Plant hypersensitive induced reaction protein facilitates cell death induced by secreted xylanase associated with the pathogenicity of Sclerotinia sclerotiorum.

Necrotrophic fungal plant pathogens employ cell death-inducing proteins (CDIPs) to facilitate infection. However, the specific CDIPs and their mechanisms in pathogenic processes of Sclerotinia sclerotiorum, a necrotrophic pathogen that causes disease in many economically important crop species, have not yet been clearly defined. This study found that S. sclerotiorum secretes SsXyl2, a glycosyl hydrolase family 11 xylanase, at the late stage of hyphal infection. SsXyl2 targets the apoplast of host plants to induce cell death independent of xylanase activity. Targeted disruption of SsXyl2 leads to serious impairment of virulence, which can be recovered by a catalytically impaired SsXyl2 variant, thus supporting the critical role of cell death-inducing activity of SsXyl2 in establishing successful colonization of S. sclerotiorum. Remarkably, infection by S. sclerotiorum induces the accumulation of Nicotiana benthamiana hypersensitive-induced reaction protein 2 (NbHIR2). NbHIR2 interacts with SsXyl2 at the plasma membrane and promotes its localization to the cell membrane and cell death-inducing activity. Furthermore, gene-edited mutants of NbHIR2 displayed increased resistance to the wild-type strain of S. sclerotiorum, but not to the SsXyl2-deletion strain. Hence, SsXyl2 acts as a CDIP that manipulates host cell physiology by interacting with hypersensitive induced reaction protein to facilitate colonization by S. sclerotiorum. These findings provide valuable insights into the pathogenic mechanisms of CDIPs in necrotrophic pathogens and lead to a more promising approach for breeding resistant crops against S. sclerotiorum.

CRISPR-targeted mutagenesis of mitogen-activated protein kinase phosphatase 1 improves both immunity and yield in wheat.

Plants have evolved a sophisticated immunity system for specific detection of pathogens and rapid induction of measured defences. Over- or constitutive activation of defences would negatively affect plant growth and development. Hence, the plant immune system is under tight positive and negative regulation. MAP kinase phosphatase1 (MKP1) has been identified as a negative regulator of plant immunity in model plant Arabidopsis. However, the molecular mechanisms by which MKP1 regulates immune signalling in wheat (Triticum aestivum) are poorly understood. In this study, we investigated the role of TaMKP1 in wheat defence against two devastating fungal pathogens and determined its subcellular localization. We demonstrated that knock-down of TaMKP1 by CRISPR/Cas9 in wheat resulted in enhanced resistance to rust caused by Puccinia striiformis f. sp. tritici (Pst) and powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt), indicating that TaMKP1 negatively regulates disease resistance in wheat. Unexpectedly, while Tamkp1 mutant plants showed increased resistance to the two tested fungal pathogens they also had higher yield compared with wild-type control plants without infection. Our results suggested that TaMKP1 interacts directly with dephosphorylated and activated TaMPK3/4/6, and TaMPK4 interacts directly with TaPAL. Taken together, we demonstrated TaMKP1 exert negative modulating roles in the activation of TaMPK3/4/6, which are required for MAPK-mediated defence signalling. This facilitates our understanding of the important roles of MAP kinase phosphatases and MAPK cascades in plant immunity and production, and provides germplasm resources for breeding for high resistance and high yield.

Deciphering the key factors affecting pesticide residue risk in vegetable ecosystem.

