Fusarium verticillioides (teleomorph Gibberella moniliformis) is associated with maize worldwide causing ear rot and stalk rot, and produces fumonisins, a group of mycotoxins detrimental to humans and animals. While research tools are available, our understanding of the molecular mechanisms associated with fungal virulence and fumonisin biosynthesis in F. verticillioides is still limited. One of the restraints that hampers F. verticillioides gene characterization is the fact that homologous recombination (HR) frequency is very low (<2%). Screening for a true gene knock-out mutant is a laborious process due to a high number of ectopic integrations. In this study, we generated a F. verticillioides mutant (SF41) deleted for FvKU70, a gene directly responsible for non-homologous end-joining mechanism, with the aim of improving HR frequency. Here, we demonstrate that FvKU70 deletion does not impact key Fverticillioides phenotypes, e.g., development, secondary metabolism, and virulence, while dramatically improving HR frequency. Significantly, we also confirmed that a high percentage (>85%) of the HR mutant strains harbor a desired mutation with no additional copy of the mutant allele inserted in the genome. We conclude that SF41 is suitable for use as a type strain when performing high-throughput gene function studies in F. verticillioides.

Aurofusarin is a polyketide pigment produced by some Fusarium species. The PKS12 and GIP1 genes, which encode a putative type I polyketide synthase (PKS) and a fungal laccase, respectively, are known to be required for aurofusarin biosynthesis in Gibberella zeae (anamorph: Fusarium graminearum). The ten additional genes, which are located within a 30 kb region of PKS12 and GIP1 and regulated by a putative transcription factor (GIP2), organize the aurofusarin biosynthetic cluster. To determine if they are essential for aurofusarin production in G. zeae, we have employed targeted gene deletion, complementation, and chemical analyses. GIP7, which encodes O-methyltransferase, is confirmed to be required for the conversion of norrubrofusarin to rubrofusarin, an intermediate of aurofusarin. GIP1-, GIP3-, and GIP8-deleted strains accumulated rubrofusarin, indicating those gene products are essential enzymes for the conversion of rubrofusarin to aurofusarin. Based on the phenotypic changes in the gene deletion strains examined, we propose a possible pathway for aurofusarin biosynthesis in G. zeae. Our results would provide important information for better understanding of naphthoquinone biosynthesis in other fdarnentous fungi as well as the aurofusarin biosynthesis in G. zeae.

A total of 33 isolates of Colletotrichum species obtained from pepper, apple, and strawberry in 2001 and 2002 were identified based on mycological characteristics, responses to fungicides carbendazim and the mixture of carbendazim and diethofencarb, and nucleotide sequence analysis of internal transcribed spacer (ITS) regionMost of the Colletotrichum isolates from pepper could be identified as C. acutatum. The pepper isolates produced grey white mycelia that gradually changed to dark gray. The conidia were variable in size, and almost cylindrical in shape with at least one rounded end. They could grow on PDA amended with carbendazim or with the mixture of carbendazim and diethofencarb at $10{\mu}g/ml$, to which the isolates from apple and strawberry were very sensitive. A part of the ITS regions from the Colletotrichum isolates was amplified with the specific primers designed for C. acutatum (Ca1-1) or C. gloeosporioides (Cg1-3). A primer pair of Ca1-1 and a universal primer (ITS4) amplified a 496-bp DNA fragment from all of the pepper isolates examined and one apple isolate. Taken together, it is conclusive that the Colletotrichum isolates causing the typical lesion of anthracnose on pepper fruits are C. acutatum.

Colletotrichum gloeosporioides forms an appressorium, a specialized infection structure, to infect its hosts. Among 400 and 600 culture filtrates from fungi and class Actinomycetes, six methanol extracts (A5005, A5314, A5387, A5560, A5597, and A5598) from the class Actinomycetes significantly inhibited appressorium formation in C. gloeosporioides infecting pepper fruits in a dose-dependent manner, while conidial germination was slightly enhanced. Two (A5005 and A5560) of them also exhibited distinctive inhibitory effect on the disease progress of pepper anthracnose. Water fractions of both culture filtrates also specifically inhibited appressorium formation in C. gloeosporioides and pepper anthracnose disease. Inhibition of appressorium formation by culture filtrate of A5005 was partially restored by the exogenous calcium. This results suggests that chemicals within A5005 extents its biological activity through disturbance of intracellular $Ca^{2+}$ regulation during prepenetration morphogenesis by C. gloeosporioides. Together, cell-based and target-oriented screening system used in this study should be applicable for other plant pathogenic fungi prerequisite appressorium formation to infect their hosts.

