Introduction
Buffalobur (Solanum rostratum Dunal), a member of the Solanum genus in the Solanaceae family, is a ubiquitous well-known invasive weed that has led to reduced biodiversity and disrupted the ecological balance of invaded ecosystems (Zhou et al. Reference Zhou, Cao, Zhang, Jin, Wang, Ma, Chen and Cui2023). Originating as a native North American weed, S. rostratum has now spread to 21 countries and regions across Europe, Oceania, South America, Africa, and Asia (Yan et al. Reference Yan, Wang and Zheng2022). In China, it was first found in Chaoyang County, Liaoning Province, in 1981 (Guan et al. Reference Guan, Gao, Li, Ye, Xin and Li1984). In the last four decades, its invasion has been reported in nine provinces, including cities and autonomous regions such as Liaoning, Beijing, Jilin, Hebei, Shanxi, Xinjiang, Inner Mongolia, Tianjin, and Ningxia. The weed continues to spread, affecting the growth of native grasses and crops, as well as human and animal activities, resulting in considerable ecological damage and economic losses (Sun et al. Reference Sun, Liu, Tang, Tang, Cong, Lu, Liu and Feng2023).
To control the spread of S. rostratum, researchers have primarily focused on artificial mechanical removal, chemical control (Abu-Nassar and Matzrafi Reference Abu-Nassar and Matzrafi2021; Zhang et al. Reference Zhang, Zhao, Wang, Fu, Hu, Zhao, Hou, Xu and Li2017), and planting alternative plants (Institute of Agricultural Environment and Sustainable Development 2019). These methods could effectively control S. rostratum. However, due to its high fertility and strong adaptability to different environments, complete eradication remains challenging (Zhao et al. Reference Zhao, Solis-Montero, Lou and Vallejo-Marín2013). Biological control presents remarkable advantages in terms of green environmental protection and sustainable efficacy. This approach exhibits the potential to induce mortality in affected plants, offering promising prospects in the field of weed management (Hewitt et al. Reference Hewitt, Galea and O’Donnell2024). Despite these advantages, biological control for S. rostratum is not widely reported, particularly within the context of natural pathogens, with a notable lack of research on pathogenic microorganisms. Only a few studies have examined S. rostratum infection with Potato spindle tuber virus (Singh and Bagnall Reference Singh and Bagnall1968), Tomato golden mottle virus (Mauricio-Castillo et al. Reference Mauricio-Castillo, Arguello-Astorga, Ambriz-Granados, Alpuche-Solís and Monreal-Vargas2007), and Alternaria alternata (Guo et al. Reference Guo, Han, Zhang, Lu, Wang, Wang, Baldwin, Li, Li and Shao2019) in S. rostratum, which caused disease. Therefore, exploring and using pathogenic microbial resources targeting S. rostratum is of immense significance. Fungal pathogens represent a promising potential microbial resource for biological control due to their high species diversity, specificity, strong sporulation ability, and potential for large-scale production (Yan et al. Reference Yan, Wang and Zheng2022).
In this study, S. rostratum leaves showing typical symptoms, such as discoloration, necrosis, rot, wilting, and deformation, were collected from Liaoning and Jilin provinces in China. The fungal pathogens were isolated and purified, and their species were identified based on morphological and molecular biological characteristics. The pathogenicities of fungi for the seeds, isolated leaves, and plants of S. rostratum were tested, and the safety of fungi for eight other plant species was also evaluated. To the best of our knowledge, this is the first study in China on the fungal pathogens of S. rostratum, including Epicoccum sorghinum, Fusarium equiseti, Curvularia hawaiiensis, and Nigrospora oryzae. Our findings provide a reference for subsequent screening of potential biocontrol fungi and enriching the resources for biological control of S. rostratum.
