rhizosphere suggests that they are suitable candidates for controlling common scab from an ecological viewpoint.…”

“…The characteristics of the soil samples are shown in Table 2 . Tubers in the corresponding field described above were also sampled on August 30, 2010 and disease severity in the tubers was evaluated as described previously ( 18 ).…”

“…Biological control is considered as a desirable approach for controlling soil-borne diseases because it is eco-friendly and expected to replace or supplement chemical pesticides ( 51 ). A number of antagonistic microorganisms including fungal species from the genus Trichoderma ( 19 , 30 ); actinomycetes from the genus Streptomyces ( 2 , 13 , 18 , 22 , 50 ); general soil bacteria from the genera Bacillus ( 11 , 28 , 38 ); Pseudomonas , Enterobacter , and Acinetobacter ( 46 ); and bacteriophages ( 27 ) are known for their potential suitability as biocontrol agents for potato common scab. However, only limited success has been achieved in the development of a commercial application to control common scab using these microorganisms because of the inconsistent performance of biocontrol agents in field conditions, and, hence, this has become an important technical issue in the development and utilization of beneficial microorganisms in agronomic environments.…”

Investigation of Streptomyces scabies Causing Potato Scab by Various Detection Techniques, Its Pathogenicity and Determination of Host-Disease Resistance in Potato Germplasm

“…Potato scab disease is transmissible from seed and soil sources [ 31 , 32 ]. The disease develops when the tuber starts emerging in the first growth stages of tubers when enlarges or direct penetration to the epidermis and enlarging the potato tuber [ 33 ].…”