Yong-Ho Jeon

Biological Control of Apple Anthracnose by Paenibacillus polymyxa APEC128, an Antagonistic Rhizobacterium

The present study investigated the suppression of the disease development of anthracnose caused by Colletotrichum gloeosporioides and C. acutatum in harvested apples using an antagonistic rhizobacterium Paenibacillus polymyxa APEC128 (APEC128). Out of 30 bacterial isolates from apple rhizosphere screened for antagonistic activity, the most effective strain was APEC128 as inferred from the size of the inhibition zone. This strain showed a greater growth in brain-heart infusion (BHI) broth compared to other growth media. There was a reduction in anthracnose symptoms caused by the two fungal pathogens in harvested apples after their treatment with APEC128 in comparison with non-treated control. This effect is explained by the increased production of protease and amylase by APEC128, which might have inhibited mycelial growth. In apples treated with different APEC128 suspensions, the disease caused by C. gloeosporioides and C. acutatum was greatly suppressed (by 83.6% and 79%, respectively) in treatments with the concentration of 1 × 108 colony forming units (cfu)/ml compared to other lower dosages, suggesting that the suppression of anthracnose development on harvested apples is dose-dependent. These results indicated that APEC128 is one of the promising agents in the biocontrol of apple anthracnose, which might help to increase the shelf-life of apple fruit during the post-harvest period.

Differential Structural Responses of Ginseng Root Tissues to Different Initial Inoculum Levels of Paenibacillus polymyxa GBR-1

Root discs of 4-year-old ginseng, Panax ginseng C. A. Meyer, were inoculated with the higher( colonyforming units(CFU)/ml) and lower( CFU/ml) initial inoculum levels of a plant-growth promoting rhizobacterium(PGPR), Paenibacillus polymyxa GBR-1 to examine rot symptom development and bacterial population changes on the root discs. At the higher inoculum level, brown rot symptoms developed and expanded on the whole root discs in which the bacterial population increased continuously up to 4 days after inoculation. In light and electron microscopy, ginseng root cells on the inoculation sites were extensively decayed, which were characterized by dissolved cell walls and destructed cytoplasmic contents. However, no rot symptoms were developed and the bacterial population increased only during the initial two days of inoculation at the lower inoculum level( CFU/ml) of P. polymyxa GBR-1. At the lower inoculum level( CFU/ml), boundary layers with parallel periclinal cell divisions, structurally similar to wound periderm, were formed internal to the inoculation sites, beneath which the cells were intact containing numerous normal-looking starch granules and no disorganized cell organelles, suggesting that these structural features may be related to the suppression of symptom development, a histological defense mechanism.

Biological characteristics of Bacillus amyloliquefaciens AK-0 and suppression of ginseng root-rot caused by Cylindrocarpon destructans

The effect of Bacillus amyloliquefaciens AK‐0 (AK‐0) on ginseng root rot disease caused by Cylindrocarpon destructans was investigated.

Effects of rhizobacteria Paenibacillus polymyxa APEC136 and Bacillus subtilis APEC170 on biocontrol of postharvest pathogens of apple fruits

