Development of Rapid Detection Methods for Fusarium oysporum f. sp. melonis in Melon Seeds

Melon (Cucumis melo L.) is a global commercial crop that is sensitive to seed-borne wilt infections caused by Fusarium oxysporum f. sp. melonis (Fom). To address the challenge of detecting Fom contamination, we designed a probe-based real-time PCR method, TDCP2, in combination with rapid or column-based DNA extraction protocols to develop reliable molecular detection methods. Utilizing TDCP2, the detection rate reached 100% for both artificially Fom-inoculated (0.25-25%) and pod-inoculated melon seeds in conjunction with DNA samples from either the rapid or column-based extraction protocol. We performed analyses of precision, recall, and F1 scores, achieving a maximum F1 score of 1 with TDCP2, which highlights the robustness of the method. Additionally, intraday and interday assays were performed, which revealed the high reproducibility and stability of column-based DNA extraction protocols combined with TDCP2. These metrics confirm the reliability of our developed protocols, setting a foundation for future enhancements in seed pathology diagnostics and potentially broadening their applicability across various Fom infection levels. In the future, we hope that these methods will reduce food loss by improving the control and management of melon diseases.

First report of leaf brown blight caused by Neopestalotiopsis formicarum on jabuticaba in Taiwan

Jabuticaba (Plinia cauliflora (Mart.) Kausel) was originated from Brazil (Lorenzi 2000). The production of jabuticaba is growing globally as its value in the food and pharmaceutical industries (Benvenutti 2021). In August 2019, jabuticaba plants with symptoms of leaf blight were observed in the field at the Meinong of Kaohsiung City, Taiwan. Disease incidence was 40%. Symptoms first presented as small, water-soaked lesions on young leaves, and then dark brown lesions of 1-3 cm in diameter on mature leaves. Six symptomatic leaves were collected from 6 jabuticaba plants for verifying the causal agents. Tissues (5 × 5 mm2) were cut from the margin of symptomatic leaf. Samples were sterilized in 1% sodium hypochlorite for 60 s, rinsed with sterile distilled water three times and then placed in 1% water agar in the dark for 5 days at room temperature. Resultant fungal colonies were purified by subculturing fungal hyphal tips on potato dextrose agar in a growth chamber (28°C, 12 h photoperiod) until fungal conidia appeared. The fungi initially produced white, cottony, aerial mycelium, after which concentric black conidiomata appeared on the plates after 7 days of incubation. The 5-celled conidia were fusiform to ellipsoid, straight to slightly curved, with sizes of 24.00-44.00 µm × 6.00-13.00 µm (avg. size, 32.00 × 9.37 µm, n = 120). The apical and basal cells were hyaline, and 3 median cells were pale brown and versicolorous. Conidia had 2-3 apical appendages and a conical basal cell with a truncate base. Based on the characteristics, which were common among isolates from diseased samples, the causal pathogen was identified as Neopestalotiopsis sp. (Solarte et al. 2018). Internal transcribed spacer (ITS), translation elongation factor 1α (TEF), β-tubulin, and large ribosomal subunit (LSU) DNA sequences were obtained from these isolates and deposited in GenBank (MN723897, ITS; MN813055, TEF; MN813054, β-tubulin; MN860104, LSU). Sequences demonstrated high sequence identity with those of Neopestalotiopsis formicarum ex-type cultures CBS 362.72 (Maharachchikumbura et al. 2014): 99.44% for ITS (KM199358), 99.38% for TEF (KM199517), 98.86% for β-tubulin (KM199455), and 100.00% for LSU (KM116248). The phylogenetic relationship in Neopestalotiopsis species supported the identification of our isolates as N. formicarum. Three independent 3-isolate inoculation experiments were performed to fit Koch's postulates. Surface-sterilized leaves on live plants were punctured with a needle and inoculated with 5 µL of conidial suspension (1 × 105 conidia/mL). Inoculated plants were kept in a growth chamber (25°C, 70% relative humidity) for 7 days. Control plants were inoculated with sterile distilled water and kept under the same conditions. Inoculated leaves developed brown lesions around wounds after seven days. The pathogen was re-isolated from diseased plants, following the steps used for the original procedure, with identical characteristics as the initial isolates. This is the first report of leaf brown blight caused by N. formicarum on jabuticaba in Taiwan. N. formicarum was recently considered as a new threat to jabuticaba (Gualberto et al. 2021). In addition, it has a broad host range on many tropical crops, such as guarana and banana (Gualberto et al. 2021). Neopestalotiopsis spp. have been reported to cause important economic fruit diseases (Gualberto et al. 2021). Therefore, N. formicarum may become the potential risk for fruit production of tropical crops.

