First report of Colletotrichum karstii causing anthracnose on soybean in China.

Soybean (Glycine max) is a significant grain and oil crop. Among the various challenges faced by soybean cultivation, anthracnose stands out as one of the most prevalent diseases. In June 2023, anthracnose symptoms on leaves characterized by irregular disease spots featuring gray-white centers and brown edges, along with many small black dots on their surface, were observed in a 20-hectare soybean (variety "Liu Yuehuang") field located in Luodian County (25°40'20″ N, 106°53'50″ E, 575 m), Guizhou Province, China. Around 30% of the 300 soybean plants examined were symptomatic, and a total of ten leaves were collected. Fragments (5×5 mm) from the edge of disease spots were sheared and surface-sterilized with 3% sodium hypochlorite and 75% ethanol for 60 s and 30 s, respectively. They were then flushed twice with sterile water, dried using sterile filter papers, finally placed on potato dextrose agar (PDA) and incubated at 28°C for two days. In total, 11 isolates with identical morphological characteristics were obtained. The colonies grown with white aerial mycelia on their surface; conidia were cylindrical, both ends are rounded, aseptate, hyaline, 11.0-14.0 (12.5) × 4.5-6.0 (5.0) µm (n = 30); appressoria were nearly ovoid, brown to black, 8.5-10.5 (9.5) × 5.5-7.5 (6.0) µm (n = 30). The morphological characteristics closely resembled the description of C. karstii (Damm et al., 2012). To further identify the isolates, chitin synthase (CHS-1), actin (ACT), beta-tubulin (TUB2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the internal transcribed spacer (ITS) loci were amplified by using CHS-79F/CHS-345R, ACT-512F/ACT-783R (Carbone and Kohn, 1999), Bt2F/Bt2R (Woudenberg et al., 2009), GDF/GDR (Guerber et al., 2003) and ITS1/ITS4 (White et al., 1990) PCR primers, respectively. The BLAST results showed that the sequences of two representative strains, LD 2023048-1 and LD 2023048-2, were highly similar to those of strain C. karstii CGMCC3.14194 (ITS: OR342620 (99%) and OR342621 (99%) with HM585409, ACT: OR412337 (97%) and OR423341 (100%) with HM581995, CHS-1: OR423344 (99%,) and OR423345 (100%) with HM582023, GAPDH: OR423348 (98%) and OR423349 (98%) with HM585391, and TUB: OR423352 (99%) and OR423353 (99%) with HM585428). The phylogenetic tree combined five sequences showed that the two strains clustered into a branch of C. karstii CGMCC3.14194 with high support values. Thirty-day-old soybean plants (n = 10) (variety Liu Yuehuang) were separately sprayed with 1 × 105 spore suspensions/mL of the two strains by spray method, and plants sprayed with sterile distilled water were used as the negative control (n = 5). All the plants were then covered with plastic bags and cultured in the greenhouse (28℃, 80% humidity, 12 h light dark cycle). After ten days of inoculation, plants inoculated with C. karstii began to produce typical anthracnose symptoms, while the control remained asymptomatic. The confirmation of the reisolated pathogen as C. karstii was established through a comprehensive analysis of morphology and five sequencing loci. Pathogenicity tests were repeated three times. Anthracnose on soybean is caused by Colletotrichum spp. reported in China including C. truncatum (Hu et al., 2015), C. brevisporum (Shi et al., 2021) and C. fructicola (Xu et al., 2023). As far as we know, this study is the initial report of C. karstii inducing anthracnose on soybean to date, which establishes a fundamental reference for preventing and controlling this disease.

Pepper vein yellow virus P0 protein triggers NbHERC3, NbBax, and NbCRR mediated hypersensitive response.

