Variations of phyllosphere microorganisms in asymptomatic and tobacco brown spot leaves before and after spraying 12% difenoconazole + fluxapyroxad SC

12%difenoconazole+fluxapyroxad SC(commercial name:Jiangong)was first released by BASF in China in 2016.It has been registered to control many diseases,including pear scab,apple Alternaria leaf spot,tomato early blight,cucumber powdery mildew,etc.This study evaluated the bioactivity of Jiangong against Alternaria alternata and explored variations of phyllosphere microorganisms in both asymptomatic and tobacco brown spot leaves at different persistence periods(0,5,10,and 15 days post-fungicide application)using high-throughput sequencing technology.The results indicated that Jiangong effectively inhibited mycelial growth(average EC_(50) value of 0.51μg/mL),conidia germination(average EC_(50) value of 3.47μg/mL),and the carbon metabolism of A.alternata.Both asymptomatic and symptomatic leaves presented complex microbial communities.Higher fungal diversity was noted in asymptomatic leaves,while higher bacterial diversity was found in symptomatic leaves.After application,the diversity and abundance of microbial community structures in both types of leaves changed over time.Fungal microbiome communities showed greater sensitivity than bacterial groups,with the microbiome communities of asymptomatic leaves being more affected than those of symptomatic leaves.Fungal community diversity decreased for both symptomatic and asymptomatic leaves after 5 days of application,while the diversity of fungal community in symptomatic leaves showed an upward trend after 10 days of application.Meanwhile,bacterial community diversity increased in both symptomatic and asymptomatic leaves after 5 days of application but then declined in asymptomatic leaves after 15 days.The abundance of the dominant function group of phyllosphere bacteria(metabolism,genetic information processing,environmental information processing)was not affected by the application of Jiangong.However,the abundance of the dominant function group of phyllosphere fungi(animal pathogen-endophyte-wood saprotroph,endophyte-plant pathogen,plant pathogen-undefined saprotroph)was significantly affected by the application of Jiangong,and high variation was found in symptomatic leaves than that of asymptomatic leaves.The application of Jiangong-induced alterations in the community structure of the tobacco phyllosphere microbiome provides a basis for future tobacco brown spot control strategies based on phyllospheric microecology.

Evaluation of Resistance of Different Kiwifruit Varieties (Lines) to Canker Disease and Brown Spot Disease

Kiwifruit canker and brown spot are significant diseases affecting kiwis,caused by Pseudomonas syringae patho-genic variations(Pseudomonas syringae pv.Actinidiae(Psa))and Corynesporapolytica(Corynespora cassiicola).At present,the research on canker disease and brown spot disease mainly focuses on the isolation and identification of pathogenic bacteria,drug control,resistance gene mining and functional verification.Practice has proved that breeding disease resistant varieties are an effective method to control canker disease and brown spot disease.However,most existing cultivars lack genes for canker and brown spot resistance.Wild kiwifruit resources in nat-ure exhibit extensive genetic diversity due to prolonged natural selection,containing numerous resistance genes.But,due to insufficient understanding of the resistance of most kiwifruit varieties(lines)to canker disease and brown spot disease,some high-quality resources have not been fully utilized.The incidence of canker and brown spot of 18 kiwifruit cultivars(lines)was measured by inoculating isolated branches and leaves,and their resistance to canker and brown spot was analyzed according to the length,disease index,mean diameter,and systematic clustering.The results were as follows:Among 18 different kiwifruit varieties(lines)for canker disease,there were two highly resistant materials,eight disease-resistant materials,four disease-susceptible materials,and two highly susceptible materials.Moreover,regarding brown spot disease,there were one highly resistant material,five dis-ease-resistant materials,four susceptible materials,and three highly susceptible materials.Furthermore,four resources were resistant to both diseases.The outcomes provided a theoretical basis for breeding kiwifruit against canker and brown spot.

