Insights into Grape Ripe Rot: A Focus on the Colletotrichum gloeosporioides Species Complex and Its Management Strategies.

Grape ripe rot, which is predominantly caused by the Colletotrichum species, presents a growing threat to global grape cultivation. This threat is amplified by the increasing populations of the Colletotrichum species in response to warmer climates. In this review, we investigate the wide-ranging spectrum of grape ripe rot, specifically highlighting the role and characteristics of the C. gloeosporioides species complex (CGSC). We incorporate this understanding as we explore the diverse symptoms that lead to infected grapevines, their intricate life cycle and epidemiology, and the escalating prevalence of C. viniferum in Asia and globally. Furthermore, we delve into numerous disease management strategies, both conventional and emerging, such as prevention and mitigation measures. These strategies include the examination of host resistances, beneficial cultivation practices, sanitation measures, microbiome health maintenance, fungicide choice and resistance, as well as integrated management approaches. This review seeks to enhance our understanding of this globally significant disease, aspiring to assist in the development and improvement of effective prevention and control strategies.

Effects of synthetic and environmentally friendly fungicides on powdery mildew management and the phyllosphere microbiome of cucumber.

Modern agricultural practices rely on synthetic fungicides to control plant disease, but the application of these fungicides has raised concerns regarding human and environmental health for many years. As a substitute, environmentally friendly fungicides have been increasingly introduced as alternatives to synthetic fungicides. However, the impact of these environmentally friendly fungicides on plant microbiomes has received limited attention. In this study, we used amplicon sequencing to compare the bacterial and fungal microbiomes in the leaves of powdery mildew-infected cucumber after the application of two environmentally friendly fungicides (neutralized phosphorous acid (NPA) and sulfur) and one synthetic fungicide (tebuconazole). The phyllosphere α-diversity of both the bacterial and fungal microbiomes showed no significant differences among the three fungicides. For phyllosphere ß-diversity, the bacterial composition exhibited no significant differences among the three fungicides, but fungal composition was altered by the synthetic fungicide tebuconazole. While all three fungicides significantly reduced disease severity and the incidence of powdery mildew, NPA and sulfur had minimal impacts on the phyllosphere fungal microbiome relative to the untreated control. Tebuconazole altered the phyllosphere fungal microbiome by reducing the abundance of fungal OTUs such as Dothideomycetes and Sordariomycetes, which included potentially beneficial endophytic fungi. These results indicated that treatments with the environmentally friendly fungicides NPA and sulfur have fewer impacts on the phyllosphere fungal microbiome while maintaining the same control efficacy as the synthetic fungicide tebuconazole.

First Report of Stem Canker Caused by Diaporthe tulliensis on jasmine in Taiwan.

Diaporthe species can infect forest trees, ornamentals, and crops, causing root and fruit rots, stem cankers, leaf spots, etc. (Yang et al. 2018). In February 2021, about 10-20% of jasmine plants showing stem canker, foot rot, and wilting were observed in Changhua (24°01'57.7"N 120°34'54.7"E), Taiwan. The diseased plants initially showed chlorosis, leaf drop, and dieback. Sunken lesions were observed on the infected stem and kept expanding gradually. Eventually, plants wilted and black spots formed on the lesions. The margin of healthy and infected tissues of six samples were cut into 4 pieces, disinfected with 10% NaOCl for 30 seconds, rinsed twice in sterilized distilled water for 1 minute, and cultured on water agar at 28℃ under 12 h light / 12 h dark cycle. Hyphae grown out from isolated tissues were sub-cultured on potato dextrose agar (PDA). All tissues grown out of fungi showed similar colony morphology. Two hyphal tips from different tissues were isolated as representatives and deposited in Bioresource Collection and Research Center, Hsinchu, Taiwan, under BCRC numbers FU31566 and FU31567. The colonies on PDA were white to pale gray and produced black pycnidial conidiomata. The two-week-old conidiomata scattered or aggregated in small groups, exuded cream to pale yellow conidial droplets, 0.3-1.1 mm (n=50). The α-conidia were one-celled, hyaline, ovoid to cylindrical with one or two droplets, 3.8-6.3 × 2.5-3.8 µm (n=50). ß-conidia were absent. The internal transcribed spacer (ITS), translational elongation factor subunit 1-α (EF1α), and ß-tubulin of the two isolates were amplified using primer pairs ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999), and Bt2a/Bt2b (Glass and Donaldson, 1995), respectively. The ITS (MZ389113, MZ389114), EF1α (MZ419338, MZ419339), and ß-tubulin (MZ408893, MZ408894) sequences of two isolates showed 98.55-98.56% (KR936130), 98.82% (KR936133), and 99.11-99.33% (KR936132) match to those of Diaporthe tulliensis R.G. Shivas, Vawdery & Y.P. Tan ex-type isolate BRIP 62248a (Dissanayake et al. 2017), respectively. Based on the morphological and molecular characters, this fungus is identified as D. tulliensis. To confirm the pathogenicity, the needle-wounded stem bases of eight-month-old cutting jasmine seedlings were inoculated with BCRC FU31566 by two PDA disks with actively grown fungal edges or conidial suspension at the concentration of approximately 2 × 105 conidia/ml. Each method inoculated five seedlings, performed in the greenhouse at 25 ± 2°C. Non-inoculated plants served as control. Two weeks after inoculation, three plants inoculated with PDA disks of the fungal culture showed wilting, and conidiomata formed on the stem base. The same symptoms were observed in one plant inoculated with the conidial suspension 3 weeks after inoculation. By contrast, the controls remained symptomless. Koch's postulates were completed by re-isolating the fungus from the inoculated plant. The re-isolated pathogen showed similar morphology and molecular characteristics to the original. D. tulliensis has been reported to cause cocoa rotted stem in Australia, kiwifruit stem canker in China, and Boston ivy leaf spot in Taiwan (Crous et al. 2015; Bai et al. 2017; Huang et al. 2021; Farr and Rossman 2021). To our knowledge, this is the first report of stem canker on jasmine associated with D. tulliensis in Taiwan. Furthermore, this is the first record of jasmine as a host of D. tulliensis worldwide.

