Seven bacterial isolates (viz., AB05, AB10, AB11, AB12, AB14, AB15, and AB17) were derived from the rhizosphere and evaluated in terms of plant growth-promoting activities and the inhibition of Phytophthora infestans affecting tomatoes in Korea. According to 16S rDNA sequencing, a majority of the is...
Seven bacterial isolates (viz., AB05, AB10, AB11, AB12, AB14, AB15, and AB17) were derived from the rhizosphere and evaluated in terms of plant growth-promoting activities and the inhibition of Phytophthora infestans affecting tomatoes in Korea. According to 16S rDNA sequencing, a majority of the isolates are members of Bacillus, and a single isolate belongs to Paenibacillus. All seven isolates inhibited P. infestans by more than 60% in vitro. However, AB15 was the most effective, inhibiting mycelial growth of the pathogen by more than 80% in vitro and suppressing disease by 74% compared with control plants under greenhouse conditions. In a PGPR assay, all of the bacterial isolates were capable of enhancing different growth parameters (shoot/root length, fresh biomass, dry matter, and chlorophyll content) in comparison with non-inoculated control plants. AB17-treated plants in particular showed the highest enhancement in fresh biomass with 18% and 26% increments in the root and shoot biomass, respectively. However, isolate AB10 showed the highest shoot and root growth with 18% and 26% increments, respectively. Moreover, the total chlorophyll content was 14%~19% higher in treated plants.
Seven bacterial isolates (viz., AB05, AB10, AB11, AB12, AB14, AB15, and AB17) were derived from the rhizosphere and evaluated in terms of plant growth-promoting activities and the inhibition of Phytophthora infestans affecting tomatoes in Korea. According to 16S rDNA sequencing, a majority of the isolates are members of Bacillus, and a single isolate belongs to Paenibacillus. All seven isolates inhibited P. infestans by more than 60% in vitro. However, AB15 was the most effective, inhibiting mycelial growth of the pathogen by more than 80% in vitro and suppressing disease by 74% compared with control plants under greenhouse conditions. In a PGPR assay, all of the bacterial isolates were capable of enhancing different growth parameters (shoot/root length, fresh biomass, dry matter, and chlorophyll content) in comparison with non-inoculated control plants. AB17-treated plants in particular showed the highest enhancement in fresh biomass with 18% and 26% increments in the root and shoot biomass, respectively. However, isolate AB10 showed the highest shoot and root growth with 18% and 26% increments, respectively. Moreover, the total chlorophyll content was 14%~19% higher in treated plants.
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문제 정의
The objectives of this study were to isolate rhizobacteria and to examine their in vitro and in vivo antagonistic activities toward P. infestans affecting tomatoes under greenhouse conditions. The successful in vitro and in vivo suppressions of P.
However, rhizobacteria are usually applied to soil, seeds, or seedlings, wherein they reduce disease through induction of local or systemic resistance in plants [5, 11, 16]. This experiment was also based on soil treatment with antagonistic bacteria for the control of P. infestans affecting tomatoes under greenhouse conditions.
제안 방법
Statistical analysis. Data from the in vitro and greenhouse experiments under production conditions were analyzed using analysis of variance in a completely randomized design. Duncan’s multiple range test was used to compare the means of the treatments in each experiment.
After 2 weeks, individual tomato seedlings were planted in a plastic pot (15 cm in diameter) filled with the same commercial soil with 10% perlite as described above. For each treatment, one replicate and three replications were used in a randomized block design. The bacterial inoculum (108-109 CFU/ml) was applied in the form of soil drenching twice, one week apart.
In order to test the antagonistic activity of selected bacteria toward the pathogen, agar plugs containing fungi from the margins of young colonies and 20 µl of bacteria were placed on the dual medium plates at about 4.5 cm apart and assessed for about 15 days at 28℃ to observe whether any inhibition zone appeared.
Shoots and roots from six plants per treatment were excised, the fresh and dry weights were determined, and disease severity was assessed and the disease incidence rate was also calculated.
Means were obtained from an individual trial, with six replicates per treatment. The experiment was repeated twice, and each replicate consisted of a single pot with one plant per pot.
The plants were grown in a greenhouse maintained at 60% RH, 28 ±2℃ during the day and 25℃ at night, and watered daily.
대상 데이터
Inhibition was expressed relative to a control strain spotted on the same plate. Five replicates were done for the experiment for each pairing. The isolates showing the greatest inhibition were selected as potential antagonistic bacteria.
The P. infestans used in this study was obtained from the Korean Agricultural Culture Collection (KACC), Suwon, Korea (Table 1), and had been isolated from tomato. It was grown on V8 juice agar (200 ml V8 juice, 800 ml distilled water, 3 g CaCO3, and 15 g agar) medium and incubated in 17 ± 2℃ for 7 days.
데이터처리
Duncan’s multiple range test was used to compare the means of the treatments in each experiment.
성능/효과
Among them, six were identified as species of Bacillus and one was identified as Paenibacillus polymyxa, according to 16S rDNA sequencing (Table 1). AB10, AB12, and AB14 were identified as B. subtilis and AB05 was characterized as B. amyloliquefaciens. However, the other two isolates, AB15 and AB11, were identified as P.
infestans was decreased by 64% in comparison with the non-inoculated control. Among the selected biological control agents in this study, isolate AB17 and isolates AB15 and AB12 reduced the shoot and root dry weights by 28% and 26%, respectively. The result presented in Table 3 shows that AB15 suppressed disease by more than 70%, and plants treated with the same isolate also showed less leaf necrosis compared with the others.
Treatment with isolates AB10, AB11, AB15, and AB17 showed a significant increase in at least five growth parameters (Table 4). Among the treatments, isolate AB17 displayed the highest growthpromoting activity in all of the parameters evaluated, except shoot/root length and root dry weight. However, isolate AB10 showed the highest increase in shoot and root length at 18% and 26%, respectively.
Of the seven isolates evaluated in vitro, five isolates (viz., AB05, AB10, AB11, AB12, and AB17) reduced the mycelial growth of P. infestans by more than 70% on dual culture plates (Figs. 1 and 2). However, maximal inhibition was achieved with the isolate AB15 (80.
The main conclusions from the current study are that rhizobacteria isolated from the rhizosphere in Gangwon Province, South Korea, have the ability to control late blight disease in tomato in vitro and under greenhouse conditions. It has also been concluded that these rhizobacteria possess growth-promoting activities when applied to the soil.
The results demonstrated that isolates AB05, AB11, AB15, and AB17 significantly inhibited P. infestans (Table 3). Treated plants looked healthy and showed a lower incidence of late blight.
05) in at least two growth parameters. Treatment with isolates AB10, AB11, AB15, and AB17 showed a significant increase in at least five growth parameters (Table 4). Among the treatments, isolate AB17 displayed the highest growthpromoting activity in all of the parameters evaluated, except shoot/root length and root dry weight.
후속연구
The present study also provides information on the application of rhizobacteria as inoculants in agricultural practice. However, in order to develop the best performing PGPR strains for commercial applications, further selection through molecular study and screening in field trials will be necessary.
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