Materials and Methods
Survey Location
A comprehensive investigation was performed across eight locations in Liaoning Province and Jilin Province, including Shuangta District, Longcheng District, Chaoyang County, Beipiao, and Karaqin Left Mongolian Autonomous County in Liaoning Province, and Songyuan Taobei District, and Da’an in Jilin Province. In Liaoning Province, S. rostratum was predominantly found along the Daling River basin, inhabiting riverbanks and roadsides, whereas in Jilin Province, S. rostratum was primarily distributed in grasslands, wastelands, and roadsides (Table 1).
Table 1. Overview of survey sites.
Investigation and Collection of Fungal Pathogens
Plants infected with pathogenic fungus were collected. Photos were taken to document the diseased sections of the plants, and the severity of the disease was noted. Disease severity was categorized into six levels based on the percentage of the leaf affected: grade 0: no leaves; grade 1: 1% to 5%; grade 2: 5% to 25%; grade 3: 25% to 50%; grade 4: 50% to 75%; and grade 5: 75% to 100% (including dead plants) (Ray and Hill Reference Ray and Hill2012; Zhu and Qiang Reference Zhu and Qiang2004).
Isolation and Purification of Fungal Pathogens
Pathogens were isolated according to the method described by Fang (Reference Fang1998). Approximately 5 by 5 mm fragments of symptomatic tissues were excised from the edges of lesions. These tissue fragments were then surface sterilized by immersion in 75% ethanol for 30 s and 1% NaClO for 2 min; subsequently washed three times with sterile distilled water; then placed onto potato dextrose agar (PDA) plates, with five pieces per plate; and incubated at 28 C in the dark for 7 d in the climatic cabinet (ZRG, Ningbo 67 Jiangnan-1500A-L). All growing colonies were sorted, and mycelia from the edge of each colony were selected onto PDA medium; pure cultured isolates were obtained by continuous transfer. The successfully isolated and purified strains were maintained on a PDA slope and stored at 4 C.
Identification of the Fungal Pathogens
The morphology of the colonies was observed and noted. Spores were collected to prepare a spore suspension, and 5 μl of this suspension was inoculated on clean, dry slides to prepare temporary slides. The morphological characteristics of the conidia and conidial stalks were observed under an optical microscope (40×, McAudi, Stellar 1 Pro).
Fresh fungus (75 mg) was completely ground into powder in liquid nitrogen. Pathogenic fungal DNA of pathogenic was extracted using the UNIQ-10 Bio-Tex DNA kit (Sangon Biotech, No. 698, Xiangmin Road, Songjiang District, 123 Shanghai, China) according to the manufacturer’s instructions. The extracted pathogen DNA was amplified by polymerase chain reaction (PCR) using an internal transcribed spacer (ITS1/ ITS4) (Gardes and Bruns Reference Gardes and Bruns1993). PCR was performed using a final volume of 25 μl containing 12.5 μl Taq PCR Master Mix, 1 μl of each primer, 2 μl of DNA, and 8.5 μl of ddH2O. The amplification conditions for the ITS region were as follows: initial denaturation at 94 C, followed by denaturation at 94 C for 30 s, annealing at 51 C for 30 s, extension at 72 C for 45 s, with 30 cycles, a final extension step of 10 min at 72 C, and preservation at 4 C. Finally, the PCR products were analyzed using 1% agarose gel electrophoresis, and the PCR products with obvious bands were sent to Sangon Biotech for sequencing. The multilocus sequences were compared with the sequences previously deposited in the GenBank database using the BLAST tool. A phylogenetic tree was constructed with the neighbor-joining method using MEGA v. 7.0 software (Mega Limited, Auckland, New Zealand) with 1,000 bootstrap replications to clarify the taxonomic status of fungi.
