• The Plant Pathology Journal
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• v.31 no.3
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• pp.245-251
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• 2015

Alternative hosts increase the difficulty of disease management in crops because these alternate hosts provide additional sources of primary inoculum or refuges for diversity in the pathogen gene pool. Agropyron cristatum (crested wheatgrass), Bromus inermis (smooth bromegrass), Pascopyrum smithii (western wheatgrass), Stipa viridula (green needlegrass), and Thinopyrum intermedium (intermediate wheatgrass), commonly identified in range, prairie, verge, and soil reclamation habitats, serve as additional hosts for Pyrenophora tritici-repentis, the cause of tan spot in wheat (Triticum aestivum L.). A. cristatum (five lines), B. inermis (seven lines), P. smithii (four lines), S. viridula (two lines), and T. intermedium (six lines) were tested for their reactions to 30 representative P. tritici-repentis isolates from races 1-5. Plants were grown until the two-three-leaf stage in a greenhouse, inoculated individually with the 30 isolates, held at high humidity for 24 h, and rated after 7 days. All lines developed lesion types 1-2 (resistant) based on a 1-5 rating scale. Also, leaves from an additional plant set were infiltrated with two host selective toxins, Ptr ToxA as a pure preparation and Ptr ToxB as a dilute crude culture filtrate. All lines were insensitive to the toxins. Results indicate that these grass hosts have a limited or nonsignificant role in tan spot epidemiology on wheat in the northern Great Plains. Additionally, the resistant reactions demonstrated by the grass species in this research indicate the presence of resistance genes that can be valuable to wheat breeding programs for improving wheat resistance to P. tritici-repentis.

• The Plant Pathology Journal
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• v.33 no.1
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• pp.43-52
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• 2017

A survey was conducted to determine the status of Lucerne transient streak virus (LTSV) in three high-yielding alfalfa regions in central Saudi Arabia (Riyadh, Qassim, and Hail) during 2014. Three hundred and eight symptomatic alfalfa, and seven Sonchus oleraceus samples were collected. DAS-ELISA indicated that 59 of these samples were positive to LTSV. Two isolates of LTSV from each region were selected for molecular studies. RT-PCR confirmed the presence of LTSV in the selected samples using a specific primer pair. Percentage identity and homology tree comparisons revealed that all Saudi isolates were more closely related to each other but also closely related to the Canadian isolate-JQ782213 (97.1-97.6%) and the New Zealand isolate-U31286 (95.8-97.1%). Comparing Saudi isolates of LTSV with ten other sobemoviruses based on the coat protein gene sequences confirmed the distant relationship between them. Eleven out of fourteen plant species used in host range study were positive to LTSV. This is the first time to document that Trifolium alexandrinum, Nicotiana occidentalis, Chenopodium glaucum, and Lathyrus sativus are new host plant species for LTSV and that N. occidentalis being a good propagative host for it.

• Korean Journal of Medicinal Crop Science
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• v.22 no.4
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• pp.306-312
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• 2014

Endophytes are microorganisms that live in the internal tissues of plants without harming the host plants. In this symbiotic relationship, the host plants provide nutrients and shelter to the endophytes, in turn, endophytes can promote the growth of host plants and act as a biological control agents against plant pathogens. Plant-microbe interactions like this are noted for natural methods for sustainable agriculture and environmental conservation. However, in spite of the infinite potential, there are only a few reports on the endophytes present in ginseng. In this study, we isolated and identified the endophytes from Panax ginseng seeds and evaluated the biological activities (IAA production ability, nitrogen fixation ability, phosphate solubilization capacity, siderophore production ability, and antifungal activities) of the endophyte isolates. Eight different endophytes were identified by 16S rRNA sequencing. Most of the endophytes have antibiotic and plant growth promoting (PGP) activities. Particularly, PgSEB5-37E have the highest antibiotic activity, both PgSEB5-37B and PgSEB5-37H have high PGP traits such as an abilities to produce IAA, solubilize phosphate and fix nitrogen. These results indicated that the endophytes from P. ginseng seeds may have applicable value to many industries. In order to use the isolated endophytes, quantitative analysis and field tests are needed to be performed.