Molecular Detection Assays for Rapid Field-Detection of Rice Sheath Blight

Rhizoctonia solani (Rs), a soil-borne fungal pathogen, can result in rice sheath blight (ShB), which causes yield loss. To prevent outbreaks of ShB and enhance the sustainability of rice production, it is critical to develop a rapid ShB detection method for specific, fast, and on-site disease management. In this study, a reagent for the rapid extraction of this pathogen was developed for on-site detection. The specificity and sensitivity of a novel SMS RS1-F/SMS RS1-R primer set and a ITS1/GMRS-3 reference primer set were tested, while four different extraction protocols for ShB were developed. Moreover, intraday and interday assays were performed to evaluate the reproducibility of the detection methods developed. The results indicated that all of the developed protocols are suitable for use in detecting ShB. In addition, all the samples of infected rice yielded positive Rs detection results when subjected to TaqMan probe-based real-time PCR and SYBR green-based real-time PCR (SMS RS1-F/SMS RS1-R) tests in which automatic magnetic bead-based DNA extraction was performed. These results indicated that the two molecular detection protocols were suitable for the field diagnosis of ShB for all asymptomatic and symptomatic rice samples.

Deciphering the origin of Aspergillus flavus NRRL21882, the active biocontrol agent of Afla-Guard®

Single nucleotide polymorphisms (SNPs) of genome sequences of eight Aspergillus flavus and seven Aspergillus oryzae strains were extracted with Mauve, a multiple-genome alignment programme. A phylogenetic analysis with sequences comprised of concatenated total SNPs by the unweighted pair group method with arithmetic mean (UPGMA) of MAFFT adequately separated them into three groups, A. flavus S-morphotype, A. flavus L-morphotype and A. oryzae. Divergence time inferred for A. flavus NRRL21882, the active agent of the biocontrol product Afla-Guard^® , and S-morphotype was about 5·1 mya. Another biocontrol strain, A. flavus AF36, diverged from aflatoxigenic L-morphotype about 2·6-3·0 mya. Despite the close relatedness of A. oryzae to A. flavus, A. oryzae strains likely evolved from aflatoxigenic Aspergillus aflatoxiformans (=A. parvisclerotigenus). A survey of A. flavus populations implies that prior Afla-Guard^® applications are associated with prevalence of NRRL21882-type isolates in Mississippi fields. In addition, a few NRRL21882 relatives were identified. A. flavus Og0222, a biocontrol ingredient of Aflasafe™, was verified as a NRRL21882-type strain, having identical sequence breakpoints that led to deletion of aflatoxin and cyclopiazonic acid gene clusters. A similar UPGMA analysis suggests that the occurrence of NRRL21882-type strains is a more recent event.

