Fusarium wilt is one of the most important diseases of Eleocharis dulcis (Chinese water chestnut) in China. In order to characterize the pathogens responsible, 69 Fusarium isolates were collected from diseased plants in E. dulcis production areas of the Chinese provinces Anhui, Fujian, Hubei, Hunan, Jiangsu, and Zhejiang. These were then identified based on morphological and molecular characteristics. F. commune was the most common species (92.8%) and was widely distributed in the six provinces. A novel species within the Gibberella fujikuroi species complex (GFSC) was found in Hubei and Zhejiang provinces (5.8%), and an unidentified Fusarium sp. was found only in Hubei province (1.4%). Thirty F. commune isolates from different provinces and four GFSC isolates were selected for sequence analyses of the translation elongation factor 1-α (EF-1α), the mitochondrial small subunit (mtSSU) ribosomal DNA, and the nuclear ribosomal intergenic spacer region (IGS). Maximum parsimony and Bayesian analyses of the multilocus sequence data of these two species plus other taxa showed that the two species formed two distinct, well-supported clades among the three individual and combined gene genealogies. Isolates from different locations were scattered, with no evidence of geographic specialization. Pathogenicity assays showed that the two Fusarium spp., including the unidentified Fusarium sp., were pathogenic to E. dulcis ‘Tuanfeng seven’. There was no relationship between the source of isolates and their pathogenicity. This is the first description of F. commune, a novel species within the GFSC, and an unidentified Fusarium sp. as causal agents of Fusarium wilt of E. dulcis in China.

Mulberry (Morus alba L.) has been grown worldwide as a crop for silkworm rearing for over five thousand years (Jiao et al. 2020). In July 2021, a leaf spot disease was observed on mulberry leaves i...

Mulberry (Morus alba L.) has been cultivated for thousands of years in many temperate regions in East Asia and is commonly used to feed silkworms. In May 2021, 5 to 8% incidence of stem blight on 4-year-old mulberry 'Nongsang 14' was observed in several orchards in Nanzhang County, Hubei Province, China. The roots and stems showed symptoms of vascular discoloration, and the tender new shoots, surrounded by white hyphae, were detached easily. Symptomatic stem tissues (5 mm × 5 mm) were excised from the border between diseased and healthy tissues, surface sterilized in a 75% ethanol solution for 30 s and 2.5% sodium hypochlorite for 1.5 min, washed three times in sterile distilled water, then placed on potato dextrose agar (PDA, 250 g potatoes, 2% dextrose, 1.6% agar), and incubated at 25°C in darkness. Two isolates (Bq2 and Bq3) were subcultured using the single-spore method. On PDA, colonies were cottony, with whitish aerial mycelium and the daily growth rate was 4.25 to 5.50 mm/day at 25°C in darkness. On carnation leaf agar, macroconidia were fusiform with slightly curved apical cells and foot-shaped basal cells, three to five septate, measuring 47.5 to 80.3 × 3.6 to 5.6 μm (average 68.7 × 4.7 μm, n = 30). On spezieller nährstoffarmer agar, microconidia were produced in false heads on monophialides, mostly 0-septate, oval, obovoid, or reniform in shape, measuring 5.1 to 10.7 × 2.7 to 5.3 μm (average 8.5 × 3.3 μm, n = 30). Chlamydospores were 4.9 to 11.0 μm in diameter (average 6.8 μm, n = 30), round shaped, thick-walled, and produced individually or in pairs or in chains. For molecular identification, the ribosomal internal transcribed spacers (ITS), translation elongation factor 1α (EF-1α), 28S large subunit nrDNA (LSU), and calmodulin (CAM) genes were amplified and sequenced with primers ITS1/ITS4 (White et al. 1990), EF1H/EF2T (O'Donnell et al. 1998), LR0R/LR5 ( Vilgalys and Hester 1990; Vilgalys and Sun 1994), and CL1/CL2A (Geiser et al. 2021; Wang et al. 2011), respectively. The sequences were deposited in GenBank (OQ711943-OQ711944 for ITS, OQ722438- Q722439 for EF-1α, OQ722441-OQ722442 for CAM, and OR116152-OR116153 for LSU). A maximum-likelihood phylogenetic analysis based on multilocus sequences was conducted using MEGA7, which showed that the two isolates grouped into a clade with Neocosmospora mori (previously Fusarium solani species complex) supported by a high bootstrap value (85%), and hence, they were identified as N. mori based on morphological and molecular analyses (Brooks et al. 2022; Crous et al. 2021; Lombard et al. 2015; Zeng and Zhuang 2023). To complete Koch's postulates, three healthy 2-month-old seedlings grown in sterile peat mix were removed from pots and the roots were washed in sterile water. Each plant was inoculated by dipping wounded and unwounded roots in a spore suspension (1 × 10⁷ conidia/ml) for 20 min, and then 10 mL of the spore suspension was poured over the roots of each seedling after transplanting. Three plants were treated with sterilized water as a control. The tested plants were then kept in a plastic box containing sterile water and incubated at 25°C in a 12 h/12 h light/dark cycle. The pathogenicity assay was repeated three times for each isolate. Root and stem blight was observed 10 days after inoculation, while the control plants were asymptomatic. Furthermore, fungi with morphological characteristics of N. mori were only reisolated from the symptomatic stems and sequences of LSU matched those of isolates Bq2 and Bq3. This pathogen has been reported previously causing stem blight on mulberry trees in Japan and South Korea (Sandoval-Denis et al. 2019), but to our knowledge, this is the first report of N. mori causing root rot and stem blight of mulberry in China. This report will facilitate the development of effective control strategies for the disease.