Soil contamination, particularly from pesticide residues, presents a significant challenge to the sustainable development of agricultural ecosystems. Identifying the key factors influencing soil pesticide residue risk and implementing effective measures to mitigate their risks at the source are essential. Here, we collected soil samples and conducted a comprehensive survey among local farmers in the Three Gorges Reserve Area, a major agricultural production region in Southwest China. Subsequently, employing a dual analytical approach combining structural equation modeling (SEM) and random forest modeling (RFM), we examined the effects of various factors on pesticide residue accumulation in vegetable ecosystems. Our SEM analysis revealed that soil characteristics (path coefficient 0.85) and cultivation factor (path coefficient 0.84) had the most significant effect on pesticide residue risk, while the farmer factors indirectly influenced pesticide residues by impacting both cultivation factors and soil characteristics. Further exploration using RFM identified the three most influential factors contributing to pesticide residue risk as cation exchange capacity (CEC) (account for 18.84%), cultivation area (account for 14.12%), and clay content (account for 13.01%). Based on these findings, we carried out experimental trials utilizing Integrated Pest Management (IPM) technology, resulting in a significant reduction in soil pesticide residues and notable improvements in crop yields. Therefore, it is recommended that governmental efforts should prioritize enhanced training for vegetable farmers, promotion of eco-friendly plant protection methods, and regulation of agricultural environments to ensure sustainable development.

Binding Mode and Molecular Mechanism of the Two-Component Histidine Kinase Bos1 of Botrytis cinerea to Fludioxonil and Iprodione.

Gray mold caused by Botrytis cinerea is among the 10 most serious fungal diseases worldwide. Fludioxonil is widely used to prevent and control gray mold due to its low toxicity and high efficiency; however, resistance caused by long-term use has become increasingly prominent. Therefore, exploring the resistance mechanism of fungicides provides a theoretical basis for delaying the occurrence of diseases and controlling gray mold. In this study, fludioxonil-resistant strains were obtained through indoor drug domestication, and the mutation sites were determined by sequencing. Strains obtained by site-directed mutagenesis were subjected to biological analysis, and the binding modes of fludioxonil and iprodione to Botrytis cinerea Bos1 BcBos1 were predicted by molecular docking. The results showed that F127S, I365S/N, F127S + I365N, and I376M mutations on the Bos1 protein led to a decrease in the binding energy between the drug and BcBos1. The A1259T mutation did not lead to a decrease in the binding energy, which was not the cause of drug resistance. The biological fitness of the fludioxonil- and point mutation-resistant strains decreased, and their growth rate, sporulation rate, and pathogenicity decreased significantly. The glycerol content of the sensitive strains was significantly lower than that of the resistant strains and increased significantly after treatment with 0.1 µg/ml of fludioxonil, whereas that of the resistant strains decreased. The osmotic sensitivity of the resistant strains was significantly lower than that of the sensitive strains. Positive cross-resistance was observed between fludioxonil and iprodione. These results will help to understand the resistance mechanism of fludioxonil in Botrytis cinerea more deeply.

Amino acid mutation of succinate dehydrogenase complex induced resistance to benzovindiflupyr in Magnaporthe oryzae.

Magnaporthe oryzae is a rice blast pathogen that seriously threatens rice yield. Benzovindiflupyr is a succinate dehydrogenase inhibitor (SDHI) fungicide that effectively controls many crop diseases. Benzovindiflupyr has a strong inhibitory effect on M. oryzae; however, control of rice blast by benzovindiflupyr and risk of resistance to benzovindiflupyr are not well studied in this pathogen. In this study, six benzovindiflupyr-resistant strains were obtained by domestication induced in the laboratory. The MoSdhBH245D mutation was the cause of M. oryzae resistance to benzovindiflupyr, which was verified through succinate dehydrogenase (SDH) activity assays, molecular docking, and site-specific mutations. Survival fitness analysis showed no significant difference between the benzovindiflupyr-resistant and parent strains. Positive cross-resistance to benzovindiflupyr and other SDHIs and negative cross-resistance to azoxystrobin were observed. Therefore, the risk of benzovindiflupyr resistance in M. oryzae might be medium to high. It should be combined with other classes of fungicides (tebuconazole and azoxystrobin) to slow the development of resistance.

Heat Resistance, Virulence, and Gene Expression of Desiccation-Adapted Salmonella Enteritidis During Long-Term Storage in Low-Water Activity Foods.

