Plant Protection
Spartina alterniflora, as an alien invasive plant, has spread rapidly in the Yellow River Delta region, threatened native species, and damaged ecosystem health. This paper analyzes the invasion footprint of Spartina alterniflora in the Yellow River Delta by using remote sensing satellite image analysis techniques. It was found that after Spartina alterniflora completed colonization (before 2004), it quickly occupied the invaded habitat and rapidly spread (2004—2014). Although human intervention had suppressed the invasion speed of Spartina alterniflora and reduced the invasion area in the past decade (2014—2024), it still had the potential to make a comeback and reinvade. Therefore, we further classify and summarize the hypotheses of different stages of Spartina alterniflora invasion, compare various control measures, the prospect of scientific exploration of microbiological control of Spartina alterniflora in the future is proposed. The aim of this study is to provide a new way to prevent and control Spartina alterniflora invasion in the future.
In order to explore the alleviating effect of exogenous ascorbic acid on the toxicity of beet seedlings under atrazine stress and the degradation mechanism of atrazine, using beet 'KWS1197' seeds as experimental materials, pot experiments combined with instrumental analysis were conducted to determine the effects of different concentrations of ascorbic acid on physiological and biochemical indexes of beet under atrazine stress, as well as the pesticide residues and degradation mechanisms in the soil. The results showed that atrazine stress inhibited the growth of beet seedlings, after spraying ascorbic acid, the toxicity of beet seedlings under atrazine stress was alleviated. Spraying 1mmol/L ascorbic acid had the most significant effect. The dry weight of the above-ground part and the underground part was 2.54 times and 3.43 times that of atrazine treatment group (AT treatment group). Chlorophyll content was increased by 42.5%. MDA content and electrolyte permeability were 53.57% and 65.01% of those in AT treatment group. SOD, POD and CAT enzyme activities were reduced by 60.5%, 61.3% and 51.1%, compared with AT treatment group. Spraying ascorbic acid can reduce the residual amount of atrazine in soil, and the higher the concentration, the more obvious the degradation effect. Four degradation products were found, and four possible degradation pathways of atrazine were further speculated. Ascorbic acid can improve the adverse effects of atrazine on the growth of beet seedlings, and the effect is significant at 1 mmol/L. This study provides a reliable reference for the degradation of atrazine.
In order to clarify the effects of rearing with different volume-density combinations on the developmental duration, survival rate, and weight of pupae and adults of the ten-spotted ladybird beetles, under conditions of 25℃, relative humidity of 60% to 80%, and a light cycle of 10 L:14 D, three containers (A: 1000 mL; B: 1500 mL; C: 2000 mL) and 3 densities (15 heads; 20 heads; 25 heads), feeding, recording and analyzing the development period, survival rate, pupal and adult weight of each insect of M. dilatata. The results showed that the survival curve of M. dilatata showed an "S" downward trend with the growth of instar, and the development duration of each treatment was C3>C1>A1=C2>A3>A2=B2>B1>B3, and the average development time of group B was the shortest. The survival rate of the 1st and 2nd instar larval stage and pupal stage of each treatment was lower, and the pupation rate and adult rate of B2 treatment were 76.67% and 73.33%, which were higher than those of the other treatments. The weight of each treatment at pupal stage from high to low was A1>C2>C3>B1>A3>C1>B3>A2>B2, and the weight of adults from high to low was B1>B3>B2>C2>C3>C1>A2>A3>A1. In summary, the best feeding container for M. dilatata should be B2 treatment, that is, 1500 mL feeding density of 20 heads/box is the best. This study provides a theoretical basis for the efficient breeding of larvae of M. dilatata.
In order to clarify the species, biological characteristics, and the control agents of the pathogen of apple scab in Yuexi County, the pathogen was identified and analyzed based on the molecular biology and morphological characteristics, and the biological characteristics of pathogen were studied in different culture medium, pH, carbon source and nitrogen source. The field control effects of 5 common fungicides were studied. The results showed that the pathogen causing apple scab in Yuexi County was identified as Venturia inaequalis. The optimum culture medium was wheat bran agar medium, the optimum pH was 7-8, the optimum carbon source was glucose, and the optimum nitrogen source was peptone. The field control results showed that the five fungicides could effectively control apple scab, and the control effect of 20% pydiflumetofen was the best, with the control effect was 89.54%. The order of the control effect was 20% pydiflumetofen SC> 20% pydiflumetofen·difenoconazole SC> 40% flusilazole EC> 50% kresoxim-methyl WG> 36% thiophanate-methyl SC. The above results showed that 20% pydiflumetofen, 20% pydiflumetofen·difenoconazole and 40% fluosilazole can be applied as reference pesticides for controlling V. inaequalis in field.