First report of anthracnose caused by Colletotrichum fructicola on tea in Taiwan

Tea (Camellia sinensis (L.) O. Kuntze) is a very popular beverage and cash crop that is widely cultivated in tropical and subtropical areas. In November 2017, diseased tea plants that exhibiting brown blight disease were observed in Guanxi Township of Hsinchu County in Taiwan. In the plantation,15% of tea trees (about 4000 plants) had an average of 20% of the leaves with at least one lesion. The symptoms began as small, water-soaked lesions on young leaves and twigs and later became larger, dark brown, necrotic lesions of 1 to 3 cm in diameter on leaves and 2 to 5 cm in length on twigs. Symptomatic leaf tissue (1 cm2) from five samples per sample) was surface sterilized with 1% NaClO (from commercial bleach, Clorox) for 1 min, washed with sterilized water 3 times, plated onto potato dextrose agar (PDA), and incubated under 12h/12h cycles of light and darkness at 25°C until sporulation to determine the causal agent. A fungus was consistently isolated from symptomatic leaf samples (80% isolation rate). The fungus initially produced white-to-gray fluffy aerial hyphae, which subsequently exhibited dark pigmentation. Acervuli and setae were absent. The conidia were hyaline, aseptate, smooth-walled, and cylindrical with obtuse to slightly rounded ends, with sizes of 12.10 to 16.02 × 3.58 to 4.91 (average 13.77 × 4.05, n = 30) μm. The majority had two rounded guttules. The appressoria were brown to dark brown, ovoid and slightly obtuse at the tip in shape, had lengths ranging from 3.59 to 10.31 μm (with an average of 7.18 μm, n = 30), and had diameters of 3.14 to 6.43 μm (with an average of 5.10 μm, n = 30). Morphological characteristics matched the descriptions of Colletotrichum fructicola (Liu et al. 2015; Fuentes-Aragón et al. 2018). The internal transcribed spacer of nuclear ribosomal DNA (ITS), actin (ACT), chitin synthase (CHS-1), and Apn2-Mat1-2 intergenic spacer and partial mating-type Mat1-2 gene (ApMAT) sequences of the isolates were obtained to confirm this identification. The sequences showed close identity with those of C. fructicola ex-type cultures ICMP18581 and CBS 130416 (Weir et al. 2012) of 99.65% for the ITS (JX010165), 99.29% for the ACT (JX009501), and 100.00% for the CHS-1 (JX009866), as well as close identity with the other ex-type culture LF506 (Liu et al. 2015) of 99.59% for the ApMat (KJ954567), supporting the isolate's identification as C. fructicola. The sequences were deposited in GenBank, with the following accession Nos.: MN608177 (ITS), MN393175 (ACT), MT087546 (CHS-1), and MT087542 (ApMAT). Based on morphology and DNA sequence analysis, the associated fungus was identified as C. fructicola. Pathogenicity tests were performed next according to the procedures described in Chen et al. (2017). Healthy leaves on tea plants (Ca. sinensis 'Chin-shin Oolong') were wounded by pinpricking in the middle of each counterpart and inoculated with conidial suspension (1 × 107 conidia/ml, 10 μl). Both non-wounded and wounded healthy leaves were inoculated with the conidial suspension and sterile distilled water (a water control). The tea plants were covered with plastic bags to maintain high relative humidity for two days. One week after inoculation, anthracnose was observed on 40% of inoculated leaves, whereas all the control leaves remained healthy. The fungus was re-isolated from the diseased plants, and identified as C. fructicola by resequencing of the four genes. To the best of our knowledge, this is the first report of anthracnose caused by C. fructicola on tea in Taiwan although the pathogen has been present in China and Indonesia (Wang et al. 2016; Shi et al. 2017; Farr and Rossman, 2020).

Development of a TaqMan Probe-Based Insulated Isothermal Polymerase Chain Reaction (iiPCR) Assay for Detection of Fusarium oxysporum f. sp. cubense Race 4

This study developed a novel and inexpensive detection method based on a TaqMan probe-based insulated isothermal polymerase chain reaction (iiPCR) method for the rapid detection of Panama disease caused by Fusarium oxysporum f. sp. cubense (Foc) race 4, which is currently among the most serious fungal vascular diseases worldwide. By using the portable POCKIT™ device with the novel primer set iiFoc-1/iiFoc-2, the Foc race 4 iiPCR assay (including DNA amplification and signal monitoring) could be completed within one hour. The developed Foc race 4 iiPCR assay is thus a user-friendly and efficient platform designed specifically for the detection of Foc race 4. The detection limit of this optimized Foc iiPCR system was estimated to be 1 copy of the target standard DNA as well as 1 fg of the Foc genomic DNA. This approach can serve as a rapid detection method for in planta detection of Foc race 4 in field-infected banana. It was concluded that this molecular detection procedure based on iiPCR has good potential for use as an efficient detection method.

Tuberculosis mortality trends in Taiwan: a resurgence of non-respiratory tuberculosis

SETTING

Population-based study in Taiwan.

OBJECTIVE

To determine the tuberculosis (TB) mortality trends in Taiwan by site and age.

DESIGN

Mortality data for the years 1972 to 2001 were used to calculate the age/site-specific mortality rate (deaths per 100000 population). The year of change in the slope of mortality trends was estimated by iterative piecewise regression analysis.

