• The Plant Pathology Journal
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• v.31 no.2
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• pp.152-164
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• 2015

Biological control of major rice diseases has been attempted in several rice-growing countries in Asia during the last few decades and its application using antagonistic bacteria has proved to be somewhat successful for controlling various fungal diseases in field trials. Two novel endophytic Bacillus species, designated strains YC7007 and $YC7010^T$, with antimicrobial, plant growth-promoting, and systemic resistance-inducing activities were isolated from the roots of rice in paddy fields at Jinju, Korea, and their multifunctional activities were analyzed. Strain YC7007 inhibited mycelial growth of major rice fungal pathogens strongly in vitro. Bacterial blight and panicle blight caused by Xanthomonas oryzae pv. oryzae (KACC 10208) and Burkholderia glumae (KACC 44022), respectively, were also suppressed effectively by drenching a bacterial suspension ($10^7cfu/ml$) of strain YC7007 on the rhizosphere of rice. Additionally, strain YC7007 promoted the growth of rice seedlings with higher germination rates and more tillers than the untreated control. The taxonomic position of the strains was also investigated. Phylogenetic analyses based on 16S rRNA gene sequences indicated that both strains belong to the genus Bacillus, with high similarity to the closely related strains, Bacillus siamensis KACC $15859^T$ (99.67%), Bacillus methylotrophicus KACC $13105^T$ (99.65%), Bacillus amyloliquefaciens subsp. plantarum KACC $17177^T$ (99.60%), and Bacillus tequilensis KACC $15944^T$ (99.45%). The DNA-DNA relatedness value between strain $YC7010^T$ and the most closely related strain, B. siamensis KACC $15859^T$ was $50.4{\pm}3.5%$, but it was $91.5{\pm}11.0%$ between two strains YC7007 and $YC7010^T$, indicating the same species. The major fatty acids of two strains were anteiso-$C_{15:0}$ and iso $C_{15:0}$. Both strains contained MK-7 as a major respiratory quinone system. The G+C contents of the genomic DNA of two strains were 50.5 mol% and 51.2 mol%, respectively. Based on these polyphasic studies, the two strains YC7007 and $YC7010^T$ represent novel species of the genus Bacillus, for which the name Bacillus oryzicola sp. nov. is proposed. The type strain is $YC7010^T$ (= KACC $18228^T$). Taken together, our findings suggest that novel endophytic Bacillus strains can be used for the biological control of rice diseases.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.56 no.2
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• pp.124-133
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• 2011

Bacterial blight (BB), cuased by the vascular pathogen Xanthomonas oryzae pv. oryzae, is one of the major threats in rice fields worldwide. In Korea, two resistance genes against BB, Xa1 and Xa3 had been intensively used for developing high quality japonica rice cultivars. Those traditional resistance sources have being rapidly ified by the adopting of BB pathogen through mutations of the corresponding avr-genes, such as K3a exhibiting high compatibility to both Xa1 and Xa3. To expanding genetic resource against BB in Korea, the Suweon506, an introgression line between a Korean japonica cultivar, Hwaseong and a wild relative, Oryza minuta, was be subjected for genetic analysis owing to the BB resistance. Through association analyses between the pathotyping and genotyping results for each $F_2$ progenies, derived from a cross between Suweon506 and a Tongil type cultivar, Milyang23, a major resistant dominant gene is localized on the subterminal region of rice chromosome 4, where at least three BB resistancde genes, Xa1, Xa2, and Xa22, were reported previously.

• Journal of Life Science
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• v.25 no.10
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• pp.1091-1097
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• 2015

We have isolated and characterized an ascorbate peroxidase (APx) gene, OsAPx1 from rice. Northern and Western blot analyses indicated that at young seedling stage, OsAPx1 mRNA was expressed highly in root, shoot apical meristem (SAM) and leaf sheath than leaf. In mature plant, OsAPx1 gene expressed highly in root, stem and flower but weakly in leaf. OsAPx1 gene and protein expression level was induced in leaves inoculated with Magnaporthe oryzae (M. oryzae) and Xanthomonas oryzae pv. oryzae (Xoo). Phytohormones treatment showed that OsAPx1 was up-regulated by jasmonic acid (JA), but was down regulated by ABA and SA co-treatments with JA, resulting that they have antagonistic effect on pathogen responsive OsAPx1 expression. Phylogenetic analysis illustrated that Arabidopsis AtAPx1 has a close relationship with OsAPx1. In AtAPx1 knock out lines, the accumulation of O₂^- and H₂O₂ are all highly detected than wild type, revealing that the high concentration of exogenous H₂O₂ cause the intercellular superoxide anion and hydrogen peroxide accumulation in AtAPx1 knockout plant. These results suggested that OsAPx1 gene may be associated with the pathogen defense cascades as the mediator for balancing redox state by acting ROS scavenger and is associated with response to the pathogen defense via Jasmonic acid signaling pathway.