Utilizing bibliometric software CiteSpace, a visual exploration was undertaken on 143 relevant publications regarding Arboridia kakogawana in the CNKI database spanning from 1987 to 2024. The analysis encompassed annual publication trends, authorship patterns, institutional affiliations, and prevalent keywords. The objective was to offer insights for future research directions within the A. kakogawana domain. The results indicated that the annual publication of research related to A. kakogawana from 1999 to 2016 was relatively high, with a total of 127 publications and an average of 7 articles per year. There was no widely connected author cooperation network in this field, and most scholars were independent of each other and lack of cooperation and connection. The cooperative relationships among research institutions were not close, presenting an independent distribution status. Over time, the research focus had shifted from the biological characteristics of A. kakogawana to physical control and management. In conclusion, future investigations on A. kakogawana should prioritize interdisciplinary convergence, leverage existing scientific and technological resources, and intensify studies in transcriptomics, predictive habitat suitability assessments, and physicochemical control methodologies.
This study comprehensively reviews the recent research on bacterial degradation of pesticide residues both domestically and internationally, enumerates the common bacteria for degrading pesticide residues in soybeans, conducts an in-depth analysis of the pathways and mechanisms of bacterial degradation of common pesticide residues in soybeans, and deliberates on the impacts of pesticide structure, the intrinsic mechanism of bacteria, and environmental factors on the bacterial degradation of pesticide residues in soybeans. In light of the issues such as soil and crop pollution caused by excessive pesticide use, which adversely affect human health and the ecological environment, the degradation function of bacteria on pesticides can be utilized for improvement, thereby enhancing crop yield and facilitating sustainable agricultural development. It is proposed that the further exploration of bacterial species capable of degrading pesticide residues in soybeans and the strategy of combining bacterial strains in the future should be pursued, with the aim of enhancing soybean yield and quality, reducing the harm of pesticide residues to human health, and providing a reference for ecological protection.
In order to further understand the herbicide resistance of barnyard grass [Echinochloa crus-galli (L.) P. Beauv.] in Jiangsu rice field, the seeds of barnyard grass populations were collected from rice fields in Jiangsu Province from 2019 to 2022, and the resistance of barnyard grass species to metamifop, cyhalofop-butyl, penoxsulam and quinclorac was determined by stem and leaf spray method. The suspected resistant populations of 100 collected barnyard grass populations were screened by differential dose method, and then the resistance index of these suspected resistant populations to the corresponding herbicides was determined by the series concentration of different herbicides. The results showed that there were 10 populations with low resistance, 8 populations with medium resistance and 1 population with high resistance to metamifop; there were 5 populations with low and medium resistance to cyhalofop-butyl; there were 3, 9 and 1 with low, medium and high resistance to penoxsulam, respectively; there were 1, 7 and 1 with low, medium and high resistance to quinclorac, respectively. The tested barnyard grass populations in 13 prefectural level cities in Jiangsu Province, except Changzhou, all have resistant population distribution, and some populations show multiple resistances.
To investigate the antifungal activity of essential oils (EOs) derived from A. tatarinowii and A. argyi, as well as their principal components, we assessed the antifungal efficacy of both EOs against four pathogenic fungi using the Oxford Cup method. Additionally, EO constituents were analyzed through gas chromatography-mass spectrometry (GC-MS). Subsequently, the minimal inhibitory concentration (MIC) and fractional inhibitory concentration index (FICI) were determined through a 96-well plate assay. The results showed that both EOs at a concentration of 50 mg/mL exhibited significant inhibitory effects on Colletotrichum gloeosporioides, followed by Fusarium oxysporum and Fusarium solani. GC-MS analysis revealed that A. tatarinowii EO contained 34 compounds, with β-asarone and α-asarone identified as the primary constituents. In contrast, A. argyi EO comprised 98 compounds, among which caryophyllene, β-caryophyllene, eucalyptol, and myrtenal constituted a substantial proportion. Furthermore, the MIC of β-asarone and α-asarone were found to be comparable to that of hymexazol. When utilized in combination with hymexazol, the two EOs demonstrated an additive impact on Fusarium oxysporum in the pairwise combination experiment. Overall, the EOs and their main components from A. tatarinowii and A. argyi exhibited robust antifungal activity against four fungal pathogens, indicating potential for further research.
