Biocontrol of Fusarium Crown and Root Rot and Promotion of Growth of Tomato by Paenibacillus Strains Isolated from Soil

In this study, bacterial strains were isolated from soils from 30 locations of Samcheok, Gangwon province. Of the isolated strains, seven showed potential plant growth promoting and antagonistic activities. Based on cultural and morphological characterization, and 16S rRNA gene sequencing, these strains were identified as Paenibacillus species. All seven strains produced ammonia, cellulase, hydrocyanic acid, indole-3-acetic acid, protease, phosphatase, and siderophores. They also inhibited the mycelial growth of Fusarium oxysporum f. sp. radicis-lycopersici in vitro. The seven Paenibacillus strains enhanced a range of growth parameters in tomato plants under greenhouse conditions, in comparison with non-inoculated control plants. Notably, treatment of tomato plants with one identified strain, P. polymyxa SC09-21, resulted in 80.0% suppression of fusarium crown and root rot under greenhouse conditions. The plant growth promoting and antifungal activity of P. polymyxa SC09-21 identified in this study highlight its potential suitability as a bioinoculant.

Application of Rhizobacteria for Plant Growth Promotion Effect and Biocontrol of Anthracnose Caused by Colletotrichum acutatum on Pepper

In vitro and greenhouse screening of seven rhizobacterial isolates, AB05, AB10, AB11, AB12, AB14, AB15 and AB17, was conducted to investigate the plant growth promoting activities and inhibition against anthracnose caused by Colletotrichum acutatum in pepper. According to identification based on 16S rDNA sequencing, the majority of the isolates are members of Bacillus and a single isolate belongs to the genus Paenibacillus. All seven bacterial isolates were capable of inhibiting C. acutatum to various degrees. The results primarily showed that antibiotic substances produced by the selected bacteria were effective and resulted in strong antifungal activity against the fungi. However, isolate AB15 was the most effective bacterial strain, with the potential to suppress more than 50% mycelial growth of C. acutatum in vitro. Moreover, antibiotics from Paenibacillus polymyxa (AB15) and volatile compounds from Bacillus subtilis (AB14) exerted efficient antagonistic activity against the pathogens in a dual culture assay. In vivo suppression activity of selected bacteria was also analyzed in a greenhouse with the reference to their prominent in vitro antagonism efficacy. Induced systemic resistance in pepper against C. acutatum was also observed under greenhouse conditions. Where, isolate AB15 was found to be the most effective bacterial strain at suppressing pepper anthracnose under greenhouse conditions. Moreover, four isolates, AB10, AB12, AB15, and AB17, were identified as the most effective growth promoting bacteria under greenhouse conditions, with AB17 inducing the greatest enhancement of pepper growth.

Immunostimulatory Effects of beta-glucan Purified from Paenibacillus polymyxa JB115 on Mouse Splenocytes

We investigated the effects of beta-glucan purified from Paenibacillus polymyxa JB115 on the viability and proliferation of splenocytes. Splenocytes play a critical role in host immunity. MTT assays and trypan blue exclusion tests revealed that beta-glucan significantly promoted the viability and proliferation of splenocytes over a range of concentrations. However, there was no specific subset change. beta-glucan protected splenocytes from cytokine withdrawal-induced spontaneous cell death. For further mechanistic studies, ELISA assay revealed that beta-glucan enhanced the expression of anti-apoptotic molecules and interleukin 7 (IL-7), a cytokine critical for lymphocyte survival. We also investigated the IL-2 dependency of beta-glucan-treated splenocytes to determine if treated cells could still undergo clonal expansion. In flow cytometric analysis, beta-glucan induced increased levels of the activation marker CD25 on the surface of splenocytes and beta-glucan-treated splenocytes showed higher proliferation rates in response to IL-2 treatment. This study demonstrates that beta-glucan can enhance the survival of splenocytes and provides valuable information to broaden the use of beta-glucan in research fields.

Occurrence of Clubroot on Shepherd's-purse Caused by Plasmodiophora brassicae

Clubroot symptoms were frequently observed on roots of shepherd's-purse (Capsella bursa-pastoris) grown in a field in Nonsan, Chungnam province, Korea in March, 2009. Many resting spores were found in the cells of the root gall tissues collected from the field. The clubroot pathogen was identified as Plasmodiophora brassicae based on its morphological and pathological characteristics. This is the first report that P. brassicae causes clubroot of shepherd's-purse in Korea.

Chinese Cabbage Clubroot Pathogen, Plasmodiophora brassicae, Is Genetically Stable

Single spore isolates of Plasmodiophora brassicae e4 and e9 obtained from diseased Chinese cabbage were identified as race 4 and race 9, respectively, by the Williams' differential variety set. To confirm the possibility of variation in same generation and progeny of a single spore isolate of P. brassicae, random amplified polymorphic DNA (RAPD) analysis was conducted using the URP 3, 6 and OPA 7 primers. There was no difference in band type at each part of the gall of Chinese cabbage obtained by inoculation of e4 and e9 and amplification using the URP 3 and 6 primers when the same generation was analyzed. In addition, the progeny analysis, which was expanded to the third generation and conducted using the URP 3 and OPA 7 primers, revealed no differences in the band type of the e4 isolate. Based on these results, the single spore isolate of P. brassicae was genetically stable.

Occurrence of Clubroot on Pak-Choi Caused by Plasmodiophora brassicae

Clubroot symptoms occurred severely on roots of Pak-Choi (Brassica campestris ssp. chinensis) grown in greenhouses in Gwangju city, Gyeonggi province, Korea in September, 2008. The incidence of the disease symptoms reached as high as 90% in three greenhouses investigated. The root galls collected from the greenhouses were sectioned using a scalpel and observed by light microscope. Many resting spores were found in the cells of the root gall tissues. Suspension of resting spores was prepared from the root galls and inoculated to roots of healthy Pak-Choi plants. Each of five resting spore suspensions caused clubroot symptoms on the roots, which were similar to those observed during the greenhouse survey. Resting spores of the pathogen were observed in the cells of the affected roots. The clubroot pathogen was identified as Plasmodiophora brassicae based on its morphological and pathological characteristics. This is the first report that Plasmodiophora brassicae causes clubroot of Pak-Choi.