In this study, plant growth-promoting rhizobacteria (PGPR) were evaluated as potential biocontrol agents against postharvest pathogens of apple fruits. In vitro bioassays revealed that, out of 30 isolates screened, isolates APEC136 and APEC170 had the most significant inhibitory effects against the mycelial growth of several fungal pathogens. Analysis of 16S ribosomal RNA (rRNA) sequences identified the two effective isolates as Paenibacillus polymyxa and Bacillus subtilis, respectively. The two strains showed greater growth in brain-heart infusion broth than in other growth media. Treatment of harvested apples with suspensions of either strain reduced the symptoms of anthracnose disease caused by two fungal pathogens, Colletotrichum gloeosporioides and Colletotrichum acutatum, and white rot disease caused by Botryosphaeria dothidea. Increased productions of amylase and protease by APEC136, and increased productions of chitinase, amylase, and protease by APEC170 might have been responsible for inhibiting mycelial growth. The isolates caused a greater reduction in the growth of white rot than of anthracnose. These results indicate that the isolates APEC136 and APEC170 are promising agents for the biocontrol of anthracnose and white rot diseases in apples after harvest, and suggest that these isolates may be useful in controlling these diseases under field conditions.中文概要目 的研究APEC136 和APEC170 对苹果采后炭疽病和白腐病的生物防治作用。方 法选择APEC136 和APEC170 两菌株为对象, 通过 16S rRNA 序列分析进行菌种鉴定; 研究不同的 培养基、温度和pH 值等条件对APEC136 和 APEC170 生长影响; 测定其对几丁质酶, 淀粉酶, 纤维素酶和蛋白酶的产量和活性的影响; 分析其 对胶孢炭疽菌(Colletotrichum gloeosporioides)、 尖孢炭疽(Colletotrichum acutatum)和葡萄座腔 菌(Botryosphaeria dothidea)的菌丝生长抑制作 用, 观察苹果采后炭疽病和白腐病症状的变化。结 论16S rRNA 序列分析结果发现两个拮抗菌株分别 为多粘类芽孢杆菌和枯草芽孢杆菌。在脑心浸液 肉汤(BHI)培养基中, 这两个菌株生长最快。 体外生物测定表明, 在筛选的30 株菌株中, APEC136 和APEC170 对胶孢炭疽菌、尖孢炭疽 和葡萄座腔菌的菌丝生长的抑制作用最显著。 APEC136 和APEC170 均减轻了苹果采后由病原 真菌引起的炭疽病和白腐病症状。另外, APEC136 增加了淀粉酶和蛋白酶产量, APEC170 增加了几丁质酶、淀粉酶和蛋白酶产量, 这些可 能是其抑制菌丝生长的原因。综上所述, 菌株 APEC136 和APEC170 是有效的苹果采后炭疽病 和白腐病的生物防治剂, 可用于野外条件下的疾 病控制。

Efficacy of Soil Amendment with Medicinal Plant Materials for the Control of Root-knot Nematode (Meloidogyne incognita) in Tomato

Soil amendments with oriental herbal medicines such as fruit of Anethum graveolens, flower buds of Syzygium aromaticum, rhizome of Cnidium officinale, rhizome of Coptis chinensis, root bark of Paeonia suffructicosa, stem bark of Phellodendron amurense, and stem bark of Cinnamomum cassia at the rate of 0.2% (weight by volume of soil) significantly reduced Meloidogyne incognita infection (root gall formation) of tomato seedlings compared with the control. The most effective treatments were root bark of P. suffructicosa and stem bark of C. cassia as they gave minimum numbers of galls on tomato roots (4.7% and 8.9%, respectively, relative to control) as compared to other treatments. Another study with root bark of P. suffructicosa and C. cassia at different application doses also showed consistent results in reducing gall number. The control efficacy decreased as the application doses were lowered, indicating their dose-dependent control activities. These treatments significantly enhanced aboveground plant growths (total masses).

Involvement of Heat-stable and Proteinaceous Materials in the Culture of Pseudomonas putida JB-1 for the Inhibition of Tobacco mosaic virus Infection

Out of various fungi and bacteria tested for inhibition of Tobacco mosaic virus(TMV) infection using Nicotiana tabacum cv. Xanthi-nc, a bacterial isolate JB-l, identified as Pseudomonas putida had a strong direct inhibitory activity against the TMV infection. Its systemic or indirect activity was also noted at more than a half level of the direct control efficacy. Disease severity was reduced significantly in the susceptible tobacco N. tabacum cv. NC 82 by the treatment of the bacterial culture filtrate, somewhat more by the pretreatment than by simultaneous treatment, probably by inhibiting the TMV transmission and translocation in the plants, showing negative serological, which responses in the viral detection by DAS-ELISA. TMV-inhibitory substances from P. putida JB-1 were water-soluble, stable to high temperature(even boiling), and to a wide range of pH. As proteinase K nullified their antiviral activity, the TMV inhibition activity of P. putida may be derived from proteinaceous materials. In electron microscopy, TMV particles treated with the JB-1 culture were shown to be shrunken with granule-like particles attached on them. All of these aspects suggest that P. putida JB-1 may be developed as a potential agent for the control of TMV.