The presence of Chrysanthemum stunt viroid (CSVd) in seed and pollen of diseased chrysanthemum was demonstrated. In seeds infected male parent from crosses in May, CSVd was transmitted to 6.7% of the progeny seedlings, whereas if the female parent was infected, CSVd transmission rate was between 46.9 and 75.7%. A relatively high incidence of 94.4 to 96.0% seed transmission occurred when both parents were infected. In seeds infected male parent from crosses in December, no progeny seedlings were infected with CSVd, whereas if the female parent did, CSVd transmission rate was 1.5%. When both parents were infected, 6.9% seed transmission was occurred. The seed transmission rate depended on the temperature when the crosses were made. CSVd was not detected in the non-infected female parent pollinated with infected pollen but was transmitted to the progenies. This is the first report of seed-borne transmission of CSVd in chrysanthemum.

Studies with the transmission electron microscope were used to detect and attempt to identify viruses infecting sweetpotato (Ipomoea batatas) and other Ipomoea species. Flexuous-rods, short curved-rods, and spherical virus-like particles were observed in cells of symptomatic plants. Also, various cytopathic changes such as crystals, vesicles, fibril structures, and cylindrical inclusions were observed. The present study showed that some of these cytopathic changes were associated with some viral groups, which might be helpful in diagnosis.

With the goal of achieving better integrated pest management for hot pepper, a disease-forecasting system was compared to a conventional disease-control method. Experimental field plots were established at Asan, Chungnam, in 2005 to 2006, and hourly temperature and leaf wetness were measured and used as model inputs. One treatment group received applications of a protective fungicide, dithianon, every 7 days, whereas another received a curative fungicide, dimethomorph, when the model-determined infection risk (IR) exceeded a value of 3. In the unsprayed plot, fruits showed 18.9% (2005) and 14.0% (2006) anthracnose infection. Fruits sprayed with dithianon at 7-day intervals had 4.7% (2005) and 15.4% (2006) infection. The receiving model-advised sprays of dimethomorph had 9.4% (2005) and 10.9% (2006) anthracnose infection. Differences in the anthracnose levels between the conventional and model-advised treatments were not statistically significant. The efficacy of 10 (2005) and 8 (2006) applications of calendar-based sprays was same as that of three (2005 and 2006) sprays based on the disease-forecast system. In addition, we found much higher the IRs with the leaf wetness sensor from the field plots comparing without leaf wetness sensor from the weather station at Asan within 10km away. Since the wetness-periods were critical to forecast anthracnose in the model, the measurement of wetness-period in commercial fields must be refined to improve the anthracnose-forecast model.

Twenty isolates of Bacillus spp. obtained from livestock manure composts and cotton-waste composts were tested for in vitro antagonistic effects against soilborne plant pathogenic fungi, Fusarium oxysporum, Phytophthora capsici, Rhizoctonia solani AG-4, and Sclerotinia sclerotiorum. Seven isolates of Bacillus spp. had antagonistic effects on mycelial growth of all the isolates of F. oxysporum tested. The bacterial isolate RM43 was the most effective to inhibit the mycelial growth of the fungal isolates. Twelve isolates of Bacillus spp. had antagonistic effects on mycelial growth of all the isolates of P. capsici tested. The bacterial isolates M34 and M47 were very effective to inhibit the mycelial growth of the fungal isolates. Thirteen isolates of Bacillus spp. had antagonistic effects on mycelial growth of all the isolates of R. solani AG-4 tested. The bacterial isolates M27 and M75 were very effective to inhibit the mycelial growth of the fungal isolates. Fourteen isolates of Bacillus sp. had antagonistic effects on mycelial growth of all the isolates of S. sclerotiorum tested. The bacterial isolates M49 and M75 were very effective to inhibit the mycelial growth of the fungal isolates. The antagonistic effects of most Bacillus spp. isolates against the isolates of the four fungi differed depending on the fungal species and the isolates of each fungus. The bacterial isolates M27 and M75 were the most effective to inhibit the mycelial growth of all four fungi.

Utilization of carbon sources by Bacillus cereus D324, a biological control agent, and Pythium species, which causes rice seedling disease, was studied with the objective of increasing the efficacy of biological control by providing the biological control agent with specific beneficial carbon sources. D-galactose, D-sorbitol, and D-mannitol were poor carbon sources for Pythium spp. growth but were good for B. cereus D324 growth. Growth in a growth chamber of rice seeds coated with B. cereus D324 amended with specific carbon sources, such as D-galactose and D-sorbitol, showed significantly enhanced seedling emergence compared to seeds coated only with B. cereus D324. Field trials showed that both seedling emergence and yield increased, when the above specific carbon sources were added to B. cereus D324 in seed coating formulations. This result indicated that amending seed coating formulations with specific carbon sources could significantly increase seedling emergence and yield in the field.