The aim of this study was to explore the sensitivity of black soldier fly larvae (Hermetia illucens) to imidacloprid, to understand the impact of pesticide residue on their growth, providing a theoretical basis for the large-scale rearing of black soldier flies. Using bioassay methods, we conducted imidacloprid toxicity tests on 5-day-old and 7-day-old black soldier fly larvae with four treatments of 0.1, 0.5, 1, and 2 mg/kg, and measured mortality rate and larval weight with DMSO and blank controls serving as references. The results showed that for 7-day-old larvae, the mortality rate after 7 days of exposure to concentrations ranging from 0.1 mg/kg to 2 mg/kg was between 3.3% and 17.3%. When the concentration was ≤0.5 mg/kg, imidacloprid significantly promoted the increase in the weight of black soldier flies. Under continuous exposure to feed containing imidacloprid, the treatment at 0.1 mg/kg resulted in a 16.4% increase in individual larval weight compared to the control group. After being switched to regular feed following 3 days of exposure to imidacloprid-containing feed, the individual larval weights in the 0.1 mg/kg and 0.5 mg/kg treatments were 26.2% and 21.4% higher than those in the control group, respectively. Low concentrations of imidacloprid have no obvious adverse effects on the growth of black soldier fly larvae and are able to promote an increase in their body weight, which provides a basis for further research into the stimulatory effects of black soldier flies.
In order to provide reference for rational fertilization and green disease prevention and control in flue-cured tobacco, the effects of boron and silicon nutrient elements on the diseases prevention and control and the physiological mechanism were discussed. The field experiment was conducted to study the effects of different boron and silicon application levels on the incidence of potato virus Y (PVY) disease and defense enzyme activity of flue-cured tobacco named ‘Yunyan 100’. The results showed that the application of boron and silicon reduced the incidence and disease index of PVY in flue-cured tobacco. Compared with the treatment of spraying water (CK), the incidence and disease index of PVY under 9.0 kg/hm2 boron+ 6.0 kg/hm2 silicon treatment decreased by 32.5% and 22%, respectively. Meanwhile, reasonable application of boron and silicon fertilizer significantly improved the defense enzymes activities of tobacco leaves, and the phenylalanine degradation enzyme activity and proline content were significantly increased by 121.4%-426.5% and 30.0%-74.3%, respectively. Correlation analysis showed that the incidence of PVY was significantly negatively correlated with proline content, while phenylalanine degradation enzyme activity was significantly positively correlated with proline content. The combined application of 9.0 kg/hm2 boron+ 6.0 kg/hm2 silicon could reduce the occurrence of diseases and induce the increase of defense enzyme activity.
Sugarcane pokkah boeng disease is a fungal disease caused by multiple species of Fusarium. In order to clarify the pathogen species of sugarcane pokkah boeng disease in Yunnan, thirty-three samples of sugarcane pokkah boeng disease were collected from Kaiyuan and Menglian in Yunnan, and strains FS1 and FS2 were isolated and purified, and their DNA was extracted; the primers of transcription elongation factor (EF-1α), tubulin gene (TUB2), polymerase gene (RPB2) were used for PCR amplification of the isolated strains. The result was that a clear and bright band consistent with the target band was obtained, and the products were sequenced and analyzed by BLAST on the NCBI website, the EF-1α, TUB2 and RPB2 sequences of strains FS1 and FS2 were compared with EF-1α (accession number: MK609907.1), TUB2 (accession number: MT011039.1) and RPB2 (accession number: MW238849.1) of Fusarium sacchari with 100% similarity and coverage. Phylogenetic trees of strains FS1 and FS2 were constructed by maximum likelihood method with MEGA6.0 software, and the results showed that FS1 and FS2 clustered on the same branch with F. sacchari. Therefore, based on the morphological characteristics of strains FS1 and FS2 and the results of molecular biological identification, the pathogen of sugarcane pokkah boeng disease was identified as F. sacchari. F. sacchari spores were inoculated with ‘Yunzhe 08-1609’, and the symptoms of leaf regression and leaf yellowing appeared on the 7th day of inoculation, the infected leaves were isolated and sequenced again. The sequence similarity and coverage between EF-1α of the isolated strain and EF-1α of F. sacchari (accession number: MK609907.1) were 100%. F. sacchari was shown to be the causal agent of sugarcane pokkah boeng disease in Kaiyuan and Menglian.