Pathogenicity Test
Determination of Germination Inhibition by Fungal Pathogens
To prepare fungal spore suspensions, the concentration of conidia was adjusted to 1 × 106 spores ml−1. On a superclean bench (Lichen, SW-CJ-1D), two layers of sterilized filter paper were placed into a sterile culture dish (diameter = 90 mm). Subsequently, 5 ml of the prepared spore suspension was added to the dish, and 20 seeds of S. rostratum were placed in each dish. The dishes were incubated at 28 C in darkness with 75% humidity. The control group was treated with an equal amount of sterile water instead of the spore suspension, and each treatment was replicated three times. Germination was considered to have occurred when the radicle appeared. More suspension was added as necessary during the experiment to maintain moisture. The germination status of the seeds was observed, and the length of the radicle was measured every day after germination to determine the radicle germination length inhibition rate.
Pathogenicity of Fungal Pathogens on Isolated Leaves
Solanum rostratum leaves of uniform shape and size were subjected to disinfection by immersion in 75% alcohol for 30 s, with 3% NaClO solution for 1 min, and washed with sterile water three times. Three leaves were horizontally scratched using a sterilized insect needle at a distance of 2 mm from the main vein. Six wounds of 2 mm each were made, with the aim of penetrating the lower epidermis while keeping the upper epidermis intact. A 7-d fungal disk (diameter = 5 mm) was taken from the PDA medium, and the mycelia-bearing side was placed on the leaf surface and tightly adhered to the wound site. Agar plugs (5 mm) from the PDA were used as the negative control, and each treatment was repeated three times. The treated leaves were placed in a culture dish lined with a layer of sterile filter paper at the bottom, moistened with sterile water, and incubated at 28 C with 90% humidity. After 48 h, the fungal disks were removed. The disease symptoms on each leaf were observed and recorded, and the shapes and areas of the lesions were observed. The pathogen was re-isolated using the tissue isolation method. It was considered the same if its morphological characterization and molecular characterization were consistent with the original inoculated strain.
Pathogenicity of Fungal Pathogens on Solanum rostratum
When the plant grew four true leaves, the leaves were rinsed three times with 75% alcohol and 3% NaClO solution and then three times with sterile water. Each leaf was horizontally scratched using a sterilized insect needle at a distance of 2 mm from the main vein to make six wounds of 2 mm each. Then, 10 μl of spore suspension was sprayed onto the leaves to inoculate them, with an equal amount of sterile water used as the negative control, and each treatment was repeated three times. After inoculation, the plants were bagged in fresh bags for 48 h and incubated at 28 C with 90% humidity.
Safety Evaluation of Fungal Pathogens for Test Plants
When the test plants grew four true leaves, the leaves were sprayed with 10 μl of spore suspension. The negative control was sprayed with an equal amount of sterile water Each treatment was repeated three times. Culture conditions and determination methods were the same as those for the pathogenicity test. After 3 d, the disease symptoms of each plant were investigated.
Statistical Analysis
Data analysis was performed with one-way ANOVA followed by Duncan’s multiple-range test (P ≤ 0.05) using SPSS v. 26.0 software (IBM, New York, America).
The inhibition rate of radicle length was calculated as (Wang et al. Reference Wang, Zhang, Sun, Xu and Dong2010):
The incidence was calculated as:
The percentage of the leaf disease area in the total leaf area was graded as follows: grade 0: no disease; grade 1: 1% to 5%; grade 2: 5% to 25%; grade 3: 25% to 50%; grade 4: 50% to 75%; grade 5: 75% to 100% (including dead plants) (Ray and Hill Reference Ray and Hill2012; Zhu and Qiang Reference Zhu and Qiang2004).
The disease index was calculated as (Chaube and Singh Reference Chaube and Singh1991):
Pathogenicity was determined as: disease index is 0, not pathogenic; disease index is 0 to 25, weakly pathogenic; disease index is 25 to 50, medium pathogenic; disease index is 50 to 100, strongly pathogenic (Hebei Administration for Market Regulation 2021).
Safety was determined as: disease index is 0 to 5, no symptoms, NS; disease index is 5 to 10, slightly susceptible, LS; disease index is 10 to 50, moderately susceptible, MS; disease index is 50 to 100, severely susceptible, SS (Cheng et al. Reference Cheng, Cheng, Zhu, Li, Wei and Guo2023; Li et al. Reference Li, Cheng, Zhu and Guo2014).