The fermentation broth (FB) of Streptomyces griseofuscus 200401 isolated from non-farming soil showed antagonistic activity against powdery mildew fungus both in melon leaf/seedling assay and in field trials. The FB of S. griseofuscus 200401 was tested at different concentrations. In primary test, the control value of 2-fold diluted FB of S. griseofuscus 200401, compared to control, reached to 82.8%. The protective activity recorded 80.5% in 2-fold dilution of FB. The effect was reduced to 28.9% in high dilution (100-fold) treatment. The curative effect was relatively lower than protective activity. In field test, the antifungal activities of S. griseofuscus 200401 remained low in blocks sprayed with 100-fold diluted FB and the control values were 15.2 and 15.9% in 2005 and 2006, respectively. However, the activities were as high as 65% and 67.3% in the blocks treated with 2-fold dilution of FB during the same period.

Seedling damping-off and bottom rot caused by Rhizoctonia solani are yield limiting diseases of crisphead lettuce. To provide biocontrol measure in the management of the diseases, biocontrol strain Pseudomonas aeruginosa LY-11 was isolated from lettuce rhizosphere and introduced into crisphead lettuce rhizosphere by the seed coating delivery method. Alginate was used as a coating material to generate beads containing $10^6-10^{6.5}$ colony-forming units (CFUs) of viable bacterial cells of LY-11. When seeds germinated from the alginate beads containing the strain LY-11, the bacteria established mostly in plant rhizosphere to maintain at least $10^4$ CFU per gram of plant tissues. Crisphead lettuce seedlings germinated from the entrapped seeds were less affected from damping-off and bottom rot with disease control values of 70.4% and 85.4% respectively. Although P. aeruginosa LY-11 colonized plant rhizosphere and not phyllosphere, the result indicated that bottom rot caused by the foliar inoculation of R. solani was effectively reduced by the rhizobacteria. All data suggested that immobilized rhizobacterial application in seeds by alginate coating could control damping-off and induce induced systemic resistance of crisphead lettuce to reduce bottom rot.

This research was conducted to evaluate fungal and bacterial populations in unhulled and brown rice under indoor storage conditions, and to examine the relationship between microbial populations and environmental conditions such as temperature and relative humidity. The temperature and relative humidity of the storage room ranged from $22.6^{\circ}C\;to\;27.0^{\circ}C$ and 23.3% to 44.2%, respectively. Total fungal and bacterial populations remained relatively stable over the storage period. Predominant fungi included Aspergillus candidus, A. flavus, A. fumigatus, and Penicillium spp.; the predominant bacteria were Bacillus, Microbacterium, Sphingomonas, and Methylobacterium spp. Total fungi and bacteria were not significantly correlated with either unhulled (r=0.448, P=0.372) or brown (r=0.466, P=0.351) rice. In unhulled rice, total fungi showed positive correlations with total Aspergillus (r=0.994, P<0.001) and total Penicillium (r=0.906, P<0.05); A. flavus was positively correlated with total Aspergillus (r=0.913, P<0.05) and total fungi (r=0.868, P<0.05). In brown rice, Bacillus spp. was also positively correlated with total bacteria (r=0.998, P<0.001). Mean temperature was negatively correlated with A. candidus (r=-0.852, P<0.05) and total fungi (r=-0.961, P<0.01), and mean relative humidity was positively correlated with total Penicillium spp.(r=0.884, P<0.05) in brown rice. Hence these results could provide basic information on the fungal and bacterial populations in unhulled and brown rice stored under room conditions, and on the effect of environmental conditions on the populations of fungi and bacteria, especially Aspergillus and Penicillium spp.

Anthracnose symptoms were frequently observed on fruits of peach trees grown in Yeongi in Korea during disease survey in August from 2000 to 2005. The disease incidence was as high as 40% at its maximum in the orchards investigated. A total of 24 isolates of Colletotrichum species were obtained from the anthracnose symptoms, out of which 20 were identified as Colletotrichum gloeosporioides and the four remaining ones as C. acutatum based on their morphological and cultural characteristics. Two isolates of each C. gloeosporioides and C. acutatum caused anthracnose symptoms on the fruits by both wound and unwound inoculation, which were similar to those observed in the orchard. The symptoms appeared more rapidly by the wound inoculation than by the unwound inoculation. There was no difference in pathogenicity between the C. gloeosporioides and C. acutatum isolates tested. In Korea, only C. gloeosporioides has been recorded as the causal fungus of anthracnose of peach tree. This is the first report that C. acutatum also causes anthracnose of peach tree in Korea.