RESULTS

A levelling off in mortality trends was noted in the late 1980s for all age groups except those aged 75 and above. Except in the age group 25-44 years, the trends in respiratory TB mortality showed a smooth decline. However, for non-respiratory TB mortality, a reversal of the decline was noted for all age groups since 1994-1995. A twofold increase in the number of deaths from central nervous system (CNS) and 'other' TB was noted. A marked increase in the number of deaths from old TB was noted since 1992-1996.

CONCLUSION

TB mortality trends in Taiwan have not declined as expected over the past decade. The slowing down of the decline in TB mortality was mainly attributable to a levelling off of respiratory TB mortality in the age group 25-44 and a reversal of non-respiratory TB mortality trends, especially in the 25-44 and > or =65 years age groups.

Chromosomal organization of amplified genes in multidrug-resistant Chinese hamster cells

Six independently derived multidrug-resistant Chinese hamster cell lines selected with vincristine, daunorubicin, actinomycin D, or colchicine were probed by in situ hybridization techniques with the cloned cDNA, p5L-18, to chromosomally localize known or presumed amplified P-glycoprotein genes. One or two clusters of amplified genes were demonstrable in all of the highly resistant sublines and were localized to homogeneously staining regions and/or abnormally banding regions, gene amplification-associated cytogenetic abnormalities, on eight different chromosomes. Analysis of trypsin-Giemsa banded karyotypes revealed additional, multiple chromosomal rearrangements that were apparently nonspecific. Mapping studies localized the native P-glycoprotein gene(s) to the region q23 to 31 (most probably band 26) on the long arm of chromosome 1 of normal Chinese hamster bone marrow fibroblasts and normal chromosome 1 homologues in resistant cells. Southern blot analysis of restriction endonuclease fragments indicated the amplification of one or both of (at least) two wild-type nonallelic genes in four of the lines and the presence in one line (DC-3F/DMM XX) of a unique 5.0-kilobase BamHI fragment resulting from a recombinational event during amplification. Comparison with the cytogenetic data indicated no correlation between restriction patterns generated by EcoRI, HindIII, PstI, or BamHI and chromosomal location of amplified genes. However, the only sublines in which the homogeneously staining region or abnormally banding region is positioned at 1q26 (at or near the site of the native gene) exhibit either alterations in gene structure (DC-3F/DM XX) or in regulation of gene expression (DC-3F/AD X), suggesting a process more complex than simply amplification of the gene in loco.

Sorcin (V19), a soluble acidic calcium-binding protein overproduced in multidrug-resistant cells. Identification of the protein by anti-sorcin antibody

Sorcin (soluble resistance-related calcium-binding protein), an acidic (pI = 5.7) protein (Mr approximately 20 kDa) previously designated V19, was originally identified in cells selected for high levels of resistance to vincristine. Two-dimensional gel electrophoresis and/or Western blot techniques now show sorcin to be overproduced in cells selected for resistance to actinomycin D (QUA/ADj), colchicine (CHRC5), and adriamycin (BE(2)-C/ADR). Not all cell lines selected for resistance to these drugs overproduced sorcin; e.g. cells of an independently selected actinomycin D-resistant subline of QUA, QUA/ADsx, did not contain increased amounts of sorcin. Sorcin was purified by preparative gel electrophoresis from QUA/ADj cells and used to generate specific antiserum in chickens. By Western blot analyses the antiserum was shown to recognize sorcin in QUA/ADj and in vincristine-resistant mouse and Chinese hamster lung, colchicine-resistant Chinese hamster ovary, and adriamycin-resistant human neuroblastoma lines. Low level expression of the protein was detectable in control, drug-sensitive cells. Direct binding assays with 45Ca2+ showed that sorcin was a calcium-binding protein. QUA/ADj cells contained increased numbers of double minute chromosomes (DMs), cytogenetic indicators of gene amplification. As found for two other multidrug-resistant sublines, sorcin overproduction in QUA/ADj cells may be the result of amplification of the sorcin-encoding gene. The overproduction of this protein in multidrug-resistant cells of various species implies that sorcin plays a role in expression of the resistant phenotype.