• Journal of Microbiology and Biotechnology
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• v.25 no.8
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• pp.1349-1360
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• 2015

The rhizospheric zone abutting plant roots usually clutches a wealth of microbes. In the recent past, enormous genetic resources have been excavated with potential applications in host plant interaction and ancillary aspects. Two Pseudomonas strains were isolated and identified through 16S rRNA and rpoD sequence analyses as P. fluorescens QAU67 and P. putida QAU90. Initial biochemical characterization and their root-colonizing traits indicated their potential role in plant growth promotion. Such aerobic systems, involved in gluconic acid production and phosphate solubilization, essentially require the pyrroloquinoline quinine (PQQ)-dependent glucose dehydrogenase (GDH) in the genome. The PCR screening and amplification of GDH and PQQ and subsequent induction of mutagenesis characterized their possible role as antioxidants as well as in growth promotion, as probed in vitro in lettuce and in vivo in rice, bean, and tomato plants. The results showed significant differences (p ≤ 0.05) in parameters of plant height, fresh weight, and dry weight, etc., deciphering a clear and in fact complementary role of GDH and PQQ in plant growth promotion. Our study not only provides direct evidence of the in vivo role of GDH and PQQ in host plants but also reveals their functional inadequacy in the event of mutation at either of these loci.

• Research in Plant Disease
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• v.29 no.3
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• pp.286-294
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• 2023

Biological and molecular characterization of a Korean isolate of Orthotospovirus chrysanthinecrocaulis (formerly known as chrysanthemum stem necrosis virus, CSNV) isolated from Chrysanthemum morifolium was determined using host range and sequence analysis in this study. Twenty-three species of indicator plants inoculated mechanically CSNV-Kr was investigated for determination of host range. CSNV-Kr induced various local and systemic symptoms in the inoculated plant species. CSNV-Kr could not infect three plant species and induced symptomless in systemic leaves in Nicotiana tabacum cultivars, though the plant samples reacted positively with the antiserum to CSNV by double-antibody sandwich-enzyme-linked immunosorbent assay. The complete genome sequence of CSNV-Kr was determined. The L RNA of CSNV-Kr consists of 8,959 nucleotides (nt) and encodes a putative RNA-dependent RNA polymerase. The M RNA of CSNV-Kr consists of 4,835 nt and encodes the movement protein (NSm) and the glycoprotein precursor (Gn/Gc protein). The S RNA of CNSV-Kr consists of 2,836 nt and encodes NSs protein and N protein. The Gn/Gc and N sequence of CSNV-Kr were compared with those of previously published CSNV isolates originating from different countries at nucleotide and amino acid levels. The Gn/GC sequence of CSNV-Kr shared 98.8-99.5% identity with CSNV isolated from other countries and the N sequence of CSNV-Kr shared 98.8-99.6% identity. No particular region of variability could be found in either grouping of viruses. All of the CSNV isolates did not show any relationship according to geographical origins and isolation hosts, suggesting no distinct segregation of the CSNV isolates.

• Korean Journal Plant Pathology
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• v.10 no.3
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• pp.240-244
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• 1994

Watermelon plants grafted with the root-stock of wild-cucumber (Sicyos angulatus) were not infected by Fusarium oxysporum f.sp. niveum in pot inoculation and infected fields tests. Controlling efficacy of the root-stock grafting with S. angulatus on Fusarium wilt of watermelon was more excellent than that of the root-stock grafting with Lagenaria siceraria. The isolates of Fusarium oxysprum from cucurbitaceae plants had a certain host-specific pathogenicity, but they did not express the absolute one forma specialis-one host-plant phenomenon by the root dipping inoculation. The pathogenic isolates of Fusarium oxysproum from cucurbitaceae crops did not infect the root-stock plant such as S. angulatus, L. siceraria and Cucurbita ficifolia. The fast-wilting of watermelon caused by uncertain agents was observed in watermelon plant grafted with L. siceraria in the continuously cropping fields, but it was not observed in watermelon plants grafted with S. angulatus in the same fields.