Desiccation stress could induce crossprotection and even affect virulence of Salmonella enterica. However, the influence of food matrices with low-water activity on desiccation adaptation of Salmonella still remains unclear. This study investigated the survival and adaptation of Salmonella Enteritidis in skim milk powder, ginger powder, and chocolate powder under desiccation storage conditions for a total of 12 weeks. High survival rates of Salmonella Enteritidis in all food matrices maintained over the long-term desiccation storage. Desiccation-adapted Salmonella Enteritidis enhanced heat resistance (p < 0.05) with the increase of storage time. Food composition plays an important role in the induction of crossresistance of desiccation-adapted Salmonella. After desiccation storage, Salmonella Enteritidis in ginger powder was most tolerant to heat treatment. Salmonella Enteritidis in skim milk powder was most resistant to the gastrointestinal simulation environment, and had strongest adhesion to Caco-2 cells. The effects of food composition on gene expression (rpoS, proV, otsA, otsB, grpE, dnaK, rpoH, and sigDE) in desiccation-adapted Salmonella Enteritidis were not significant (p > 0.05). At initial desiccation storage, osmotic protection-related genes (fadA, proV, otsA, and otsB), stress response regulator (rpoS), and heat-resistance-related genes (grpE, dnaK, and rpoH) were all significantly upregulated (p < 0.05). However, after 4-week storage, the expression level of desiccation-related genes, proV, otsA, otsB, grpE, dnaK, and rpoH, significantly decreased (p < 0.05). This study enables a better understanding of Salmonella's responses to long-term desiccation stress in different kinds of low-water activity foods.

Induction of Salmonella Enteritidis into a Viable but Nonculturable State by Cinnamaldehyde and Its Resuscitation.

Trans-cinnamaldehyde (TC), a typical plant-derived compound, has been widely used in the control of foodborne pathogen contamination. Nevertheless, the risk associated with the occurrence of viable but nonculturable (VBNC) bacteria induced by TC remains unclear. The results of this study showed that Salmonella Enteritidis (S. Enteritidis) entered the VBNC state after being induced by TC at a minimum inhibitory concentration of 312.5 µg/mL and survived for at least 22 days under TC treatment. Enhanced resistance was found against heat treatment (75°C, 30 s), antibiotics (i.e., ampicillin, ceftriaxone sodium, chloramphenicol), and hydrogen peroxide (3%) in VBNC S. Enteritidis. A synergistic effect against VBNC S. Enteritidis occurred when TC was combined with acid treatment, including lactic acid and acetic acid (pH = 3.5). VBNC and resuscitated S. Enteritidis by sodium pyruvate treatment (100 mM) were found to retain the infectious ability to Caco-2 cells. Relative expression levels of the stress-related genes relA, spoT, ppx, lon, katG, sodA, dnaK, and grpE were upregulated in VBNC S. Enteritidis. Accumulation of reactive oxygen species (ROS) and protein aggregates was observed in VBNC cells. Besides, the resuscitation of VBNC cells was accompanied with clearance of ROS and protein aggregates. In summary, this study presents a comprehensive characterization of stress tolerance and resuscitation of VBNC S. Enteritidis induced by cinnamaldehyde, and the results provide useful information for the development of effective control strategy against VBNC pathogenic bacteria in food production.

Changes in mass allocation play a more prominent role than morphology in resource acquisition of the rhizomatous Leymus chinensis under drought stress.

BACKGROUND AND AIMS: Plants can respond to drought by changing their relative investments in the biomass and morphology of each organ. The aims of this study were to quantify the relative contribution of changes in morphology vs. allocation and determine how they affect each other. These results should help us understand the mechanisms that plants use to respond to drought events. METHODS: In a glasshouse experiment, we applied a drought treatment (well-watered vs. drought) at early and late stages of plant growth, leading to four treatment combinations (well-watered in both early and late periods, WW; drought in the early period and well-watered in the late period, DW; well-watered in the early period and drought in the late period, WD; drought in both early and late periods, DD). We used the variance partitioning method to compare the contribution of organ (leaf and root) biomass allocation and morphology to the leaf area ratio, root length ratio and root area ratio, for the rhizomatous grass Leymus chinensis (Trin.) Tzvelev. KEY RESULTS: Compared with the continuously well-watered treatment, the leaf area ratio, root length ratio and root area ratio showed increasing trends under various drought treatments. The contribution of leaf mass allocation to leaf area ratio differed among the drought treatments and was 2.1- to 5.3-fold greater than leaf morphology, and the contribution of root mass allocation to root length ratio was ~2-fold greater than that of root morphology. In contrast, root morphology contributed more to the root area ratio than biomass allocation under drought in both the early and late periods. There was a negative correlation between the ratio of leaf mass fraction to root mass fraction and the ratio of specific leaf area to specific root length (or specific root area). CONCLUSIONS: This study suggested that organ biomass allocation drove a larger proportion of variation than morphological traits for the absorption of resources in this rhizomatous grass. These findings should help us understand the adaptive mechanisms of plants when they are confronted with drought stress.