Gene amplification-associated cytogenetic aberrations and protein changes in vincristine-resistant Chinese hamster, mouse, and human cells

We carried out cytogenetic studies of four Chinese hamster, mouse, and human cell lines selected for high levels of resistance (500- to 4,000-fold) to vincristine (VCR) by a multistep selection procedure. All cells examined contained gene amplification-associated metaphase chromosome abnormalities, either homogeneously staining regions (HSRs), abnormally banding regions (ABRs), or double-minute chromosomes (DMs); control actinomycin D- and daunorubicin-resistant hamster lines did not exhibit this type of chromosomal abnormality. VCR-resistant Chinese hamster sublines exhibited both increased synthesis of the protein V19 (Mr 19,000; pl = 5.7) and increased concentrations of V19 polysomal mRNA. When VCR-resistant cells were grown in drug-free medium, level of resistance, synthesis of V19, and amount of V19 mRNA declined in parallel with mean length of the HSR or mean number of DMs per cell. Cross-resistance studies indicate that VCR-resistant cells have increased resistance both to antimitotic agents and to a wide variety of agents unrelated to VCR in chemical structure and/or mechanism of action. Our studies of tubulin synthesis in Chinese hamster cells indicate no overproduction of tubulin or presence of a mutant tubulin species. Comparison with antifolate-resistant Chinese hamster cells known to contain amplified dihydrofolate reductase genes localized to HSRs or ABRs strongly suggests that the HSRs, ABRs, or DMs of the Vinca alkaloid-resistant sublines likewise represent cytological manifestations of specifically amplified genes, possibly encoding V19, involved in development of resistance to VCR.

Drug resistance in Chinese hamster lung and mouse tumor cells

Studies of Chinese hamster and mouse cells with high levels of acquired resistance to dactinomycin, daunorubicin, or vincristine have shown that these different permeability mutants all display similar phenotypic alterations: dramatic changes toward normal cell morphology and growth behavior and substantially reduced oncogenic potential. All three resistant cell types show increased expression of a high molecular weight plasma membrane glycoprotein species, gp150. Uniquely, vincristine-resistant cells contain gene amplification-associated chromosome abnormalities (homogeneously staining regions or double minute chromosomes), and they oversynthesize a low molecular weight cytosolic protein (V19). Cells grown in the absence of drug are phenotypically unstable. Revertant cells decline in resistance, length or number of homogeneously staining regions or double minute chromosomes, and expression of gp150 and V19. These proteins are thus candidate products of amplified genes which may or may not be manifested cytogenetically. The phenomena of drug resistance and reverse transformation are currently being addressed in protein phosphorylation studies.

Chronotropic responses of human heart tissue cultures

Three presumptive cardiac tissues from aborted human embryos which ranged in length from 2 mm to 4 mm and in age from 53 days to 71 days were maintained in culture beating rhythmically for 18-88 days. Medium renewal, temperature increases (from 31° to 38°C), and pH increases (from 6.92 to 7.75) raised the pulsation rate. Excess potassium stopped the pulsation. Sympathomimetic drugs increased the pulsation rate, and this action was blocked by the beta-receptor inhibitor, propranolol, suggesting the presence of functioning beta-receptor sites in the heart cells by the end of the second month of development.

The establishment and chromosome analysis of a new cell line of Chinese hamster from spontaneous transformation in vitro

A male Chinese hamster cell line has been established through spontaneous transformation in a skin culture. Chromosome studies at passage 13 revealed one major and one minor type of pseudodiploid cells (77.3 and 20%). At passage 42, only the major subline persisted (78%). The two sublines, especially the major one, had selective advantage over other cell types in this cell line probably because they were more nearly genetically balanced. Autoradiographic studies indicated no overall increase in late replicating chromosomal elements in the two sublines. Both cell types lacked the X chromosome and chromosome 6, but they were largely compensated for by the presence of new marker chromosomes. However, more chromosomal material was missing in the minor type than in the major type, and this may account for the lower adaptability of the former.

Selection for trisomic cells in a mosaic fibroblast culture

In a human mosaic fibroblast culture consisting of a diploid cell line, 46, XY, t(Cp+;Dq–), and a trisomic cell line, 47, XY, D+, t(Cp+;Dq–), the frequency of trisomic cells initially decreased from 74% to 48% and then increased steadily through successive passages, until finally all diploid cells disappeared. The gradual predominance of trisomic cells coincided with the degenerative phase of the culture. It is speculated that although the genetically balanced diploid cells competed well in the beginning, they started their senescence earlier, thus giving way to the genetically unbalanced trisomic cells. Perhaps the same selective advantage of aneuploid cells over diploid cells could be shown in other mosaic cell cultures if they are maintained for longer periods.