• Korean Journal Plant Pathology
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• v.14 no.6
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• pp.622-624
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• 1998

During the course of study on plant parasitic nematodes associated with medicinal herbs in Korea, high population of different stages of citrus nematode, Tylenchulus semipentrans was found in association with Pyrola japonia Klenze in Imsil, Chunbuk province. The second stage larvae and males were isolated from rhizosphere soil ; immature and mature females were detached from the roots of infested plants of Pyrola japonica. Besides citrus it has been reported to parasitize on roots of Syringa vulgaris, Diospyros lotus, olive, grapevine, and pear in different parts of the world. This is the first record of T. semipenetrans parasitized on a medicinal plant, Pyrola japonica.

• The Plant Pathology Journal
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• v.40 no.3
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• pp.299-309
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• 2024

The rice blast disease, caused by the fungal pathogen, Magnaporthe oryzae (syn. Pyricularia oryzae), poses a significant threat to the global rice production. Understanding how this disease impacts the plant's microbial communities is crucial for gaining insights into host-pathogen interactions. In this study, we investigated the changes in communities of bacterial and fungal endophytes inhabiting different compartments in healthy and diseased plants. We found that both alpha and beta diversities of endophytic communities do not change significantly by the pathogen infection. Rather, the type of plant compartment appeared to be the main driver of endophytic community structures. Although the overall structure seemed to be consistent between healthy and diseased plants, our analysis of differentially abundant taxa revealed the specific bacterial and fungal operational taxonomic units that exhibited enrichment in the root and leaf compartments of infected plants. These findings suggest that endophyte communities are robust to the changes at the early stage of pathogen infection, and that some of endophytes enriched in infected plants might have roles in the defense against the pathogen.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.4
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• pp.316-324
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• 2004

Sinorhizobium sp. strain MUS10 forms nitrogen-fixing stem nodules on Sesbania rostrata, a tropical green manure crop. In this study, the ultrastructural events associated with the formation of stem nodules were investigated. Sinorhizobium sp. strain MUS10 entered the host tissue through cracks created by the emerging adventitious root primordia and multiplied within the intercellular spaces. During early phases of infection, host cells adjacent to invading bacteria revealed cellular damage that is typical of hypersensitive reactions, while the cells at the inner cortex exhibited meristematic activity. Infection threads were numerous in S-day-old nodules and often were associated with the host cell wall. In several cases, more than one infection thread was found in individual cells. The junction at which the host cell walls converged was often enlarged due to fusion of intracellular branches of infection threads resulting in large infection pockets. The infection threads were made up of a homogeneous, amorphous matrix that enclosed the bacteria. Several finger-like projections were seen radiating from these enlarged infection threads and were delineated from the host cytoplasm by the plasma membrane. As in Azorhizobium caulinodans induced root nodules, the release of Sinorhizobia from the infection threads into the plant cells appears to be mediated by 'infection droplets'. A 15-day­old Sesbania stem nodule revealed typical ultrastructure features of a determinate nodule, containing several bacterioids within symbiosomes.

• The Plant Pathology Journal
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• v.29 no.3
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• pp.285-293
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• 2013

Leaf samples of Solanum lycopersicum, Capsicum annuum, Cucurbita moschata, Cucurbita pepo, Sechium edule and Erythrina spp. were collected. All samples were positive for begomoviruses using polymerase chain reaction and degenerate primers. A sequence of ~1,100 bp was obtained from the genomic component DNA-A of 14 samples. In addition, one sequence of ~580 bp corresponding to the coat protein (AV1) was obtained from a chayote (S. edule) leaf sample. The presence of Squash yellow mild mottle virus (SYMMoV) and Pepper golden mosaic virus (PepGMV) were confirmed. The host range reported for SYMMoV includes species of the Cucurbitaceae, Caricaceae and Fabaceae families. This report extends the host range of SYMMoV to include the Solanaceae family, and extends the host range of PepGMV to include C. moschata, C. pepo and the Fabaceae Erythrina spp. This is the first report of a begomovirus (PepGMV) infecting chayote in the Western Hemisphere.