Evaluation of Barley and Wheat Germplasm for Resistance to Head Blight and Mycotoxin Production by Fusarium asiaticum and F. graminearum.

Fusarium head blight (FHB) is one of the most serious diseases in barley and wheat, as it is usually accompanied by the production of harmful mycotoxins in the grains. To identify FHB-resistant breeding resources, we evaluated 60 elite germplasm accessions of barley (24) and wheat (36) for FHB and mycotoxin accumulation. Assessments were performed in a greenhouse and five heads per accession were inoculated with both Fusarium asiaticum (Fa73, nivalenol producer) and F. graminearum (Fg39, deoxynivalenol producer) strains. While the accessions varied in disease severity and mycotoxin production, four wheat and one barley showed <20% FHB severity repeatedly by both strains. Mycotoxin levels in these accessions ranged up to 3.9 mg/kg. FHB severity was generally higher in barley than in wheat, and Fa73 was more aggressive in both crops than Fg39. Fg39 itself, however, was more aggressive toward wheat and produced more mycotoxin in wheat than in barley. FHB severity by Fa73 and Fg39 were moderately correlated in both crops (r = 0.57/0.60 in barley and 0.42/0.58 in wheat). FHB severity and toxin production were also correlated in both crops, with a stronger correlation for Fa73 (r = 0.42/0.82 in barley, 0.70 in wheat) than for Fg39.

First Report of Verticillium dahliae causing Verticillium Wilt on Radish in South Korea.

Radish (Raphanus sativus L.) is an important crop grown in Korea primarily for its use in kimchi, and is cultivated on an area of about 23,000ha. In September 2016, radish leaves were observed with yellowing and wilting symptoms in Gangneung (37.55406°N, 128.84871°E) and Jeongseon (37.42895°N, 128.85882°E), Gangwon province, South Korea. Disease incidence was estimated at approximately 10% in two fields, respectively. About 30% of radish plants (cv. Gwangdongyeoreum) with foliar symptoms exhibited vascular discoloration in the roots. Small pieces of discolored root tissue were surface sterilized in 1% NaOCl for 30s, and then rinsed in sterile water. The tissue pieces were placed on water agar and incubated at 25°C for 10 days. Eight isolates were obtained through single spore isolation, and a representative isolate NC16557 (from Gangneung) was selected for identification. After 14 days, colonies on potato dextrose agar (PDA) were 3.7 cm in diameter and becoming dark due to the formation of microsclerotia. Aerial hyphae were smooth-walled, 3 to 4 µm wide. Conidiophores were erect or slanted, verticillately branched or unbranched, and hyaline. Conidia were hyaline, smooth-walled, non-septate, cylindrical to oval, 4.8 to 6.6 × 2.6 to 3.4 µm (mean 5.7 × 2.9 µm, l/w =2.0, n =80). Microsclerotia were immersed in the agar, composed of rounded, brown-pigmented cells and elongate or irregular in shape, 42 to 60 µm diam. Based on morphology, NC16557 isolate was tentatively identified as Verticillium dahliae (Hawksworth and Talboys, 1970; Isaac, 1967). To confirm taxonomic placement, DNA extracted from mycelia of the same isolate was PCR amplified and sequenced targeting internal transcribed spacer (ITS) regions of rDNA, translation elongation factor 1 alpha (TEF), actin (ACT), tryptophan synthase (TS), and glyceraldehyde-3-phosphate dehydrogenase (GPD) genes (Inderbitzin et al., 2011). The sequences were deposited in GenBank with accession numbers MZ723402, and MZ735720-MZ735723, respectively. The sequencing results showed 100% (ITS=479/479, TEF=500/500, ACT=185/185, and TS=295/295) and 99.61% (GPD=257/258) similarity with the sequences of V. dahlia type strain PD322 (LR026889, HQ414624, HQ206921, HQ414909, and HQ414719) by BLAST. Based on the morphology and multigene sequence analysis, the isolate was identified as V. dahliae. Pathogenicity of two isolates (NC16557 and NC16547) was carried out in the greenhouse using ten 10-day-old seedlings (cv. Gwangdongyeoreum) by root-tip cutting and then soaking the roots in a fungal spore suspension of 106 conidia mL-1 for 1 hour. Ten seedlings were treated with sterile distilled water as a control. All plants were placed in the greenhouse at 15°C (night)/25°C (day) with natural light. After 6 weeks, all inoculated plants showed vascular discoloration in the roots while control plants remained asymptomatic. However, the above-ground symptoms of inoculated plants, such as yellowing and wilting, were indistinguishable from control plants. V. dahliae was consistently re-isolated from the symptomatic root tissues and the pathogen identity was confirmed by observing morphological characteristics. Verticillium wilt of radish has been reported from China(Yan et al., 2019). In Korea, this is the first report that V. dahliae causes Verticillium wilt of radish, although Dumin et al. (2020) already reported on Verticillium wilt of Chinese cabbage in Gangwon province, the main production area of Chinese cabbage and radish in summer. With these findings in Chinese cabbage and now radish, it will be critical to identify or develop Verticillium-resistant varieties and other management strategies for the stable production of these crops in Korea.

Characterization of Nivalenol-Producing Fusarium asiaticum That Causes Cereal Head Blight in Korea.