P0 proteins encoded by the pepper vein yellow virus (PeVYV) are pathogenic factors that cause hypersensitive response (HR). However, the host gene expression related to PeVYV P0-induced HR has not been thoroughly studied. Transcriptomic technology was used to investigate the host pathways mediated by the PeVYV P0 protein to explore the molecular mechanisms underlying its function. We found 12,638 differentially expressed genes (DEGs); 6784 and 5854 genes were significantly upregulated and downregulated, respectively. Transcriptomic and reverse-transcription quantitative polymerase chain reaction (RT-qPCR) analyses revealed that salicylic acid (SA) and jasmonic acid (JA) synthesis-related gene expression was upregulated, and ethylene synthesis-related gene expression was downregulated. Ultrahigh performance liquid chromatography-tandem mass spectrometry was used to quantify SA and JA concentrations in Nicotiana benthamiana, and the P0 protein induced SA and JA biosynthesis. We then hypothesized that the pathogenic activity of the P0 protein might be owing to proteins related to host hormones in the SA and JA pathways, modulating host resistance at different times. Viral gene silencing suppression technology was used in N. benthamiana to characterize candidate proteins, and downregulating NbHERC3 (Homologous to E6-AP carboxy-terminus domain and regulator of choromosome condensation-1 dmain protein 3) accelerated cell necrosis in the host. The downregulation of NbCRR reduced cell death, while that of NbBax induced necrosis and curled heart leaves. Our findings indicate that NbHERC3, NbBax, and NbCRR are involved in P0 protein-driven cell necrosis.

First report of Powdery Mildew Caused by Podosphaera xanthii on Siraitia grosvenorii in Guizhou, China.

Swingle (Siraitia grosvenorii), a member of the Cucurbitaceae family, stands out as a distinctive plant with both economic and medicinal significance. In October 2023, severe powdery mildew were observed on S. grosvenorii in Guiyang City (26.50°N; 106.66°E), Guizhou Province, China. About 80 % of the plants in the greenhouse showed powdery mildew symptoms. Three infected plant samples were selected for morphological and molecular analysis (GZAAS 23-0801, GZAAS 23-0802 and GZAAS 23-0803). The voucher specimens are deposited in the Key Laboratory of Agricultural Biotechnology of Guizhou Province. The symptoms initially manifested as irregular to nearly circular, small yellow spots, with distinct depressions as well as surfaces covered in white mycelium. Over time, these spots gradually expanded and merged patches. In the final stages, the entire leaves turned into yellow and withered. Microscopic observations showed that fungal hyphae were septate, branched, and flexuous to straight and 5 to 9 µm wide, and appressoria were indistinct to slightly nipple-shaped. Conidia were hyaline and ellipsoid to oval with fibrosin bodies and measured 31 to 43 × 18 to 24 µm (n = 50) with a length/width ratio of 1.3 to 2.3. Conidiophores were unbranched, straight, 120 to 268 × 14 to 22 µm (n = 30), producing two to five immature conidia in chains. Foot cells of conidiophores were cylindrical, 39 to 84 × 8 to 14 µm (n = 30), followed by one to three short cells. Short cells were cylindrical, 12 to 32 × 8 to 15 µm (n = 50). The morphological characteristics were identical with the previous description of Podosphaera xanthii (Braun and Cook, 2012). Total DNA was extracted from conidia and mycelia by the Chelex method (Walsh et al., 1991). The ribosomal DNA internal transcribed spacer (ITS) and nuclear ribosomal large subunit (LSU) were amplified by using the primers ITS1/ITS4 (White et al., 1990) and LSU1/LSU2 (Scholin et al., 1994), respectively. The ITS (OR825802, OR825803 and OR825804, respectively) and LSU (OR825805, OR825806 and OR825807, respectively) sequences of three isolates, were deposited in GenBank. The BLAST results revealed that both the ITS and LSU region sequence were 100% identical to those of P. xanthii (ITS: MF043939, MG754404 and KJ698669; LSU: OQ061319, AB936277and OP218411). Phylogenetic analyses of ITS and LSU sequences showed that our three isolates were clustered with P. xanthii (KX842351, LC270782 and LC270779) with high statistical support (ML/MP/BI: 100%/97%/1.00). Combined with their morphological characteristics, these three isolates were identified as P. xanthii. Pathogenicity tests were performed by gently brushing conidia onto the leaves of five healthy S. grosvenorii plants. Five non-inoculated plants were used as the control. All plants were maintained in a greenhouse at 25 ± 2°C. One week after inoculation, similar symptoms were observed in the inoculated plants, whereas no symptoms occurred on the control plants. By microscopic observation, the fungus on the inoculated plants was morphologically identical to those on originally diseased plants. Powdery mildew caused by P. xanthii has been reported on Vernonia cinerea (Wu et al., 2023), Vigna unguiculata (Zhang et al., 2023), Cucumis melo (Meesam et al., 2023). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on S. grosvenorii in Guizhou, China. The occurrence of powdery mildew on S. grosvenorii may pose a potential threat to its large-scale cultivation. The pathogen could become a threat to other Cucurbitaceae members in the future.

