• Korean Journal of Organic Agriculture
• /
• v.7 no.1
• /
• pp.137-146
• /
• 1998

Various rhizobacteria was isolated, and was bacterialized into the substrates to clarify the plant growth promoting effects of rhizobacteria on the early growth of red peper seedlings. Total 125 bacterial isolates were primarily isolated and purified from the soils in greenhouse. And four strains were finally screened, based on the antifungal activities against Fusarium sp., Pythium sp. and Rhizoctonia sp. of red pepper plants. The strongest antifungal strain RB 109 has a antagonistic activity against Fusarium sp., Pythium sp. and Rhizoctonia sp. in terms of 66.0%, 65.0% and 66.1%. Early growth of red pepper seedlings was promoted, when cultured solution of rhizobacteria RB 109 was bacterialized into the substrates. Antifungal rhizobacteria RB 109 was identified as Pseudomonas sp. related strains, which has a similarity of 82% to the Pseudomonas sp.

• Research in Plant Disease
• /
• v.15 no.3
• /
• pp.262-265
• /
• 2009

The fungus gnat, Bradysia difformis was examined for its ability to transmit Fusarium oxysporum in PDA culture. Larvae and adults of B. difformis were able to transmit the fungus as ingested and sticking. We constructed GFP-expressed mutants with Fusarium oxysporum, then feed it to larvae of fungus gnat, B. difformis. So that mycelia were placed in the alimentary canal of larva.

• Research in Plant Disease
• /
• v.10 no.4
• /
• pp.248-259
• /
• 2004

A total 115 isolates of Fusarium species from ginseng roots of 'rotted', and soils collected during 1982-1985 in Korea, were identified and classified into 11 species with the Snyder & Hansen System (with reference to Gerlach-Nirenberg's Modified System). The most dominant of these species were F. solani (55 isolates), F. oxysporum (35 isolates), and F. moniliforme (10 isolates) sensu Snyder & Hansen. The other 8 species (15 isolates) were very rarely isolated and previously identified as F. roseum sensu Snyder & Hansen (1945); these were F. equiseti, F. avenaceum, F. graminum, F. arthrosporioides, F. sambucinum, F. reticulatum, F. semitectum and F. poa. Tested for the ability to infect the roots of ginseng (3 yr. old plants) in field condition with the mycelial inoculum, only one isolate of F. solani (34 isolates tested) and one isolate of F. oxysporum (24 isolates tested) were weakly pathogenic to ginseng roots. Any of the isolates (7 isolates tested) of F. moniliforme [Liseola section] were not pathogenic to ginseng. However, all the isolates of tested of the species of Phytophthora cactorum, Pythium ultimum, and Cylindrocarpon destructans were highly pathogenic to ginseng roots. The species of Fusarium solani and Cylindrocarpon destructans were supposed to be a host dominant disease agent in ginseng plant.

• Research in Plant Disease
• /
• v.17 no.2
• /
• pp.148-154
• /
• 2011

This study was conducted to control the seed borne pathogens (Alternaria spp.) of carrot and to examine the seed germination rate by using 13 environment friendly agricultural materials instead of conventional chemicals for organic cultivation. The growth inhibiting effects on pathogens showed the different responses according to each agricultural material and effective 7 materials against seed borne pathogens were selected. Among 7 materials, the carrot seeds sterilized with plant extracts, Tanger Stop and Land Saver were not germinated at all. The germination rate of seeds sterilized with other materials showed the similar levels with reference chemical (Benlate-T) and non-treated seeds. Infection rates of seeds sterilized with seaweed extract, Bellopper for controlling A. radicina and plant extract, Ssial-100 for A. dauci were similar or low infection rate compared with reference chemical. The germination rate and root length of seeds sterilized with Bellopper and Ssial-100 was similar or superior to those of chemical sterilized seeds. The optimal condition seemed to be a little bit different depending on the concentration of materials. As a result, the sterilization of carrot seeds by using the environment friendly materials could be effectively utilized as a technology to inhibit the infection of seed-borne pathogens.

• Korean Journal Plant Pathology
• /
• v.3 no.3
• /
• pp.217-222
• /
• 1987

Pathogenicity of nine Rhizoctonia solani isolates of different anastomosis groups (AG) on seed and hypocotyls of red pepper, cucumber, Chinese cabbage and radish varied considerably from nonvirulent to highly virulent. Rhizoctonia solani AG 1 was highly virulent on the above four plant species. AG 2 type 1 was highly virulent on radish and Chinese cabbage, moderately virulent on red pepper, and AG 2 type 2 was avirulent or weakly virulent except red pepper. R. solani AG 5 was moderately virulent on hosts tested. In general, virulence of the R. solani isolates to a given host varied among anastomosis groups, but not within anastomosis groups. Anastomosis groups lacked host specificity. The pathogenicity was stronger in steam-sterilized soil than in non-sterilized field soil, if the inoculated plants were closely related with orginal host from which the pathogen was isolated. On the other hand, pathogen was more virulent in non-sterilized field soil than in steam-sterilized soil, if the inoculated ones were not closely related. Generally, contrary to other soil-brone plant pathogenic fungi, Rhizoctonia isolates tended to be more virulent in non-sterilized field soil than in the same soil which had been steamed. A potential danger of building up propagules of R. solani in southern horticultural area are discussed in terms of cropping system.

• Research in Plant Disease
• /
• v.13 no.3
• /
• pp.157-163
• /
• 2007

Hot water treatment that is the most appropriate seed disinfection method for organic vegetable farming was evaluated in this study. Among the leafy vegetable seeds lettuce that was the most sensitive to hot water was suitable to treat at $45^{\circ}C$ for 25 min, while Chinese cabbage and radish seeds were optimally treated at $50^{\circ}C$ for 25 min. The treatments resulted in similar or higher seed germination rate than non-treated seeds and promoted plant growth. In addition, fungi such as Alternaria, Aspergillus, Penicillium, or Mucor grown on the seeds were suppressed over 90% and the bacterial growth on lettuce seeds reduced 98.5% by the treatment. Among the fruit vegetable seeds pumpkin that was vulnerable to hot water was suitable to treat at $50^{\circ}C$ for 15 min, while cucumber and hot pepper seeds revealed optimum treatment at $50^{\circ}C$ for 25 min as chinese cabbage and radish. The treatment also showed similar or higher seed germination rate and growth than non-treated seeds. Furthermore, fungi such as Rhizopus, Aspergillus, Penicillium or Mucor grown on the seeds reduced from 72.0% to 95.4%. The bacterial growth on cucumber and red pepper seeds was suppressed from 65.5% to 86.0% by the treatment. Results indicated that the hot water treatment is practical for disinfection of organic vegetable seeds and the optimum temperature and soaking time varied among the seeds.