Yeon-Sik Choo

Plant growth promotion and Penicillium citrinum.

BackgroundEndophytic fungi are known plant symbionts. They produce a variety of beneficial metabolites for plant growth and survival, as well as defend their hosts from attack of certain pathogens. Coastal dunes are nutrient deficient and offer harsh, saline environment for the existing flora and fauna. Endophytic fungi may play an important role in plant survival by enhancing nutrient uptake and producing growth-promoting metabolites such as gibberellins and auxins. We screened roots of Ixeris repenes (L.) A. Gray, a common dune plant, for the isolation of gibberellin secreting endophytic fungi.ResultsWe isolated 15 endophytic fungi from the roots of Ixeris repenes and screened them for growth promoting secondary metabolites. The fungal isolate IR-3-3 gave maximum plant growth when applied to waito-c rice and Atriplex gemelinii seedlings. Analysis of the culture filtrate of IR-3-3 showed the presence of physiologically active gibberellins, GA1, GA3, GA4 and GA7 (1.95 ng/ml, 3.83 ng/ml, 6.03 ng/ml and 2.35 ng/ml, respectively) along with other physiologically inactive GA5, GA9, GA12, GA15, GA19, GA20 and, GA24. The plant growth promotion and gibberellin producing capacity of IR-3-3 was much higher than the wild type Gibberella fujikuroi, which was taken as control during present study. GA5, a precursor of bioactive GA3 was reported for the first time in fungi. The fungal isolate IR-3-3 was identified as a new strain of Penicillium citrinum (named as P. citrinum KACC43900) through phylogenetic analysis of 18S rDNA sequence.ConclusionIsolation of new strain of Penicillium citrinum from the sand dune flora is interesting as information on the presence of Pencillium species in coastal sand dunes is limited. The plant growth promoting ability of this fungal strain may help in conservation and revegetation of the rapidly eroding sand dune flora. Penicillium citrinum is already known for producing mycotoxin citrinin and cellulose digesting enzymes like cellulase and endoglucanase, as well as xylulase. Gibberellins producing ability of this fungus and the discovery about the presence of GA5 will open new aspects of research and investigations.

A quality assurance technique for resistance spot welding using a neuro-fuzzy algorithm

Abstract Resistance spot welding is widely used in the field of plate assembly; however, there is currently no satisfactory nondestructive quality evaluation for this type of welding, either in real time or on-line. Moreover, even though the rate of welding under conditions of expulsion has been high until now, there is still no established method of quality control against expulsion. Accordingly, this paper proposes a quality assurance technique for resistance spot welding using a neuro-fuzzy algorithm. Four parameters from an electrode separation signal, in the case of non-expulsion, and dynamic resistance patterns, in the case of expulsion, are selected as the fuzzy input parameters. These parameters are determined using a neuro-learning algorithm and then are used to construct a fuzzy inference system. When compared with the real strength for the total strength range, the fuzzy inference values of strength produced a specimen error within ±4%, and the percentage of specimen errors within ±1% was 88.8%. The tensile-shear strength limit for electrically coated zinc is 3,920 kN/mm 2 . When evaluating whether the quality of the welding was good or bad according to this criterion, the probability of misjudgment that a good quality weld was a poor one was 0.43%, and the reverse was 2.59%. Finally, the proposed neuro-fuzzy inference system can infer the tensile-shear strength of resistance spot welding with a high efficiency in cases of both non-expulsion and expulsion. It is also anticipated that an on-line welding quality inspection system will be realized in the near future.

Cadophora malorum Cs‐8‐1 as a new fungal strain producing gibberellins isolated from Calystegia soldanella

Fourteen endophytic fungi with different colony morphologies were isolated from the roots of Calystegia soldanella. Endophytic fungi isolated from C. soldanella were identified by internal transcribed spacer (ITS) region. To verify plant growth promotion (PGP), culture filtrates of isolated endophytic fungi were treated in Waito‐c rice (WR) and C. soldanella seedlings. Culture filtrates of Cs‐8‐1 fungal strain had advanced PGP activity. The presence of physiologically bioactive gibberellins (GA) GA1 (1.213 ng ml−1), GA3 (1.292 ng ml−1), GA4 (3.6 ng ml−1), GA7 (1.328 ng ml−1), other inactive GA9 (0.796 ng ml−1) and GA12 (0.417 ng ml−1), GA20 (0.302 ng ml−1), GA24 (1.351 ng ml−1), GA34 (0.076 ng ml−1), and GA53 (0.051 ng ml−1) in culture filtrates of Cs‐8‐1 fungal strain was detected. The Cs‐8‐1 fungal strain was confirmed as a producer of GAs. Molecular analysis of sequences showed high similarity of 99% to Cadophora malorum. Consequentially, the Cs‐8‐1 fungal strain was identified as a new C. malorum producing GAs.