The cultivation area of Astragalus membranaceus was expanding year by year. However, due to the continuous cropping obstacles, the problems of pests and diseases are becoming more and more serious year by year. In order to provide a basis for the identification and integrated prevention and control of diseases in the planting process of A. membranaceus, this paper reviews the occurrence patterns, pathogen species and prevention and control measures of the main diseases of A. membranaceus. The common diseases of A. membranaceus mainly include root rot, verticillium wilt, powdery mildew, downy mildew, damping-off and leaf spot, etc. Among these diseases, root rot and powdery mildew are particularly harmful to A. membranaceus. For these diseases, traditional prevention and control measures mainly rely on chemical agents, such as carbendazim, thiophanate-methyl and fludioxonil, etc. However, long-term dependence on chemical agents may not only have a negative impact on A. membranaceus itself, but also cause environmental pollution. The use of microorganisms such as Bacillus, Trichoderma and Streptomyces can effectively control the occurrence of diseases, while reducing the impact on the environment. In addition to the above methods, the cultivation of A. membranaceus varieties with strong resistance can fundamentally reduce the occurrence of diseases. Moreover, optimizing cultivation methods and strengthening field management, such as rational crop rotation, improving soil structure, controlling irrigation and fertilization, are also key measures to prevent diseases. In summary, the prevention and control of A. membranaceus diseases should adopt a comprehensive management strategy, including biological control, breeding of disease-resistant varieties, optimization of cultivation techniques and strengthening of field management, so as to achieve efficient and environmentally friendly disease control.
Apple scab caused by Venturia inaequalis Cook (Wint.) is one of the important apple diseases worldwide, which seriously affects the growth, yield, and fruit quality of apple trees. In order to establish a simple, fast, and sensitive molecular detection method for apple scab, a strain of apple scab (V. inaequalis) isolated and identified from the Yili River Valley in Xinjiang was used as the test material. Based on loop-mediated isothermal amplification (LAMP) technology, specific primers were designed and screened using the nucleic acid sequence of the ribosome transcription spacer (ITS) region of the pathogen as the target. A LAMP detection system for apple scab was established, and its specificity and sensitivity were verified. The results showed that among the 10 designed primers, the Venin7 primer could specifically identify apple scab from 4 apple diseases and 1 rust disease, and the detection stability was good; the LAMP detection system had good detection performance for apple scab at amplification temperatures of 55℃-70℃ and within 60-90 minutes; the sensitivity of detecting apple scab was 1 pg/μL, which was more than 103 times higher than that of using specific primers for PCR detection. The LAMP detection technology established in this study can quickly and sensitively detect and monitor apple scab.
To understand the effects of the neonicotinoid insecticide martine on the fertility of peach aphids, this experiment evaluated the effects of martine toxicity and sublethal doses (LC10, LC20, LC30, LC50 and LC70) on adult aphids of Myzus persicae. The results showed that the LC50 of martine against Myzus persicae was 9.66 mg/L, and the LC10, LC20, LC30 and LC70 against Myzus persicae were 0.17, 0.69, 1.86, 50.16 mg/L, respectively. The sublethal concentration of martine can significantly reduce the fertility, longevity, and survival rate of adult Myzus persicae. The life span of adult Myzus persicae in LC10, LC20, LC30, LC50 and LC70 treatment groups was shortened by 0.9, 1.4, 1.9, 3.1 and 4.1 d, respectively. The limiting growth rate (λ), net value-added rate (R0), average generation period (T), total fertility (GRR), and intrinsic growth rate (rm) of Myzus persicae in sublethal concentration treatment groups were lower than those in the control group. It is concluded that the sublethal concentration of martine has a lethal effect on the growth of Myzus persicae population.