Genetic Diversity and Pathogenic Variation of the Rice False Smut Pathogen Ustilaginoidea virens from Different Rice Cultivars.

Rice false smut, caused by Ustilaginoidea virens, has become one of the most devastating grain diseases of rice worldwide. Understanding the genetic diversity of U. virens is essential for efficient disease control and breeding for disease resistance. However, little is known about the genetic variation of U. virens from different rice cultivars. We investigated the genetic diversity and pathogenic variation of U. virens isolates from 10 rice cultivars in Zhejiang, China. A total of 260 polymorphic loci and 27 haplotypes were identified based on the 2,137-bp combined DNA fragments of all individuals; hap_4 was the most common haplotype, represented by 41 isolates. Phylogeny indicated that all isolates were divided into four genetic groups. Group I was the largest, with 98 isolates, distributed mainly in eight cultivar populations, whereas 90% of the isolates collected from a Changxiang cultivar were clustered in Group IV. Furthermore, the pairwise FST values exhibited significant genetic differentiation in 27 of the pairwise comparisons between populations, accounting for 23.21% of the total genetic variation. The genetic composition of the isolates of the CX population was distinguishable from that of the other nine populations, and genetic recombination was found in a few isolates. Finally, 27 haplotype representative isolates showed high variation in pathogenicity, and the isolates from the genetic subpopulation I were likely to be more virulent than those from genetic subpopulations II and III. Collectively, these findings suggest that differences in rice cultivars play an important role in the genetic variation of U. virens.

Regio- and Enantioselective Synthesis of Dihydropyrido[1,2-a]indoles via Catalytic Asymmetric Annulative Allylic Alkylation.

A palladium-catalyzed asymmetric annulative allylic alkylation reaction of 2-[(1H-indol-2-yl)methyl]malonates with (E)-but-2-ene-1,4-diyl dicarbonates is described, leading to the regio- and enantioselective synthesis of dihydropyrido[1,2-a]indoles with a chiral cyclic allyl stereocenter adjacent to the ring-junction nitrogen atom in moderate to good yields. The salient features of this protocol include mild conditions, a broad substrate scope, and good compatibility with substituents as well as high regio- and stereoselectivities, providing a catalytic asymmetric entry for fabricating chiral pyridoindole scaffolds.

Rapid Identification of a Stripe Rust Resistance Gene YrXK in Chinese Wheat Line Xike01015 Using Specific Locus Amplified Fragment (SLAF) Sequencing.

Wheat stripe rust, an airborne fungal disease caused by Puccinia striiformis Westend. f. sp. tritici, is one of the most devastating diseases of wheat. Chinese wheat cultivar Xike01015 displays high levels of all-stage resistance (ASR) to the current predominant P. striiformis f. sp. tritici race CYR33. In this study, a single dominant gene, designated YrXk, was identified in Xike01015 conferring resistance to CYR33 with genetic analysis of F2 and BC1 populations from a cross of Mingxian169 (susceptible) and Xike01015. The specific length amplified fragment sequencing (SLAF-seq) strategy was used to construct a linkage map in the F2 population. Quantitative trait loci (QTL) analysis mapped YrXk to a 12.4-Mb segment on chromosome1 BS, explaining >86.96% of the phenotypic variance. Gene annotation in the QTL region identified three differential expressed candidate genes, TraesCS1B02G168600.1, TraesCS1B02G170200.1, and TraesCS1B02G172400.1. The qRT-PCR results showed that TraesCS1B02G172400.1 and TraesCS1B02G168600.1 are upregulated and that TraesCS1B02G170200.1 is slightly downregulated after inoculation with CYR33 in the seedling stage, which indicates that these genes may function in wheat resistance to stripe rust. The results of this study can be used in wheat breeding for improving resistance to stripe rust.