Mutualistic association of Paecilomyces formosus LHL10 offers thermotolerance to Cucumis sativus

We investigated in this study the influence of an endophytic fungus, Paecilomyces formosus LHL10, on the thermotolerance of cucumber (Cucumis sativus) upon exposure to high (38°C) and low (8°C) temperature stresses. The results showed that endophyte-inoculated plants had significantly higher plant growth attributes under high-temperature stress. However, they were either low or insignificant in non-inoculated control and inoculated plants with 8°C treatments. Lower stress-promulgated water deficit and cellular membrane damage were observed in endophyte-treated plants after 38°C treatment than in control plants under 8°C stress. Total polyphenol, reduced glutathione, and lipid peroxidation activities were reduced in endophyte-associated plants after exposure to 38°C as compared with control and 8°C-treated plants. The concentration of saturated fatty acids (palmitic-C16:0; stearic-C18:0) was lower in endophyte-treated plants with or without low-temperature stress, but after 8°C treatment increased compared with controls. Unsaturated fatty acids (oleic-C18:1; linoleic-C18:2; linolenic-C18:3 acids) were similar at normal conditions; however, at 38°C, C18:2 and C18:3 were decreased, and C18:1 was increased in endophyte-treated plants compared with controls, while the inverse relationship was found at 8°C. Low levels of abscisic acid in P. formosus-associated plants after 38°C treatments revealed stress tolerance compared with control and 8°C-treated plants. In contrast, salicylic acid was pronounced in endophyte-treated plants after low-temperature stress as compared to other treatments. The results provide evidence that the response to P. formosus association was beneficial at normal growth temperature and had varying effects in response to temperature stress.

Diversity and Plant Growth-Promotion of Endophytic Fungi Isolated from the Roots of Plants in Dokdo Islands

Endophytic fungi were isolated from the roots of plants growing naturally on the island of Dokdo. Plant samples, such as Miscanthus sinensis, Achyranthus japonica and Echinochloa crusgali were isolated from Dongdo, and those such as Honkenya peploides and Artemsia koidzumii were isolated from Seodo. Twenty one strains of endophytic fungi were isolated from these plants. To identify the strains, PCR (polymerase chain reaction) amplification of the partial ITS (Internal Transcribed Spacer) regions was done with universal primers ITS-1 and ITS-4 to determine the nucleotide sequence of the ITS regions. Of the strains isolated from Miscanthus sinensis, 75% were Penicillium sp. and 25% were Aspergillus sp. Fifty five percent of strains isolated from Achyranthus japonica were Penicillium sp., 30% were Aspergillus sp. and 15% were Zygorhynchus sp. Strains isolated from Echinochloa crusgali were Penicillium sp. (50%), Aspergillus sp. (12%), Giberella sp. (13%), Talaromyces sp. (9%) and Umbelopsis sp. (8%). Of the strains isolated from Honkenya peploides, 76% were Penicillium sp. and 24% were Pestalotiopsis sp. Strains isolated from Artemisia koidzumii were Penicillium sp. (81%) and Mucor sp. (19%). As a result of bioassay, Ec-3-1 strain isolated from Echinochloa crusgalli showed plant growth-promotion activity. Of all the endophytic fungi isolated, Penicillium sp. was the most abundantly distributed fungal strain in all plants used in this study.

Effects of Endophytic Fungal Secondary Metabolites on the Growth and Physiological Response of Carex kobomugi Ohwi

Abstract Recently, plant growth–promoting endophytic fungi with gibberellins-producing ability were isolated from the roots of coastal sand dune plants. Carex kobomugi Ohwi in coastal sand dunes was treated with the supernatant solution of Penicillium citrinum KACC43900 isolated from Ixeris repens (L.) A. Gray. After treatment, the length of leaf blades, photosynthesis, chlorophyll fluorescence, and soil respiration were measured in the field. The contents of chlorophyll and carotenoid were determined with leaf blades selected for measurement of chlorophyll fluorescence. Fungal culture filtrate (FCF) increased leaf blade length, the contents of chlorophyll a (Chl a) and chlorophyll b (Chl b), total chlorophyll (total Chl [a + b]), and carotenoid in leaf blades of C. kobomugi. FCF also increased net photosynthetic rate (A), transpiration rate (E), carboxylation efficiency (A/Ci), and water-use efficiency (A/E). However, the ratio of variable fluorescence to maximal fluorescence (Fv/Fm) did not show significant difference between control and FCF-treated plants. Soil respiration rates were higher in the site treated with FCF than the control. Although growth response and physiological characteristics of C. kobomugi were different according to the treatment methods of FCF, injection or spray treatment, plant growth of C. kobomugi was increased with FCF treatment.