Field surveys and specimen collections of the rust fungal pathogen Gymnosporangium were carried out for 15 years from 1985 through 1999 in various locations of Korea. Macroscopic and microscopic examinations of morphological characteristics of aecia from the collected specimens revealed that Gymnosporangium globosum is the causal agent of American hawthorn rust disease on Crataegus pinnatifida and C. pinnatifida varmajor. The host plants are new for this rust fungus. G. globosum was found only in Gyeonggi and Chungbuk provinces, indicating that its distribution in Korea is limited. This is a first full description on morphological characters of aecia of G. globosum in Korea.

A blue mold on tomato fruit caused by Penicillium oxalicum occurred sporadically in a greenhouse at Gyeongsangnam-do Agricultural Research and Extension Services. Infection usually occurred through wounds or cracks on the fruits. Symptoms began with water soaking lesions, then became watery and softened eventually. Colony of the causal fungus was white at the early growing stage, turned green on Czapek yeast extract agar and malt extract agar. Conidia were ellipsoidal in shape and $2-6{\times}2-4{\mu}m$ in size. Stipes were septate, smooth, thin walled, and $90-280{\times}3-4{\mu}m$ in size. Penicilli were mostly biverticillate. Ramuli were 1-3 groups, smooth, and $10-16{\times}2-3{\mu}m$ in size. Rami were 1-2 groups and $6-30{\times}2-4{\mu}m$ in size. Metulae were 2-3(5) verticils, smooth, and $12-20{\times}3-4{\mu}m$ in size. Phialides were 5-7 verticilate, ampulliform to cylindroidal, smooth, and $8-12{\times}2-3{\mu}m$ in size. Optimum temperature for growth was about $25^{\circ}C$. Pathogenicity of the fungus was proved on tomato fruit according to Koch's postulation. On the basis of mycological and pathological characteristics, the fungus was identified as P. oxalicum Currie & Thom. This is the first report of the blue mold on tomato fruit caused by P. oxalicum in Korea.

In 2007, a bulb rot of Allium victorialis var. platyphyllum Makino caused by Sclerotium rolfsii occurred sporadically in a herb farm at Gyeongsangnam-do, Korea. The symptom initiated with water-soaking lesion and progressed into bulb rot and wilt of a whole plant. Severely infected plants were blighted and killed eventually. White mycelial mats appeared on the lesion at early stage and a number of sclerotia were formed on the bulb. The sclerotia were spherical, $1{\sim}3 mm$ and white to brown. The optimum temperature for the growth and sclerotia formation was $30^{\circ}C$ on PDA. The hyphal width was measured $4-9{\mu}m$. The typical clamp connections were observed on PDA. Based on the symptom, mycological characteristics and pathogenicity to the host plant, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report on the bulb rot of A. victorialis var. platyphyllum caused by S. rolfsii in Korea.

In August 2006, a severe disease incidence showing mosaic and/or necrotic symptoms on two bell pepper varieties including red-colored 'Special' and yellow-colored 'Fiesta' was observed in a greenhouse located in Gwangyang, Jeonnam province, Korea. To identify causal viruses, total RNAs were extracted from 11 fruit samples with and without symptoms. Specific oligonucleotide primers for Cucumber mosaic virus (CMV), Pepper mottle virus (PepMoV), Tomato spotted wilt virus (TSWV) and Pepper mild mottle virus (PMMoV) were designed based on the sequences available on GenBank. Database comparisons of the deduced amino acid sequences of each sequence produced 100% and 98% matches with nucleocapsid protein gene of TSWV (Acc. No. ABE11605) and coat protein gene of CMV (Acc. No. DQ018289), respectively, suggesting that the symptoms on bell pepper fruits might be caused by the infection of CMV and TSWV. To our knowledge this is the first report of necrotic as well as mosaic virus disease on bell pepper fruits by the infection of CMV and TSWV in Jeonnam province, Korea.

Leaf blight symptoms and abnormal defoliation were found on Stachys riederi var. japonica, a medicinal plant, grown at Hongcheon, Gangwon province, Korea in 2007. A foliar nematode, Aphelenchoides fragariae was isolated from infected leaf tissues. The symptoms observed on host plant were leaf blotching, discoloration and browning of tissues, tan-colored interveinal necrotic lesions and large dead patches of necrotic tissues. This is the first report of A. fragariae occurring on S. riederi var. japonica.