Loss Rate Estimation of Yield and Output Value of Tobacco Leaf Infected by Tobacco Blown Spot (Alternaria alternata)

[Objective] The paper was to study the effect of tobacco blown spot on the yield and output value of tobacco leaf.[Method]The upper,middle and lower leaves in tobacco plant were selected during the harvest period of tobacco to carry out loss rate estimation of yield and output value of tobacco leaf caused by different disease levels of brown spot.Regression correlation analysis was also conducted.[Result]The disease levels of brown spot had extremely significant strong negative correlation with single leaf weight of tobacco leaf,and it had extremely significant strong positive correlation with the loss rate of single leaf weight.The increase speed of loss rate of single leaf weight of middle and upper leaves was obviously faster than that of lower leaves.The loss rates of single leaf weight of upper,middle and lower leaves were 3.18%-28.95%,3.43%-28.88% and 10.07%-26.90%,respectively.The higher the disease level of blown spot was,the lower the yield and output value of tobacco leaf was,and the corresponding loss rate was also higher.Correlation analysis showed that the disease level of blown spot had extremely significant strong negative correlation with the yield and output value of tobacco leaf,and it had extremely significant strong positive correlation with the loss rate of yield and output value.The negative impact of blown spot on the output value of tobacco leaf was far greater than that on the yield.The highest loss rate of the yield of tobacco leaf was 28.56%,while the highest loss rate of output value reached 89.67%.[Conclusion] The study provided theoretical basis for accurately holding the critical period for the control of blown spot,thus reducing the damage on tobacco leaf and improving the output value of tobacco leaf.

Study on Biological Characteristics of the Pathogen of Pistacia vera Leaf Brown Spot

[Objective] The paper was to study the occurrence rule of Pistacia vera leaf brown spot and the biological characteristics of its pathogen.[Method] The occurrence rule of P.vera leaf brown spot was investigated in field.A fungus was isolated and purified from the diseased tissue of P.vera,its cultural trait and morphological characteristics were observed in indoor experiment,and the classification status was identified according to its morphology.The effects of different temperatures on mycelial growth of the pathogen,as well as the effects of different temperatures and humidity on spore germination of the pathogen were also studied.[Result] P.vera leaf brown spot was a fungal disease,which mainly infected the leaves and fruits of P.vera,causing leaf spot and blight.The disease had serious incidence in introduction place of P.vera in China.The fungal disease was identified to be Alternaria alternaria,the appropriate temperature for mycelial growth was 20-25 ℃,the appropriate temperature for spore germination was 25-30 ℃,and the appropriate relative humidity was over 95%.[Conclusion] Late spring and early summer,as well as late summer and early autumn are two peak periods for incidence of the disease,continuous rain in summer is the decisive condition for the infection and outbreak of P.vera leaf brown spot.

Effects of Radix Curcumae Fungicides on Tobacco Brown Spot and Yield of Flue-cured Tobacco Leaves

This study aimed to investigate the effects of Radix Curcumae fungicides on tobacco brown spot and yield of flue-cured tobacco leaves. Through field experi- ments, control efficiency of Radix Curcumae fungicides against tobacco brown spot was investigated. The results showed that the average control efficiency of 400-fold, 600-fold and 800-fold Radix Curcumae fungicides against tobacco brown spot reached 37.83%, 34.09% and 24.32%, respectively. This study could provide the ba- sis for screening and application of plant-derived fungicides against tobacco brown spot.

Characterizing and Estimating Fungal Disease Severity of Rice Brown Spot with Hyperspectral Reflectance Data

Large-scale farming of agriculture crops requires real-time detection of disease for field pest management. Hyperspectral remote sensing data generally have high spectral resolution, which could be very useful for detecting disease stress in green vegetation at the leaf and canopy levels. In this study, hyperspectral reflectances of rice in the laboratory and field were measured to characterize the spectral regions and wavebands, which were the most sensitive to rice brown spot infected by Bipolaris oryzae （Helminthosporium oryzae Breda. de Hann）. Leaf reflectance increased at the ranges of 450 to 500 nm and 630 to 680 nm with the increasing percentage of infected leaf surface, and decreased at the ranges of 520 to 580 nm, 760 to 790 nm, 1550 to 1750 nm, and 2080 to 2350 nm with the increasing percentage of infected leaf surface respectively. The sensitivity analysis and derivative technique were used to select the sensitive wavebands for the detection of rice brown spot infected by B. oryzae. Ratios of rice leaf reflectance were evaluated as indicators of brown spot. R669/R746 （the reflectance at 669 nm divided by the reflectance at 746 nm, the following ratios may be deduced by analogy）, R702/R718, R692/R530, R692/R732, R535/R746, R521/R718, and R569/R718 increased significantly as the incidence of rice brown spot increased regardless of whether it＇s at the leaf or canopy level. R702/R718, R692/R530, R692/R732 were the best three ratios for estimating the disease severity of rice brown spot at the leaf and canopy levels. This result not only confirms the capability of hyperspectral remote sensing data in characterizing crop disease for precision pest management in the real world, but also testifies that the ratios of crop reflectance is a useful method to estimate crop disease severity.