Diversity and Plant Growth Promoting Capacity of Endophytic Fungi Associated with Halophytic Plants from the West Coast of Korea

Abstract Five halophytic plant species, Suaeda maritima, Limonium tetragonum, Suaeda australis, Phragmites australis, and Suaeda glauca Bunge, which are native to the Muan salt marsh of South Korea, were examined for fungal endophytes by sequencing the internal transcribed spacer (ITS) region containing ITS1, 5.8S rRNA, and ITS2. In total, 160 endophytic fungal strains were isolated and identified from the roots of the 5 plant species. Taxonomically, all 160 strains belonged to the phyla Ascomycota, Basidiomycota, and Zygomycota. The most dominant genus was Fusarium, followed by the genera Penicillium and Alternaria. Subsequently, using 5 statistical methods, the diversity indices of the endophytes were determined at genus level. Among these halophytic plants, P. australis was found to host the greatest diversity of endophytic fungi. Culture filtrates of endophytic fungi were treated to Waito-C rice seedlings for plant growth-promoting effects. The fungal strain Su-3-4-3 isolated from S. glauca Bunge provide the maximum plant length (20.1 cm) in comparison with wild-type Gibberella fujikuroi (19.6 cm). Consequently, chromatographic analysis of the culture filtrate of Su-3-4-3 showed the presence of physiologically active gibberellins, GA1 (0.465 ng/mL), GA3 (1.808 ng/mL) along with other physiologically inactive GA9 (0.054 ng/mL) and GA24 (0.044 ng/mL). The fungal isolate Su-3-4-3 was identified as Talaromyces pinophilus.

Isolation of Endophytic Fungi Capable of Plant Growth Promotion from Monocots Inhabited in the Coastal Sand Dunes of Korea

Endophytic fungi predominantly inhabit grasses, and produce a variety of beneficial metabolites for plant growth, as well as help their hosts against pathogens and herbivores. Current study was focused on plant growth promoting activity of endophytic fungi inhabited in the roots of sand dune grasses. We collected 49 fungal isolates from the roots of four most common sand dune grasses and screened them for their growth promoting capacity. Results showed that 37 fungal isolates (75.5%) promoted plant height and shoot length of waito-c rice, 11 fungal isolates (22.5%) suppressed it, while 1 fungus (2%) showed no effect on the growth attributes. The fungal strain Gibberella fujikuroi, along with distilled water and Czapek broth medium, were taken as control for this experiment. It was concluded that a major proportion of endophytic fungi inhabited in the sand dune plants produce metabolites, and thus help in growth and development of the host plant.

Mineral ion, nitrogen and organic solute pattern in sedges(Carex Spp.) – a contribution to the physiotype concept. I. Field samples

Summary Fifty species of Carex from different Austrian habitats have been investigated to elucidate their physiological plasticity with respect to different ecological conditions. The plants were collected in their natural habitats and divided into five ecological groups according to the respective soils (silicate soil, limestone, serpentine, flysch-sandstone, saline soil). Inorganic ions, organic acids, low molecular weight carbohydrates (sugars and sugar alcohols), amino acids, betaines and total N were measured quantitatively together with selected inorganic soil characteristics. No substantial differences could be found in the solute patterns between saline, dry and wet conditions. In particular, proline, betaines and sugar alcohols – known to act as “compatible solutes” or “cytoplasmic osmotica” in several salt- or water-stressed plants – were not accumulated in Carex species growing under conditions of low soil water potential. In addition, physiological data were subjected to cluster analysis. With reference to the chosen parameters, the investigated species could not be assigned to the five ecological groups and showed no considerable physiological plasticity. Thus, the genus represents a homogeneous “physiotype” showing high K/Ca ratios as well as high contents of mono- and disaccharides and γ-aminobutyric acid. K and sugars are the main osmotic solutes in Carex species. Concerning organic acids, mainly citrate, malate and malonate are involved in balancing excess cation uptake. It is concluded that the ecological success of the genus Carex may be largely attributable to an excellent regulation of the ion uptake processes as well as ion balance within cells.

Culturable Fungal Endophytes Isolated from the Roots of Coastal Plants Inhabiting Korean East Coast

Abstract Twelve plant species were collected from the east coast of Korea to identify culturable endophytes present in their roots. The fungal internal transcribe spacer (ITS) region (ITS1-5.8SrRNA-ITS2) was used as a DNA barcode for identification of fungi. A total of 194 fungal strains were identified and categorized into 31 genera. The genus Penicillium accounted for the largest number of strains, followed by the genus Aspergillus. Furthermore, using 5 statistical methods, the diversity indices of the fungi were calculated at the genus level. After comprehensive evaluation, the endophytic fungal group from Phragmites australis ranked highest in diversity analyses. Several strains responsible for plant growth and survival (Penicillium citrinum, P. funiculosum, P. janthinellum, P. restrictum, and P. simplicissimum), were also identified. This study provides basic data on the sheds light on the symbiotic relationship between coastal plants and fungi.