Fusarium asiaticum of the F. graminearum species complex causes head blight in small-grain cereals. The nivalenol (NIV) chemotypes of F. asiaticum is more common than the deoxynivalenol (DON) chemotypes of F. asiaticum or F. graminearum in Korea. To understand the prevalence of F. asiaticum-NIV in Korean cereals, we characterized the biological traits of 80 cereal isolates of F. asiaticum producing NIV or 3-acetyl-deoxynivalenol (3-ADON), and 54 F. graminearum with 3-ADON or 15-acetyl-deoxynivalenol (15-ADON). There was no significant difference in mycelial growth between the chemotypes, but F. asiaticum isolates grew approximately 30% faster than F. graminearum isolates on potato dextrose agar. Sexual and asexual reproduction capacities differed markedly between the two species. Both chemotypes of F. graminearum (3-ADON and 15-ADON) produced significantly higher numbers of perithecia and conidia than F. asiaticum-NIV. The highest level of mycotoxins (sum of trichothecenes and zearalenone) was produced by F. graminearum-3-ADON on rice medium, followed by F. graminearum-15-ADON, F. asiaticum-3-ADON, and F. asiaticum-NIV. Zearalenone levels were correlated with DON levels in some chemotypes, but not with NIV levels. Disease assessment on barley, maize, rice, and wheat revealed that both F. asiaticum and F. graminearum isolates were virulent toward all crops tested. However, there is a tendency that virulence levels of F. asiaticum-NIV isolates on rice were higher than those of F. graminearum isolates. Taken together, the phenotypic traits found among the Korean F. asiaticum-NIV isolates suggest an association with their host adaptation to certain environments in Korea.

Optimal CT scanning parameters for commonly used tumor ablation applicators.

PURPOSE: CT-beam hardening artifact can make tumor margin visualization and its relationship to the ablation applicator tip challenging. To determine optimal scanning parameters for commonly-used applicators. MATERIALS AND METHODS: Applicators were placed in ex-vivo cow livers with implanted mock tumors, surrounded by bolus gel. Various CT scans were performed at 440mA with 5mm thickness changing kVp, scan time, ASiR, scan type, pitch, and reconstruction algorithm. Four radiologists blindly scored the images for image quality and artifact quantitatively. RESULTS: A significant relationship between probe, kVp level, ASiR level, and reconstruction algorithm was observed concerning both image artifact and image quality (both p=<0.0001). Specifically, there are certain combinations of kVp, ASiR, and reconstruction algorithm that yield better images than other combinations. In particular, one probe performed equivalently or better than any competing probe considered here, regardless of kVp, ASiR, and reconstruction algorithm combination. CONCLUSION: The findings illustrate the overall interaction of the effects of kVp, ASiR, and reconstruction algorithm within and between probes, so that radiologists may easily reference optimal imaging performance for a certain combinations of kVp, ASiR, reconstruction algorithm and probes at their disposal. Optimum combinations for each probe are provided.

Accuracy of the CT numbers of simulated lung nodules imaged with multi-detector CT scanners.

A study was performed to determine the accuracies and reproducibilities of the CT numbers of simulated lung nodules imaged with multi-detector CT scanners. The nodules were simulated by spherical balls of three diameters (4.8, 9.5, and 16 mm) and two compositions (50 and 100 mg/cc CaCO3 in water-equivalent plastic). All were scanned in a liquid-water-filled container at the center of a water-equivalent-plastic phantom and in air cavities within the same phantom using GE multi-detector CT scanners. The nodules were also scanned within simulated lung regions in an anthropomorphic thorax section phantom that was bolused on both sides with water-equivalent slabs. Results were compared for three scanning protocols--the protocol for the National Lung Screening Trial (NLST), the protocol for the Lung Tissue Research Consortium (LTRC) study, and a high resolution (small pitch, thin slice and small scan interval) higher dose "gold standard" protocol. Scans were repeated three times with each protocol to assess reproducibility. The CT numbers of the nodules in water were found to be nearly independent of nodule size. However, the presence and the size of an air cavity surrounding a nodule had a significant effect (e.g., the CT number of a 50 mg/cc nodule was 64 HU in water, 37 HU in a 1.8 cm diameter air cavity, and 19 HU in a 4.4 cm diameter air cavity). This variability of CT number with size of air cavity may affect the results of the LTRC study in which patients are scanned at both full inspiration and full expiration. The CT numbers of the 9.5 and 16 mm diameter nodules within the anthropomorphic phantom were highly reproducible (average standard deviations of 2 HU or less) for all protocols. On the other hand, both accuracy and reproducibility were significantly degraded for the 4.8 mm diameter nodules, especially for the NLST (2.5 mm thickness, 2 mm slice interval) technique. Use of thinner slice (1.25 mm) and slice interval (1.25 mm) scans that can be reconstructed retrospectively from the multi-detector helical CT projection data of the standard NLST protocol yield CT numbers for the 4.8 mm diameter nodules that are more accurate and reproducible than those of the standard NLST technique. In general, the CT numbers of the nodules were found to be lower at positions near the centers of the lungs and near the spine, which is probably due to increased beam hardening in those regions. Also, larger nodules were found to have higher CT numbers than smaller nodules, consistent with results obtained on early single slice GE CT scanners. Until manufacturers develop quantitative CT scanners with improved x-ray beam hardening and scatter corrections, it is recommended that reference phantoms be employed to more accurately assess the calcium contents of patient lung nodules in screening and tissue characterization studies and in eventual computer-aided detection and diagnosis applications.