Mulberry fruit sclerotiniose is a prevalent disease caused by the fungal species Ciboria shiraiana, C. carunculoides, and Scleromitrula shiraiana of the order Helotiales, and severely affects the production of mulberry. However, these species have only been identified using morphological and rDNA-ITS sequence analyses, and their genetic variation is unclear. To address this, morphological and two-locus (ITS and RPB2) phylogenetic analyses were conducted using culture-dependent and independent methods for 49 samples from 31 orchards across four provinces in China. Illumina MiSeq sequencing was used to assess the fungal communities obtained from fruits varying in disease severity and color from an orchard in Wuhan. Conidial suspensions of C. shiraiana and C. carunculoides isolated from diseased fruits, diseased fruits affected with hypertrophy and pellet sorosis sclerotiniose, and mycelia of Sclerotinia sclerotiorum were determined to be pathogenic to the mulberry cultivar YSD10. However, fruits inoculated with S. sclerotiorum mycelia exhibited nontypical disease symptoms, and mycelia and conidia obtained from C. carunculoides and S. shiraiana strains were not pathogenic. Maximum parsimony and Bayesian analyses using the sequences of the assessed loci indicated species variability with no evidence of geographic specialization. Metagenomic analysis revealed that the diversity of fungal communities was reduced with disease progression. Furthermore, within a single fruit, the presence of two Ciboria spp. was detected. These results provide novel insights into Ciboria spp., revealing the secondary infections caused by conidia in diseased fruits, genetic variations of the pathogens, and the occurrence of coinfection. This improved understanding of fungal pathogens will aid in developing effective disease control strategies.

The excessively concentrated ripening period of mulberries causes seasonal surplus. Fruit mulberry (Morus spp.) exhibits the unique trait of “simultaneous flowering and leaf flushing”, rendering budburst timing closely correlated with fruit ripening time. Thus, deciphering the molecular mechanism underlying winter bud dormancy maintenance in fruit mulberry is urgently needed. Herein, an F₁ hybrid population comprising 337 individuals, derived from Morus wittiorum (♀) and ‘322’ (♂), was utilized as research material. Through Bulked Segregant Analysis Sequencing (BSA-Seq), we successfully mapped a dormancy-associated QTL interval designated as LB (Late Burst), spanning 9,990,001–11,990,000 bp on Chromosome 13. Integrating Weighted Gene Co-expression Network Analysis (WGCNA) results, MaSVP was identified as a candidate gene within this interval. Virus-induced gene silencing (VIGS) of MaSVP in winter buds of Morus wittiorum significantly accelerated budburst compared to the control, demonstrating that MaSVP represses winter bud dormancy release and plays a crucial role in regulating dormancy maintenance in fruit mulberry. Dynamic expression profiling of dormancy-related genes revealed that the transcript levels of MaSVP, MaSAPK3, MaCASL2, and MaPYR8 were significantly downregulated (Tukey’s test, p < 0.05) as budburst approached, whereas those of MaFT and MaGA20ox1-D were significantly upregulated (Tukey’s test, p < 0.05). These results indicate that winter bud dormancy maintenance in Morus wittiorum is associated with abscisic acid (ABA) and gibberellin (GA) metabolism. Collectively, this study provides critical insights into the biological basis of winter bud dormancy maintenance in fruit mulberry and offers valuable genetic resources for breeding late-maturing cultivars.