Characterization of Genetic Diversity and Variation in Pathogenicity of the Rice False Smut Pathogen Ustilaginoidea virens from a Single Source.

Rice false smut, caused by Ustilaginoidea virens, is one of the most destructive fungal diseases in rice-growing countries. Studies of the genetic diversity, evolution, and pathogenicity of U. virens can provide more information for disease control and cultivar breeding. Contrary to previous studies on the genetic diversity of different geographical populations of U. virens, this study analyzed the genetic variation of U. virens from different panicles of the same rice cultivar in a field in Yunnan Province using single nucleotide polymorphism molecular markers. A total of 183 polymorphic loci and five haplotypes, hap_1 to hap_5, were identified based on the 1,350-bp combined DNA fragment of 127 isolates, showing some genetic diversity. Hap_1 and hap_3 had the highest occurrence, indicating they were the dominant haplotypes in the field. Further analysis showed that most rice panicles could be coinfected by different haplotypes, and even a few spikelets could be coinfected by multiple haplotypes. The phylogeny indicated that all isolates were divided into five genetic groups. Groups I, II, and III clustered together and were distinguished from Groups IV and V. Significant genetic variations in five pairwise comparisons of panicle populations, accounting for 72.45% of the total variation, were found according to FST values. This variation might be caused by different field microenvironments and the uneven distribution of inoculum sources. An unweighted pair-group method with arithmetic means dendrogram and the population structure revealed that the genetic composition of the isolates collected from YN1, YN2, and YN4, which were dominated by the same genetic subgroup, was different from that collected from YN3. Finally, genetic recombination was found in 11 isolates; hap_2 and hap_5, probably as genetic recombination progenies produced by sexual hybridization between hap_1 and hap_3, acquired a greater virulence than their ancestors according to population structure and pathogenicity analyses. These results will help us understand the genetic diversity, evolution, and infection process of U. virens and aid in the development of more effective management strategies for rice false smut, including new cultivars with improved resistance.

Genetic Diversity and Population Structure of the Rice False Smut Pathogen Ustilaginoidea virens in the Sichuan-Chongqing Region.

Rice false smut caused by Ustilaginoidea virens is one of the most devastating fungal diseases of rice panicles worldwide. In this study, two novel molecular markers derived from single nucleotide polymorphism-rich genomic DNA fragments and a previously reported molecular marker were used for analyzing the genetic diversity and population structure of 167 U. virens isolates collected from nine areas in the Sichuan-Chongqing region, China. A total of 62 haplotypes were identified, and a few haplotypes with high frequency were found and distributed in two to three areas, suggesting gene flow among different geographical populations. All isolates were divided into six genetic groups. Groups I and VI were the largest, with 61 and 48 isolates, respectively. The pairwise FST values showed significant genetic differentiation among all compared geographical populations. Analysis of molecular variance showed that intergroup genetic variation accounted for 40.17% of the total genetic variation, while 59.83% of genetic variation came from intragroup genetic variation. The unweighted pair-group method with arithmetic means dendrogram and population structure revealed that the genetic composition of isolates collected from Santai, Nanchong, Yongchuan, and Wansheng dominated by the same genetic subgroup was different from those collected from other areas. In addition, genetic recombination was found in a few isolates. These findings will help to improve the strategies for rice false smut management and resistance breeding, such as evaluating breeding lines with different isolates or haplotypes at different elevations and landforms.

Moderately prolonged dry intervals between precipitation events promote production in Leymus chinensis in a semi-arid grassland of Northeast China.