Results and Discussion
Occurrence of Solanum rostratum Disease
Solanum rostratum has fewer diseases in the seedling stage and more diseases in the adult and flowering stages, mainly in leaves. In the early stage of the disease, spots were observed on the leaves. In the later stage, the area of the spots expanded into patches, with some leaves yellowing and withered, and the plant grew poorly. Five typical diseased leaves were collected (Figure 1), and the specific symptoms are described in Table 2. Guo et al. (Reference Guo, Han, Zhang, Lu, Wang, Wang, Baldwin, Li, Li and Shao2019) reported the emergence of yellowish to black spots on the diseased leaf surfaces of S. rostratum in Xinjiang, China, which is different from what was observed in our study.
Figure 1. Disease symptoms of Solanum rostratum as outlined in Table 2: (A) symptom 1, (B) symptom 2, (C) symptom 3, (D) symptom 4, (E) and symptom 5.
Table 2. Typical symptoms and habitat of Solanum rostratum.
Identification of Fungal Pathogens
Morphological Identification
Pathogens were isolated from 120 diseased leaves collected from various survey sites, and 16 distinct fungal strains were obtained. Following cultivation and observation, these strains were classified into five species based on their cultural characteristics and colony morphology on PDA plates (Figure 2). Detailed descriptions of the colony and spore morphologies are shown in Table 3. Based on the colony and spore morphological characteristics, five fungi were identified as Alternaria sp., Epicoccum sp., Fusarium sp., Curvularia sp., and Nigrospora sp.
Figure 2. Colony and conidial morphological characteristics of Solanum rostratum pathogens. (A-1 and A-2) Colony morphology of BP-2; (A-3) conidial morphology of BP-2; (B-1 and B-2) colony morphology of BP-3; (B-3) conidial morphology of BP-3; (C-1 and C-2) colony morphology of JL-1; (C-3) conidial morphology of JL-1, (D-1 and D-2) colony morphology of JL-3; (D-3) conidial morphology of JL-3; (E-1 and E-2) colony morphology of JL-4; (E-3) conidial morphology of JL-4.
Table 3. Pathogen identification characteristics of Solanum rostratum and morphological identification results.
Molecular Identification
Molecular identification was performed along with morphological identification. The ITS-PCR results determined that the ITS fragment lengths of fungal pathogens BP-2, BP-3, JL-1, JL-3, and JL-4 were 574 bp, 541 bp, 544 bp, 533 bp, and 499 bp, respectively (Figure 3). Homology alignment was performed with known sequences in the BLAST database. The highest homology was found with A. alternata, E. sorghinum, F. equiseti, C. hawaiiensis, and N. oryzae, at 99%, 100%, 100%, 100%, and 99%, respectively, and the corresponding accession numbers in GenBank were OR342085, OR342086, OR342087, OR272046, and OR342088.
Figure 3. PCR amplification electrophoregram of Solanum rostratum pathogens.
These five fungi are common plant pathogens. Alternaria alternata can infect various invasive weeds such as croftonweed [Ageratina adenophora (Spreng.) R.M. King & H. Rob.] and water hyacinth [Eichhornia crassipes (Mart.) Solms] (Dai et al. Reference Dai, Chen, Qiang, An and Zhang2004; Yirefu et al. Reference Yirefu, Struik, Lantinga and Tessema2017). Both E. sorghinum and F. equiseti exhibit herbicidal activity on the alfalfa (Medicago sativa L.) and native weed large crabgrass [Digitaria sanguinalis (L. ) Scop.] (Jiang et al. Reference Jiang, Xu, Han, Karen, Ji, Li and Zhao2021; Kang et al. Reference Kang, Zhang, Wan, Xu, Li and Cao2019). These pathogens can also cause leaf spot and stem rot in various crops such as corn (Zea mays L.), rice (Oryza sativa L.), and cabbage (Brassica oleracea L.) (Aslam et al. Reference Aslam, Gleason, Ikram, Alam, Ahmed, Mansha, Yasin, Hameed and Amrao2019; Yang et al. Reference Yang, Wang, Zhang, Lin, Xu and Liu2022).