• Journal of Microbiology and Biotechnology
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• v.19 no.2
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• pp.194-203
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• 2009

$HpaG_{Xooc}$, from rice pathogenic bacterium Xanthomonas oryzae pv. oryzicola, is a member of the harpin group of proteins, eliciting hypersensitive cell death in non-host plants, inducing disease and insect resistance in plants, and enhancing plant growth. To express and secret the $HpaG_{Xooc}$ protein in Bacillus subtilis, we constructed a recombinant expression vector pM43HF with stronger promoter P43 and signal peptide element nprB. The SDS-PAGE and Western blot analysis demonstrated the expression of the protein $HpaG_{Xooc}$ in B. subtilis. The ELISA analysis determined the optimum condition for $HpaG_{Xooc}$ expression in B. subtilis WBHF. The biological function analysis indicated that the protein $HpaG_{Xooc}$ from B. subtilis WBHF elicits hypersensitive response(HR) and enhances the growth of tobacco. The results of RT-PCR analysis revealed that $HpaG_{Xooc}$ induces expression of the pathogenesis-related genes PR-1a and PR-1b in plant defense response.

• Korean journal of applied entomology
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• v.19 no.1 s.42
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• pp.51-55
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• 1980

The study has been carried to confirm pathogenesity among the isolates which obtained from leaf blight type symptoms and Kresek type symptoms, and also to observe varietal resistance among 29 varieties and/or lines through the introduction of two different pathotypes, of Xanthomonas oryzae, by the use of root clipping and pin prick methods. There was no significant differences among the isolates when their growth in plant tissue were compared. There was certain tendency, however, that the isolates from Kreseked plants showed longer lesion than those from blight type lesions. Both isolates from blight type and Kresek type induced the same degree of Kresek syptoms when they were introduced into plants by root cutting in the suspension prior to transplant. Varietal resistance to 'Kresek' appeared to be the same with those on leaf blight type though Wase Aikoku group varieties showed Kresek symptoms which is not the case with leaf blight type. IR 20 in Kogyoku group varieties showed highly resistant reaction to Kresek type. Root clipping method induced the more of Kresek than those by pin pricking method.

• Korean journal of applied entomology
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• v.10 no.2
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• pp.97-101
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• 1971

1. The experiment was conducted to investigate the physiological characteristics on ten isolates of bacterial leaf blight pathogen of rice, Xanthomenas eryzae Dowson. Seven out of tin isolates were isolated from infected leaves of various rice varieties including IR strains in Korea. Isolates S-20 and S-103 were originated from IRRI in Philippines, and isolate H-5809 was allocated by National Institute of Agricultural Science in Japan. 2. All isolates Produced hydrogen sulfide and ammonia 9as from peptone sol. media, and reduced methylen blue, Gelatin liquefaction occurred by all isolates tested, although each isolate showed different degree of liquefaction No coagulation of the casein in milk by the isolates was observed, though some amount of acid production occurred in litmus milk by ail isolates tested. 3. All isolates utilized glucose and galactose, and slight utilization of esculin, mannitol, raffinose, salicin and saccharose was observed. Lactose, starch and dextrin, however, were not utilized at all by all isolates tested in the study.

• The Plant Pathology Journal
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• v.20 no.1
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• pp.52-57
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• 2004

Sclerotinia sp. (isolate BWC98-105) causes stem blight and root rot in Leghum sp., and is presently being evaluated as a potential mycoherbicide for the control of Trifoliorium repens. Bioassays have shown that Sclerotinia sp. produces phytotoxic substance which is biologically active against T. repens. Two biologically active compounds, designated as compoundsI and II, were produced in vitro from the culture filtrate of BWC98-105 isolate Sclerotium sp. Compounds I and II were purified by means of liquid-liquid extraction and $C_{18}$ open column chromatography (300 ${\times}$ 30 mm, i.d). To determine the purity, the purified compounds were analyzed by RP-HPLC. The analytical RP-HPLC column was a TOSOH ODS-120T (150 ${\times}$ 4.6 mm i.d, Japan), of which the flow rate was set at 0.7 mL/min using the linear gradient solvent system initiated with 15 % methanol to 85 % methanol for 50 min with monitoring at 254 nm. Under these RP-HPLC conditions, compounds I and II eluted at 3.49 and 4.13 min, respectively. Compound II was found to be most potent and host specific. However, compound I had a unique antibiotic activity against phytopathogenic bacteria like bacterial leaf blight (Xanthomonas oryzae) on rice, where it played a less important role in producing toxicity on T. repens. No toxin activity was detected in the water fraction after partitioning with several organic solvents. However, toxin activity was detected in the ethyl acetate and butanol fractions. In the leaf bioassay using compound II, the disease first appeared within 4-5 h as water soaked rot, which subsequently developed into well-defined blight affecting the whole plant.