Tax thresholds yield multiple optimal cooperation levels in the spatial public goods game.

Income redistribution, which involves transferring income from certain individuals to others, plays a crucial role in human societies. Previous research has indicated that tax-based redistribution can promote cooperation by enhancing incentives for cooperators. In such a tax system, all individuals, irrespective of their income levels, contribute to the tax system, and the tax revenue is subsequently redistributed to everyone. In this study, we relax this assumption by introducing a tax threshold, signifying that only individuals with incomes exceeding the threshold will be subject to taxation. In particular, we employ the spatial public goods game to investigate the influence of tax rates-the percentage of income allocated to tax-and tax thresholds, which determine the income level at which individuals become taxable, on the evolution of cooperation. Our extensive numerical simulations disclose that tax thresholds produce complex outcomes for the evolution of cooperation, depending on tax rates. Notably, at low tax rates (i.e., below 0.41), as the tax threshold increases, discontinuous phase transitions in cooperation performance suggest the presence of multiple intervals of effective tax thresholds that promote peak cooperation levels. Nevertheless, irrespective of the chosen tax rate, once the tax threshold surpasses a critical threshold, the redistribution mechanism fails, causing the collapse of cooperation. Evolutionary snapshots show that self-organized redistribution forms an intermediary layer on the peripheries of cooperative clusters, effectively shielding cooperators from potential defectors. Quantitative analyses shed light on how self-organized redistribution narrows the income gap between cooperators and defectors through precise identification of tax-exempt entities, thereby amplifying the cooperative advantage. Collectively, these findings enhance our comprehension of how income redistribution influences cooperation, highlighting the pivotal role of tax thresholds.

Transcriptome Analysis and Functional Identification of Xa13 and Pi-ta Orthologs in Oryza granulata.

Nees & Arn. ex Watt, a perennial wild rice species with a GG genome, preserves many important genes for cultivated rice ( L.) improvement. At present, however, no genetic resource is available for studying . Here, we report 91,562 high-quality transcripts of assembled de novo. Moreover, comparative transcriptome analysis revealed that 1311 single-copy orthologous pairs shared by and (Zoll. & Moritzi) Baill. that may have undergone adaptive evolution. We performed an analysis of the genes potentially involved in plant-pathogen interactions to explore the molecular basis of disease resistance, and isolated the full-length cDNAs of () and () orthologs from . The overexpression of in Nipponbare and functional characterization showed enhanced the resistance of transgenic Nipponbare to rice blast resulting from the presence of the gene. , an alternatively spliced transcript of the blast resistance gene in encodes a 1024-amino acid polypeptide with a C-terminal thioredoxin domain. This study provides an important resource for functional and evolutionary studies of the genus .

De novo genome assembly of Oryza granulata reveals rapid genome expansion and adaptive evolution.

The wild relatives of rice have adapted to different ecological environments and constitute a useful reservoir of agronomic traits for genetic improvement. Here we present the ~777 Mb de novo assembled genome sequence of Oryza granulata. Recent bursts of long-terminal repeat retrotransposons, especially RIRE2, led to a rapid twofold increase in genome size after O. granulata speciation. Universal centromeric tandem repeats are absent within its centromeres, while gypsy-type LTRs constitute the main centromere-specific repetitive elements. A total of 40,116 protein-coding genes were predicted in O. granulata, which is close to that of Oryza sativa. Both the copy number and function of genes involved in photosynthesis and energy production have undergone positive selection during the evolution of O. granulata, which might have facilitated its adaptation to the low light habitats. Together, our findings reveal the rapid genome expansion, distinctive centromere organization, and adaptive evolution of O. granulata.