To scientifically evaluate the safety of pyraclostrobin on three minor crops (wampee, guava, and pitaya), one-year residual field trials in four sites were conducted on pyraclostrobin 30% suspension concentrate (SC) based on guidelines for field trials of pesticide residues in crop. The dissipation dynamics, final residues, and dietary risk assessment of pyrclostrobin SC on wampee, guava, and pitaya were carried out based on ultra-high performance liquid chromatography tandem triple quadrupole mass spectrometer (UPLC- MS/MS). The sample was extracted with acetonitrile (ACN), purified by PSA, and determined by UPLC- MS/MS. The results showed that when the spiked levels of wampee whole fruit, wampee pulp, guava, pitaya whole fruit and pitaya pulp was from 0.01 to 5.0 mg/kg, the recovery ranged from 104% to 107%, 80% to 96%, 93% to 100%, 83% to 91%, and 90% to 107%, with the relative standard deviation ranging from 0.9% to 3.8%, 2.7% to 5.3%, 3.0% to 10.7%, 1.1% to 4.3%, 2.2% to 6.3%, respectively. The limits of quantification were all 0.01 mg/kg. The initial concentration of pyraclostrobin in wampee, guava, and pitaya was from 2.8 to 4.8, 0.36 to 1.0, 0.48 to 1.40 mg/kg, and the half-lives ranged from 8.8 to 11.4 d, 5.6 to 13.9 d, 3.0 to 3.8 d, respectively, when pyraclostrobin 30% SC was applied at the dosage of 250 mg/kg, thrice. The finial residues in whole wampee and pulp, guava, whole pitaya and pulp was from 0.24 to 2.8, 0.016 to 0.73, 0.20 to 0.46, 0.12 to 3.6, <0.010 to 0.072 mg/kg, when the pre-harvest intervals was 7 and 10 days in wampee and guava, 5 and 7 days in pitaya, respectively. The dietary risk assessment showed there was no unacceptable risk to the health of the general population, when the risk quotient (RQ) of pyraclostrobin was 77.0%. The research results provided support and reference for scientific and rational use of pyraclostrobin 30% SC on three minor crops, and establishing their maximum residue limit (MRL) values.
The study aims to improve the automatic recognition of rice pest and disease images and better guide agricultural pest and disease control. Using a combination of transfer learning and ResNet-18 model, we organized open source plant disease data on the internet, and obtained images of 9 rice pests and diseases, including bacterial blight, blast and Tungro, as well as a healthy leaf as the research objects. 11414 cleaned images were selected to establish a dataset for model training, and the 30% dataset was split as the test set. On the basis of six pre trained models such as ResNet-18, GoogLeNet, VGG-16, and MobileNet-v2, a series of parameter adjustments were made to the transfer model. The results show that: (1) under the consistent training parameters, the proposed model ResNet-18 has significantly higher validation accuracy and lowest loss value compared with MobileNet-v2, AxeNet, VGG-16, GoogLeNet, SqueezeNet, and the original ResNet-18 model. The final accuracy of the model is 96.97%. (2) Compared with the original model, the training accuracy of all transferred learning models has been improved significantly, with the improved accuracy ranging from 5.03% to 13.90%. The optimized training model has the characteristics of fast recognition speed and improved accuracy, which can accurately and quickly identify the type of crop disease, providing support for the automatic diagnosis of crop diseases.
To evaluate the field control effects of several chemical control agents on potato late blight in Matou Town of Tancheng County, Linyi City, Shandong Province, 687.5 g/L fluopyram-penoxifen wettable powder, 72% mancozeb-manganese zinc, 42.8% fluopyram-iprovalent wettable powder, and 10 billion/g Bacillus subtilis biological preparation were selected, and a control group and treatment groups were set up, and the incidence index, control effect, and yield were monitored. The results showed that the 687.5 g/L fluopyram-penoxifen wettable powder had a significant control effect on the disease. In 2020, the incidence index was 3.21, 5.13, and 6.02 after three applications of the treatment, with an average control effect of over 80% and a maximum of 85.14%, and an increase in yield of 27.9%. In 2021, the incidence index was 2.95, 4.75, and 5.45 after three applications of the treatment, with an average control effect of over 84% and an increase in yield of 26.0%. The 42.8% fluopyram-iprovalent wettable powder had a slightly lower control effect but was better than other pesticides. The importance of selecting control agents based on regional specific conditions was emphasized, and fluopyram-penoxifen wettable powder was recommended as the preferred control agent for late blight of potato in the study area. The research results provide scientific control guidelines for farmers.