Analysis of Meteorological Condition for Infection of the Pathogen of Tobacco Brown Spot (Alternaria alternate)

[Objective] The paper was to understand the suitable meteorological indexes and key meteorological factors for infection and prevalence of tobacco brown spot. [ Method] Tobacco brown spot disease in five topical mountainous climatic areas of Guizhou Province was investigated, and the difference of biological characteristics of different strains was analyzed indoor. Different meteorological conditions （light, temperature and humidity） were simulated in artificial climate box by using the uniform design method, and the difference of infection ability of Alternaria alternate in different climate zones was analyzed in leaves in vitro by hanging drop method. [ Result] The infection rate of A. alternate in different climate zones of Guizhou Province showed certain difference. In low temperature and mid- die humidity （the humidity is 50% -60%, the temperature is 10 -20 ℃） conditions, the pathogen could infect tobacco leaves, various strains had certain difference, but the difference was small. [ Conclusion] The paper provided theoretical basis for prevalence prediction and control of tobacco brown spot.

Comparative transcriptome profiling of two maize near-isogenic lines differing in the allelic state for bacterial brown spot disease resistance

The bacterial brown spot disease（BBS）, caused primarily by Pseudomonas syringae pv. syringae van Hall（Pss）, reduces plant vigor, yield and quality in maize. To reveal the nature of the defense mechanisms and identify genes involved in the effective host resistance, the dynamic changes of defense transcriptome triggered by the infection of Pss were investigated and compared between two maize near-isogenic lines（NILs）. We found that Pss infection resulted in a sophisticated transcriptional reprogramming of several biological processes and the resistant NIL employed much faster defense responses than the susceptible NIL. Numerous genes encoding essential components of plant basal resistance would be able to be activated in the susceptible NIL, such as PEN1, PEN2, PEN3, and EDR1, however, in a basic manner, such resistance might not be sufficient for suppressing Pss pathogenesis. In addition, the expressions of a large number of PTI-, ETI-, PR-, and WRKY-related genes were pronouncedly activated in the resistant NIL, suggesting that maize employ a multitude of defense pathways to defend Pss infection. Six R-gene homologs were identified to have significantly higher expression levels in the resistant NIL at early time point, indicating that a robust surveillance system（gene-to-gene model） might operate in maize during Pss attacks, and these homolog genes are likely to be potential candidate resistance genes involved in BBS disease resistance. Furthermore, a holistic group of novel pathogen-responsive genes were defined, providing the repertoire of candidate genes for further functional characterization and identification of their regulation patterns during pathogen infection.

Involvement of NAC transcription factor NaNAC29 in Alternaria alternata resistance and leaf senescence in Nicotiana attenuata

NAC-LIKE,ACTIVATED BY AP3/PI(NAP)is a NAC transcription factor regulating leaf senescence in Arabidopsis thaliana.In wild tobacco Nicotiana attenuata,a nuclear localized NAC transcription factor NaNAC29 was identified to be highly elicited after inoculation of Alternaria alternata,a notorious necrotic fungus on tobacco species.The NaNAC29 possesses similar tertiary structure to NAP with 60%amino acid identity.However,it remains unknown the role of NaNAC29 in plant defense responses to A.alternata and leaf senescence in N.attenuata.In this paper,Defensin-like protein 1(NaDLP1)was highly induced in N.attenuata after A.alternata inoculation and bigger lesions were developed in NaDLP1-silenced plants.Interestingly,A.alternata-induced NaDLP1 was reduced by 76%in VIGS NaNAC29 plants and by 61%in JA deficient irAOC plants at 3 days post inoculation.The regulation of NaDLP1 expression by NaNAC29 was clearly independent on JA pathway,since exogenous methyl jasmonate treatment could not complement the induction levels of NaDLP1 in NaNAC29-silenced plants to the levels in WT plants.Otherwise,the expression of NaNAC29 was low expressed in young leaves but highly in senescent leaves and darktreated leaves.NaNAC29-silenced plants,which were generated by virus-induced gene silencing(VIGS NaNAC29),showed delayed senescence phenotype.In addition,constitutive over-expression of NaNAC29 in A.thaliana could rescue the delayed-senescence phenotype of nap and caused precocious leaf senescence of wild-type Col-0 plants.All the data above demonstrate that NaNAC29 is a NAP homolog in N.attenuata participating in the defense responses to A.alternata by regulation of a defensin protein NaDLP1 and promoting leaf senescence.