Whole-Genome Sequence Resource of Calonectria ilicicola, the Casual Pathogen of Soybean Red Crown Rot.

Calonectria ilicicola (anamorph: Cylindrocladium parasiticum) is a soilborne plant-pathogenic fungus with a broad host range, and it can cause red crown rot of soybean and Cylindrocladium black rot of peanut, which has become an emerging threat to crop production worldwide. Limited molecular studies have focused on Calonectria ilicicola and one of the possible difficulties is the lack of genomic resources. This study presents the first high quality and near-completed genome of C. ilicicola, using the Oxford Nanopore GridION sequencing platform. A total of 16 contigs were assembled and the genome of C. ilicicola isolate F018 was estimated to have 11 chromosomes. Currently, the C. ilicicola F018 genome represents the most contiguous assembly, which has the lowest contig number and the highest contig N50 among all Calonectria genome resources. Putative protein-coding sequences and secretory proteins were estimated to be 17,308 and 1,930 in the C. ilicicola F018 genome, respectively; and the prediction was close to other plant-pathogenic fungi, such as Fusarium species, within the Nectriaceae family. The availability of this high-quality genome resource is expected to facilitate research on fungal biology and genetics of C. ilicicola and to support advanced understanding of pathogen virulence and disease management.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

First Report of Podosphaera xanthii Causing Powdery Mildew on Zinnia elegans in Taiwan.

Zinnia elegans L., known as common zinnia, is an annual flowering plant belonging to the Asteraceae family and native to North America. The plant has colorful flowers and is one of the popular ornamental bedding plants for gardening. In March 2020, powdery mildew symptoms were observed in a zinnia floral field with an incidence of >70% in Dacun Township, Changhua County, Taiwan. The symptoms were spotted on the stems, flower petals and leaves which appeared as irregular colonies and white patches on the surfaces. When disease progressed, most of the plant surfaces were covered by the white fungal colonies and became yellowish. Under microscopic examination, hyphal appressoria of the fungus were indistinct or slightly nipple-shaped. The conidiophores were unbranched, erect, straight, smooth to slightly rough, 75.0 to 200.0 × 10.0 to 15.0 µm (n=10), composed of a cylindrical, flexuous foot cell, 40.0 to 100.0 × 8.8 to 15.0 µm (n=10), and following 1 to 5 shorter cells. The conidia were ellipsoid to ovoid, 25.0 to 37.5 × 15.0 to 23.8 µm (n=60), with an average length-to-width ratio of 1.8 and contained fibrosin bodies. No chasmothecia were found. Three voucher specimens (TNM Nos. F0033680, F0033681, and F0033682) were deposited in the National Museum of Natural Science, Taichung City, Taiwan. To confirm the identification, the internal transcribed spacer (ITS) regions of the three specimens were amplified using primer pairs ITS1/PM6 and PM5/ITS4 (Shen et al. 2015) and sequenced from both ends. The resulting sequences were deposited in GenBank under Accession Nos. MT568609, MT568610, and MT568611. The sequences were identical to each other and shared a 100% identity with that of Podosphaera xanthii MUMH 338 on Z. elegans from Japan (Accession No. AB040355) (Ito and Takamatsu 2010) over a 475 bp alignment. Accordingly, the fungus was identified as P. xanthii (Castagne) U. Braun & Shishkoff (Braun and Cook 2012) based on its morphological and molecular characters. Pathogenicity was demonstrated through inoculation by gently pressing naturally infected leaves onto leaves of three healthy potted common zinnia that had been sprayed with 0.02% Tween 20. Additional three non-inoculated plants treated in the same way without inoculating the powdery mildew served as the controls. Powdery mildew colonies were observed on inoculated leaves after 10 days at room temperature, later the diseased leaves became yellowish and deteriorated. The morphological traits of the fungus on the inoculated leaves were similar to those of the first observed. In addition, the ITS sequence from a colony on the inoculated leaves was 100% identical to MT568609-MT568611, fulfilling the Koch's postulates. All the controls remained symptomless. Z. elegans is known to be a host for different species of powdery mildew in the genus Erysiphe, Golovinomyces, and Podosphaera (Farr and Rossman 2020). In Taiwan, powdery mildew has been briefly reported on zinnia without detailed descriptions (Hsieh 1983). This study confirmed P. xanthii as a causal agent of powdery mildew in Taiwan and the awareness of the disease may benefit the floral industry. To our knowledge, this is the first confirmed report of P. xanthii on Z. elegans in Taiwan.