Inhibition of Solanum rostratum Seed Germination by Fungal Pathogens
The germination rate of seeds in both control and pathogen challenge conditions was 100%. However, the germination length of the seed radicle was suppressed after the challenge with all five pathogens, and N. oryzae led to the strongest inhibition. The average germination lengths after treatment with N. oryzae for 24 h and 48 h were significantly lower than those of the control group and other treatments, with lengths of 1.00 mm and 1.04 mm, respectively (F = 4.35, df = 5, 114, P < 0.05). After 72 h, the average germination length of all seeds challenged with pathogens was significantly lower than that of the control group, with N. oryzae exhibiting the shortest germination length of 1.54 mm (F = 8.69, df = 5, 114, P < 0.05) and the highest inhibition rate of 47.76% on radicle germination of the seeds (Table 4).
Table 4. Germination length and inhibition rate of seed radicle after treatment with five pathogens. a
a The data in the table are the mean ± SD; different letters within the same column indicate significant differences (P < 0.05, Duncan’s new multiple-range test).
Pathogenicity of Fungal Pathogens on Isolated Leaves of Solanum rostratum
Following the inoculation of five pathogenic fungal disks onto isolated leaves of S. rostratum, noticeable disease spots were observed after 3 d. The disease spots started to spread across the inoculation area. By 7 d, the diseased area had spread significantly. Leaves at the inoculation site exhibited signs of damage, and the color of the diseased spots transitioned from gray to a mix of gray and black. After 11 d, the leaves had turned yellow and gradually withered following inoculation with A. alternata, E. sorghinum, and N. oryzae (Figure 4). The pathogens were subsequently isolated from the inoculated leaves for identification, and it was confirmed that they were identical to the pathogens used in the inoculation, verifying Koch’s rule.
Figure 4. Leaf disease symptoms after inoculation with mycelia. (A-1, A-2, and A-3) Leaf disease symptoms after inoculation with Alternaria alternata at 3 d, 7 d, and 11 d. (B-1, B-2, and B-3) Leaf disease symptoms after inoculation with Epicoccum sorghinum at 3 d, 7 d, and 11 d. (C-1, C-2, and C-3) Leaf disease symptoms after inoculation with Fusarium equiseti at 3 d, 7 d, and 11 d. (D-1, D-2, and D-3) Leaf disease symptoms after inoculation with Curvularia hawaiiensis at 3 d, 7 d, and 11 d., (E-1, E-2, and E-3) Leaf disease symptoms after inoculation with Nigrospora oryzae at 3 d, 7 d, and 11 d.
Pathogenicity varied among the different fungi. The incidence rate after inoculation was 100% for A. alternata, F. equiseti, and N. oryzae, followed by E. sorghinum and C. hawaiiensis, with incidence rates of 92.46% and 88.10%, respectively. After inoculation with N. oryzae for 3 d and 7 d, the percentage of the diseased leaf area inoculated was significantly higher compared with the other four pathogens, measuring 32.6% (F = 26.23, df = 5, 12, P < 0.05) and 37.66% (F = 8.21, df = 5, 12, P < 0.05). After 11 d, the percentage of the diseased leaf area reached its highest level at 40.87%, with a disease index of 60, indicating that N. oryzae exhibits strong pathogenicity. Alternaria alternata followed, with the percentage of diseased leaf area being 28.33% after 11 d and a disease index of 46.67, demonstrating moderate pathogenicity (Table 5).
Table 5. Pathogenicity analysis of mycelia on isolated leaves of Solanum rostratum a
a The data in the table are the mean ± SD; different letters within the same column indicate significant differences (P < 0.05, Duncan’s new multiple-range test).