BACKGROUND: Climate change is predicted to lead to changes in the amount and distribution of precipitation during the growing seasonal. This "repackaging" of rainfall could be particularly important for grassland productivity. Here, we designed a two-factor full factorial experiment (three levels of precipitation amount and six levels of dry intervals) to investigate the effect of precipitation patterns on biomass production in Leymus chinensis (Trin.) Tzvel. (a dominant species in the Eastern Eurasian Steppe). RESULTS: Our results showed that increased amounts of rainfall with prolonged dry intervals promoted biomass production in L. chinensis by increasing soil moisture, except for the longest dry interval (21 days). However, prolonged dry intervals with increased amount of precipitation per event decreased the available soil nitrogen content, especially the soil NO3--N content. For small with more frequent rainfall events pattern, L. chinensis biomass decreased due to smaller plant size (plant height) and fewer ramets. Under large quantities of rain falling during a few events, the reduction in biomass was not only affected by decreasing plant individual size and lower ramet number but also by withering of aboveground parts, which resulted from both lower soil water content and lower NO3--N content. CONCLUSION: Our study suggests that prolonged dry intervals between rainfall combined with large precipitation events will dramatically change grassland productivity in the future. For certain combinations of prolonged dry intervals and increased amounts of intervening rainfall, semi-arid grassland productivity may improve. However, this rainfall pattern may accelerate the loss of available soil nitrogen. Under extremely prolonged dry intervals, the periods between precipitation events exceeded the soil moisture recharge interval, the available soil moisture became fully depleted, and plant growth ceased. This implies that changes in the seasonal distribution of rainfall due to climate change could have a major impact on grassland productivity.

SsCat2 encodes a catalase that is critical for the antioxidant response, QoI fungicide sensitivity, and pathogenicity of Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum is a destructive necrotrophic fungal pathogen with worldwide distribution. The metabolism of reactive oxygen species (ROS) is critical for the development and infection process of this economically important pathogen. Hydrogen peroxide (H2O2) is converted into water and dioxygen by catalases, which are major ROS scavengers in cells. Several genes have been predicted to encode the catalases of S. sclerotiorum, but the critical ones that function in the ROS stress response are still unknown. In this research, a catalase gene called SsCat2 was found to contribute to the predominant catalase activity at the stages of hyphae growth and sclerotial development. SsCat2 transcripts were induced under oxidative stress, and the target deletion of SsCat2 led to significant sensitivity to H2O2, suggesting that SsCat2 is critical in dealing with the oxidative stress. SsCat2-deletion strains were sensitive to hyperosmotic stresses and cell membrane-perturbing agents, suggesting impairment in cell integrity due to the inactivation of SsCat2. The expression of the alternative oxidase-encoding gene was upregulated in the SsCat2-deletion strains, which showed decreased sensitivity to QoI fungicides. SsCat2-deletion strains showed impaired virulence in different hosts, and more H2O2 accumulation was detected during the infect processes. In summary, these results indicate that SsCat2 encodes a catalase that is related to the oxidative stress response, QoI fungicide sensitivity, and pathogenicity of S. sclerotiorum.

In Silico Identification of the Full Complement of Subtilase-Encoding Genes and Characterization of the Role of TaSBT1.7 in Resistance Against Stripe Rust in Wheat.

Plant subtilases (SBTs) or subtilisin-like proteases comprise a very diverse family of serine peptidases that participates in a broad spectrum of biological functions. Despite increasing evidence for roles of SBTs in plant immunity in recent years, little is known about wheat (Triticum aestivum) SBTs (TaSBTs). Here, we identified 255 TaSBT genes from bread wheat using the latest version 2.0 of the reference genome sequence. The SBT family can be grouped into five clades, from TaSBT1 to TaSBT5, based on a phylogenetic tree constructed with deduced protein sequences. In silico protein-domain analysis revealed the existence of considerable sequence diversification of the TaSBT family which, together with the local clustered gene distribution, suggests that TaSBT genes have undergone extensive functional diversification. Among those TaSBT genes whose expression was altered by biotic factors, TaSBT1.7 was found to be induced in wheat leaves by chitin and flg22 elicitors, as well as six examined pathogens, implying a role for TaSBT1.7 in plant defense. Transient overexpression of TaSBT1.7 in Nicotiana benthamiana leaves resulted in necrotic cell death. Moreover, knocking down TaSBT1.7 in wheat using barley stripe mosaic virus-induced gene silencing compromised the hypersensitive response and resistance against Puccinia striiformis f. sp. tritici, the causal agent of wheat stripe rust. Taken together, this study defined the full complement of wheat SBT genes and provided evidence for a positive role of one particular member, TaSBT1.7, in the incompatible interaction between wheat and a stripe rust pathogen.