• Korean Journal of Agricultural Science
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• v.4 no.2
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• pp.191-198
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• 1977

This study was conducted to determine the inheritance to bacterial leaf blight in rice. Varieties used in the study were IR1544-349-2, IR1698-237-2, IR1529-680-3, IR28, IR29, RP663-337-7-8-4-1-1, RP291-20, 62-595 and Kele. The isolate of bacteial leaf blight used was 71-23, 76-1 of Xanthomonas oryzae. $F_1s$ were obtained from crosses between resistant and susceptible varieties. Field observation was made from the Parents, $F_1s$ and $F_2$ sagregating population. The result is summaryzed as fallow: 1) The resistance to the bacterial leaf blight (71-23) derived from cultivars IR1529-680-3, IR28, IR29, RP663-337-7-8-4-1-1, RP291-20 and 62-595 was controlled by a single dominant gene. 2) The resistance to the bacterial leaf blight (71-23) derived from cultivars IR1545-339-2, IR1544-340, IR1698-237-2 and Kele was controlled by a single recessive gene. 3) The resistance to the bacterial leaf blight (76-1) derived from cultivars IR1545-339-2, IR1544-340, IR 1698-237-2 was controlled by a single dominant gene. 4) Degree of resistance to the bacterial leaf blight and genetic type were different depending on isolates within the same resistant cultivar. 5) There was no relation between resistance to the bacterial leaf blight and heading days.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.4
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• pp.314-326
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• 2020

This study was carried out to develop a resistant variety against the K3a race of bacterial blight, Xanthomonas oryzae pv. oryzae, through expansion and pyramiding of resistance genes. To develop an elite bacterial blight-resistant cultivar, the breeding process and bacterial blight resistance reactions in advanced backcross lines (ABLs) were analyzed. ABLs21 which contain Xa3 and Xa21, were developed by double backcrossing japonica cultivar Hwanggeumnuri, which has bacterial blight resistant Xa3 gene, and indica variety IRBB21, which havs Xa21 gene, followed by disease resistance bioassay and marker-assisted selection. The resistance genes of ABLs21 were amplified by PCR with the molecular markers 9643.T4 (Xa3) and U1/I1 (Xa21). Hwanggeumnuri and IRBB3 showed resistance reactions against K1, K2, and K3 races, and a susceptible reaction against K3a, K4, and K5 races. IRBB21 showed resistance reactions against K2, K3, K3a, K4 and K5 races, and a susceptible reaction against K1 race. Hwanggeumnuri showed susceptible reactions at the seedling, tillering and adult stages (all stages), whereas ABL21-1 showed moderate resistance at the tillering stage. ABL21-1 showed stable resistance against 18 isolates of K3a race, and the lesion length was shorter than that of the donor parents. In cluster analysis, the HB4032 isolate showed the highest pathogenicity among the 18 isolates. The molecular marker polymorphisms and average substituted chromosome segment lengths of ABLs21 were 63.2 % and 86.1 cM, respectively. Insertion of the donor chromosomal segments occurred in the predicted region of the Xa21 gene of ABLs21.

• Korean journal of applied entomology
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• v.14 no.3 s.24
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• pp.111-131
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• 1975

The study has been carried out to investigate the occurrence, damage, characteristics of the pathogen, environmental conditions affecting the disease outbreak, varietal resistance, forecasting, and chemical control of bacterial leaf blight of rice in Korea since 1964. Bacterial leaf blight of rice became a major disease in Korea since 1960. A correlation was found between the annual increase of epidemics and increase of cultivation area of susceptible varieties, Jinheung, Keumnampung etc. Areal damage within the country showed that the more was at southern province, Jeonnam, Gyeongnam and western coast, and at flooded rice paddy. Yield reduction directly related with the amount of infection on upper leaves at heading stage. Fifty per cent of reduction resulted when the lesion area was more than 60 per cent. Less than 20 per cent of lesion area, however, was not affected so much on yield loss One hundred and six isolates collected from all over the country were classified as 8 strains by using 4 different bacteriophages in 1973. It was, however, only two in 1965. There were some specificities on varietal distributions among the strains such as that the Jinheung attacked mainly by strain A, B, C and I, those attack Kimmaze were A, B, H and I. Most strains were found from Tongil except D and E, whereas Akibare was only variety that attacked by strain E. Low temperature, high humidity, heavy rainfall and insutficient daylight favored the disease epidemics. Especially, typhoon and flooding at heading stage were critical factors. The earlier transplanting the more disease was resulted, and more nitrogen fertilizer application accerelated the diseased development in general. The resistance to the disease varied by growing stage of the sane plants. All of recommended varieties in Korea were susceptible to the disease except Norm No. 6 and Sirogane which moderately resistant. The pathogen, Xanthomonas oryzae, was detectable from extract of healthy seedlings that were grown in the field with an heavy infection previous year. The more bacteriophage in irigation water resulted the more disease outbreak, and the existence of more than 50 bacteriophages in 1ml. of irrigation water were necessary to initiate the disease out break. The curves representing occurrence of bacteriophages and disease outbreak were similar with 15 days interval. The survey of bacteriophage occurrence can be utilized in forecasting of the disease two weeks ahead of disease outbreak. Three applications of chemicals, Phenazin and Sangkel, in weekly intervals at the early satage of out-break depressed the symptom development, and increased yield by 20per cent. Proper period for the chemical application was just before the number of bacteriophage reaches 50 in 1ml. of irrigation water.