Pathogenicity of Fungal Pathogens on Solanum rostratum
Following the inoculation of five fungal spore suspensions on plants of S. rostratum, typical disease spots started to appear on the leaves (Figure 5). Small disease spots were observed on the leaves after 3 d of inoculation. By 7 d, these disease spots had expanded, and necrosis was observed in the tissue surrounding the inoculated leaves. At 11 d, the leaves inoculated with E. sorghinum and N. oryzae exhibited damage and curling, with yellowing edges. The pathogens were subsequently isolated from the inoculated leaves for identification and were found to be identical to the pathogen used in the inoculation, verifying Koch’s rule.
Figure 5. Leaf disease symptoms after inoculation with spore suspension. (A-1, A-2, and A-3) Leaf disease symptoms after inoculation with Alternaria alternata at 3 d, 7 d, and 11 d. (B-1, B-2, and B-3) Leaf disease symptoms after inoculation with Epicoccum sorghinum at 3 d, 7 d, and 11 d. (C-1, C-2, and C-3) Leaf disease symptoms after inoculation with Fusarium equiseti at 3 d, 7 d, and 11 d. (D-1, D-2, and D-3) Leaf disease symptoms after inoculation with Curvularia hawaiiensis at 3 d, 7 d, and 11 d. (E-1, E-2, and E-3) Leaf disease symptoms after inoculation with Nigrospora oryzae at 3 d, 7 d, and 11 d.
Inoculating of five pathogens, the incidence rate was 100% except for C. hawaiiensis. Following inoculation with E. sorghinum and N. oryzae for 3 d and 7 d, the percentages of leaf disease area were highest. After 11 d, the percentage of leaf disease area in seedlings inoculated with E. sorghinum was 67.92%, and the highest disease index was 78.30, followed by N. oryzae with a percentage of 54.17% and a disease index of 70.00, both indicating strong pathogenicity (Table 6).
Table 6. Pathogenicity analysis of mycelia on isolated leaves of Solanum rostratum a
a The data in the table are the mean ± SD; different letters within the same column indicate significant differences (P < 0.05, Duncan’s new multiple-range test).
In this study, all five fungal pathogens exhibited pathogenicity toward S. rostratum, with N. oryzae exhibiting the strongest pathogenicity. Nigrospora oryzae exhibited the highest inhibitory rate on the germination length of the radicle of S. rostratum and showed strong pathogenicity toward isolated leaves and plants. Therefore, N. oryzae was considered the dominant pathogenic fungus for S. rostratum.
Biological control is an important strategy in weed management, effectively supplementing herbicide-based weed control technology (Norsworthy et al. Reference Norsworthy, Ward, Shaw, Llewellyn, Nichols, Webster, Bradley, Frisvold, Powles, Burgos, Witt and Barrett2012). Plant pathogens are an important resource for the development of biological herbicides, exhibiting broad application prospects (Westwood et al. Reference Westwood, Charudattan, Duke, Fennimore, Marrone, Slaughter, Swanton and Zollinger2018). Alternaria sp., Fusarium sp., and Curvularia sp. have been used as biological herbicides (Bendejacq et al. Reference Bendejacq, Gibot, Guillemin, Mouille and Steinberg2024; Chen and Qiang Reference Chen and Qiang2015). The mycelia and toxins of A. alternata, which exhibit rapid infection and strong pathogenicity, have been effectively used against croftonweed (Chen et al. Reference Chen, Reto and Qiang2014; Qiang et al. Reference Qiang, Wang, Wei, Zhou, Chen, Zhu, Dong and An2010). The spores of Fusarium orobanches have been formulated into a biocontrol agent to control the weed Egyptian broomrape (Orobanche aegyptiaca Pers.) in vegetable fields, achieving a prevention rate of greater than 95% (Wang et al. Reference Wang, Zhu and Ma1985). The secondary metabolites produced by Curvularia eragrostidis can significantly inhibit the growth of D. sanguinalis, Chinese sprangletop [Leptochloa chinensis (L.) Nees], and barnyard grass [Echinochloa crus-galli (L.) P. Beauv.] (Jiang and Qiang Reference Jiang and Qiang2005; Julia and Alan Reference Julia and Alan2021). Nigrospora oryzae can be used as a biological control against S. rostratum. Subsequent research can be performed on its fungal toxins, fermentation ability, and formulation processing techniques to increase its pathogenicity (Boyette et al. Reference Boyette, Hoagland and Stetina2019; Duke et al. Reference Duke, Pan, Bajsa-Hirschel and Boyette2022).