Rapid Quantification of Fungicide Effectiveness on Inhibiting Wheat Stripe Rust Pathogen (Puccinia striiformis f. sp. tritici).

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important and devastating diseases of wheat; therefore, it is necessary to rapidly and accurately quantify fungicide effectiveness to monitor Pst sensitivity and manage the disease. In this study, a rapid method of quantifying the fungicide effectiveness with detached leaves was developed. The results showed that 0.5% water agar containing 75 µg/ml of 6-benzylaminopurine and filter paper worked the best for maintaining wheat leaves. The disease incidences of different concentrations of spore suspension were compared. When the spore concentrations were 5 and 10 mg/ml, the disease incidences had no significant differences at 12 and 15 days after inoculation (P < 0.05). Fungicide treatment tests revealed that there were no significant differences in the efficacies of triadimefon on rust suppression between detached leaves in the culture dishes and direct spray on seedlings. We also developed a Photoshop software method that can replace the current classification method and accurately measure the proportion of sporulation area on infected leaves. The sensitivity baseline of Pst to triadimefon was estimated as 0.1453 ± 0.0081 µg/ml, and all the values of EC50 were tested for normal distribution using the Shapiro-Wilk test (W = 0.204). The baseline can be used to test the sensitivity of different Pst isolates to triadimefon.

Population Structure and Aggressiveness of Sclerotinia sclerotiorum From Rapeseed (Brassica napus) in Chongqing City.

Sclerotinia sclerotiorum is one of the most devastating fungal plant pathogens of oilseed Brassica and is distributed worldwide. In particular, Sclerotinia stem rot has always been a serious threat to rapeseed production in Chongqing City, China. In this study, simple sequence repeat (SSR) markers and mycelial compatibility groups (MCGs) were used to characterize the population structure of 90 geographic isolates of S. sclerotiorum collected from rapeseed in nine counties of Chongqing. A total of 52 microsatellite haplotypes were identified, and a few haplotypes were found with high frequency. Gene diversity ranged from 0.1570 to 0.4700 in nine populations. A constructed unweighted pair group with arithmetic mean dendrogram based on Nei genetic distance and a STRUCTURE analysis revealed that the genetic composition of the isolates collected in the five counties located in western Chongqing are different from those collected in the two eastern counties, suggesting that breed lines should be cultivated in both the western and eastern regions to effectively evaluate resistance levels. A total of 47 MCGs were identified, and 72% of the MCGs was represented by single isolates. Seven of 13 MCGs that included at least two isolates contained isolates from only one county. SSR haplotypes were not correlated with MCGs. A subset of 34 isolates were inoculated on rapeseed stems, and the aggressiveness showed variation. This research revealed the population genetic structure and aggressiveness of this pathogen in Chongqing, and the results will help to develop disease management and resistance screening strategies.

Antimicrobial Activities of Tea Polyphenol on Phytopathogens: A Review.

The use of natural antimicrobial compounds in crop production has gained much attention from consumers and the agricultural industry. Consequently, interest in more natural, non-synthetic antimicrobials as potential alternatives to conventional chemical pesticides to combat phytopathogens has heightened. Tea polyphenol (TP), a unique and highly important functional component of tea plants, has been reported to possess antimicrobial properties against a wide spectrum of plant pathogens. The aim of this review is to discuss the emerging findings on the mechanisms of antimicrobial action, and the antimicrobial properties of TP, including their major components, effectiveness, and synergistic effects. More studies, particularly field studies, are still necessary to establish conclusive evidence for the effectiveness of TP against phytopathogens. However, the basic conclusion from existing studies suggests that TP is a potential antimicrobial agent for pesticide reduction in agricultural systems.