Isolation and identification of culturable bacteria in the intestinal tract of Holotrichia scrobiculata Brenske adults feeding on Ginkgo biloba leaves provided a theoretical basis for the study of host adaptability mechanism and comprehensive prevention and control of Holotrichia scrobiculata Brenske. The intestinal culturable bacteria of female and male adults of Holotrichia scrobiculata Brenske feeding on Ginkgo biloba leaves were isolated, cultured and identified by LB, NA and TYA medium, combined with 16S rDNA sequence analysis, to explore the species diversity of intestinal culturable bacteria of Holotrichia scrobiculata Brenske feeding on Ginkgo biloba leaves. The composition and structure of culturable bacteria in the intestinal tract of female and male adults were different. There were 4 phyla, 11 families, 13 genera and 14 species of culturable bacteria in the intestinal tract of female adults. The dominant phylum, family, genus and species of bacteria were Firmicutes, Bacillaceae, Bacillus and Bacillus subtilis, with abundances of 86.58%, 86.56%, 62.59% and 61.64%, respectively. There were 3 phyla, 6 families, 7 genera and 11 species of culturable bacteria in the intestinal tract of male adults. The dominant phyla, families, genera and species were Firmicutes, Bacillaceae, Pediococcus and Pediococcuspentosaceus, with abundances of 98.64%, 37.74%, 34.68% and 34.68%, respectively. From the perspective of dominant bacteria, the dominant bacteria in the female intestinal tract were Bacillus subtilis, with an abundance of 61.64%, while the dominant bacteria in the male intestinal tract were Bacillus altitudinis and Pediococcuspentosaceus, with relative abundances of 31.91% and 34.68%, respectively. Pediococcuspentosaceus and Sphingomonas humi were the two common culturable bacteria in the intestines of female and male adults. The diversity of culturable bacterial species in the intestinal tract of Holotrichia scrobiculata Brenske adults feeding on Ginkgo biloba leaves was rich. The composition of intestinal bacterial species varied with the gender of female and male, and the dominant species were also different.
To establish a solid theoretical foundation for the efficient management of insect pests in corn crops, practical plant protection strategies that reduce the amount of pesticides should be explored. A study was conducted to investigate the occurrence of Spodoptera frugiperda on maize in the mountainous area of Mengga Town, Mangshi City, Dehong Prefecture, Yunnan Province. Two types of pesticides, 5% emamectin benzoate and 15% indoxacarb, were tested on Spodoptera frugiperda in corn fields using plant protection drones and knapsack electric sprayers. Spodoptera frugiperda larvae can cause damage in the whole growth period of maize, and the infestation rate, damage index, number of insects per 100 plants, and the proportion of different insect ages in different growth stages of maize are significant different, and Spodoptera frugiperda is the most harmful in the big bell stage of maize. Two different methods of applying 5% emamectin benzoate and 15% indoxacarb had a significant impact on the incidence of Spodoptera frugiperda in maize fields. The damage rate and index of maize also showed a significant decrease between 3 to 14 days after application. There was no significant difference in the relative control efficacy of the same pesticide against Spodoptera frugiperda under two different methods. Still, the use of plant protection drones pesticide application had the advantages of labor-saving, time-saving, and pesticide-saving. Spodoptera frugiperda control had a positive effect on increasing the production of maize in the yield, and the experimental treatments results showed a significant increase in yield of the test variety 'Yunrui 62', with 25.28% to 28.93% production increase compared to the control treatment. In total, it is recommended to use UAVs equipped with anti-spray technology to protect plants during large-scale Spodoptera frugiperda control. Additionally, it's important to conduct thorough investigations and implement field management practices to prevent corn insect infestations, which are crucial for achieving high and stable crop yields. It's important to focus on integrating, demonstrating, and promoting the use of this technology in the future.
To clarify the pathogen causing leaf spot on Begonia semperflorens in Guangdong, samples of begonia leaf spot from Panyu District, Guangzhou in Guangdong were collected as test materials. Strains were isolated by tissue isolation method. The taxonomic status of pathogens was identified based on pathogenicity determination, morphological and molecular biological characteristics. A total of 13 single-conidium-isolates with similar morphological characteristics were obtained from diseased plant samples. Artificial inoculation results showed that the tested isolates could infect Begonia semperflorens and cause typical leaf spot symptoms observed in the field. Their colonies were light gray-green with abundant aerial hyphae on PDA medium. Conidiophores were brown, solitary, (36.4-102.8) μm×(4.6-8.6) μm (n=50). Conidia were brown, obclavate, obpyriform, oval, (25.6-72.5) μm×(15.4-26.3) μm (n=50), with three to seven transverse and zero to three longitudinal septa. Based on a phylogenetic tree obtained using multiplex alignments of concatenations of ITS, TEF-1α, GAPDH, Alt a1 and RPB2 genes sequences from 21 Alternaria species, two tested isolates were grouped together with four Alternaria tomato strains to form a single clade. This study clarified that the pathogen causing begonia leaf spot in Guangdong was determined as A. tomato, which was reported for the first time that A. tomato could cause begonia leaf spot.
Plant Protection