Safety of Fungal Pathogens for Tested Plants
After treatments with the five fungal pathogens, the disease indices of all eight other plants tested ranged from 0 to 50. The safety levels were as follows: safe with no symptoms, slightly susceptible, and moderately susceptible with no severe susceptibility (Table 7). The disease indices of N. oryzae on corn, grain sorghum [Sorghum bicolor (L.) Moench], rice, and tomato (Solanum lycopersicum L.) were between 5 and 10, revealing a relatively high level of safety. Furthermore, the disease indices for eggplant (Solanum melongena L.), Tall fescue (Festuca arundinacea Schreb.), smooth bromegrass (Bromus inermis Leyss.), and alfalfa were 0, suggesting that N. oryzae was safe for forage grasses and can be used in grassland habitats. Nigrospora oryzae can infect crops such as corn, sorghum, wheat (Triticum aestivum L.), and cotton (Gossypium hirsutum L.) (Blaszkowski Reference Blaszkowski1994a, Reference Blaszkowski1994b). However, our findings showed that infection with N. oryzae had less effect on the growth of these plants. Because wheat, rice, cotton, and tomato are not cultivated in the concentrated growth areas of S. rostratum in Liaoning Province, this pathogen does not pose a threat to them. For areas surrounding the cultivation of corn and sorghum, physical barriers or isolation measures can be used (Li et al. Reference Li, Cheng, Zhu and Guo2014) during subsequent applications to inhibit the spread of the fungi.
Table 7. Safety evaluation of pathogens for plants a
a NS, no symptoms; LS, slightly susceptible; MS, moderately susceptible; SS, severely susceptible.
The important criteria for candidate strains of biological herbicides include strong pathogenicity, high safety, and ease of industrial production (Chen and Qiang Reference Chen and Qiang2015; Watson Reference Watson1989). In this study, we found that N. oryzae exhibited strong pathogenicity toward S. rostratum and high safety toward tested plants, indicating its potential as a fungal herbicide against S. rostratum.
In the future, the biocontrol potential and application prospects of N. oryzae should be comprehensively evaluated. Additionally, advances in fermentation technology for the pathogen and formulation processing should be prioritized. Furthermore, intensive research into fungal toxins is necessary to enhance their control efficacy and stability, thereby facilitating the development and production of microbial herbicides for S. rostratum. This endeavor would ultimately contribute to reducing the reliance on chemical pesticides, mitigating environmental pollution, and safeguarding human health.
Acknowledgments
The authors are grateful to Yubin Liu, Dongxing Wang (Beipiao Bureau of Agriculture and Rural Affairs, Chaoyang, China), Kunpeng Xi (Agricultural Environmental Protection and Rural Energy Management Station of Baicheng, Baicheng, China), Amanula Yimingniyazi, Bei Xin (Xinjiang Agricultural University, Urumqi, China), Weidong Fu (Institute of Environment and Sustainable Development in Agriculture, Beijing, China), and Mingchao Liu (Shenyang Agricultural University, Shenyang, China) for assistance in the investigation and sample collection.
Funding statement
This work was supported by the National Key R & D Program of China (2021YFD1400300).
Competing interests
The authors declare no conflicts of interest.