Rice Leaves Disease Diagnose Empowered with Transfer Learning

In the agricultural industry,rice infections have resulted in significant productivity and economic losses.The infections must be recognized early on to regulate and mitigate the effects of the attacks.Early diagnosis of disease severity effects or incidence can preserve production from quantitative and qualitative losses,reduce pesticide use,and boost ta country’s economy.Assessing the health of a rice plant through its leaves is usually done as a manual ocular exercise.In this manuscript,three rice plant diseases:Bacterial leaf blight,Brown spot,and Leaf smut,were identified using the Alexnet Model.Our research shows that any reduction in rice plants will have a significant beneficial impact on alleviating global food hunger by increasing supply,lowering prices,and reducing production's environmental impact that affects the economy of any country.Farmers would be able to get more exact and faster results with this technology,allowing them to administer the most acceptable treatment available.By Using Alex Net,the proposed approach achieved a 99.0%accuracy rate for diagnosing rice leaves disease.

Preparation of Botanical Pesticide 16% Chijunning Microemulsion

By screening emulsifiers and co-solvents and determining relevant physical and chemical properties, the preparation method for 16% Chijunning micreemulsion was studied in the paper. The best formulation （volume fraction） was as follows： Rad/x phytolaccae extract 4%, Magnolia offtcinalis extract 4%, Xanthium sibiricum extract 8%, DBS-Ca 10%, pesticide emulsifier A 15%, cyclohexanone 20%, water 39%. The microemulsion had better development and market future because of its good stability, low price, use security and environmental protection.

Inhibitory Effects of 12 Chemical Agents against Alternaria alternata

[Objective]The paper was to screen highly efficient fungicides for the prevention and control of tobacco brown spot(Alternaria alternata).[Method]The inhibitory effects of 12 chemical agents against A.alternata were determined indoors by mycelium growth rate method.[Result]Toxicity test showed that 30%kresoxim-methyl·boscalid SC had the best inhibitory effect,with an EC_(50)of 1.05μg/mL,followed by 9%pyraclostrobin CS,with an EC_(50)of 2.09μg/mL.As a broad spectrum protective fungicide,77%copper calcium sulfate WP showed a low sensitivity against A.alternata in the petri dish test since it had a mechanism of action different from that of other chemical agents.[Conclusion]The study lays the foundation for subsequent screening of fungicides for the prevention and control of A.alternata in the field.

Effects of Spraying Plant Extract Mixture on Growth and Development and Diseases of Flue-cured Tobacco

[Objective]The paper was to study the effects of plant extract mixture on growth and development,photosynthetic indexes and disease control of flue-cured tobacco.[Method]Using field test method,a total of five treatments were designed in the test,including T1(control,conven-tional pesticide control),T2(conventional pesticide control+spraying plant extract mixture at 15 and 30 d post transplanting),T3(conventional pesticide control+spraying plant extract mixture at 15,30 and 45 d post transplanting),T4(conventional pesticide control+spraying plant extract mixture at 15,30,45 and 60 d post transplanting),and T5(conventional pesticide control+spraying plant extract mixture at 15,30,45,60 and 75 d post transplanting).In addition,flue-cured tobacco in treatments T2-T5 were sprayed with antiviral agent once at 30 d post transplanting,and sprayed with quality promoting agent at 30 and 75 d post transplanting,respectively.[Result]The agronomic traits and photosynthetic indexes of all treatments were improved by spraying plant extract mixture,and those in T5 treatment were the best.Spraying plant extract mixture had significant control effect on brown spot;the disease index in T5 treatment was the lowest,and the control effect was the best.The results showed that spraying plant extract mixture promoted the growth and development of flue-cured tobacco,reduced the disease index of brown spot,and improved the quality of tobacco leaves.[Conclusion]Spraying plant extract mixture has positive effect on growth and development and disease control of flue-cured tobacco.

Diversity among Isolates of the Tangerine Pathotype of Alternaria alternata

The tangerine pathotype of Alternaria alternata is the aetiological agent of Alternaria brown spot on tangerines. In the state of Paraíba, Brazil, its occurrence on “Dancy” tangerine trees is associated with genetic aspects as well as the influence of environmental conditions on reproduction and dissemination within and between populations. The aim of the present study was to evaluate the diversity of isolates of this pathogen using morphophysiological and molecular markers. For the analysis of mycelial growth and sporulation, 30 isolates from different locations were examined at 24-hour intervals until the seventh day, when the spores were quantified. The 30 isolates were characterised based on molecular markers (ISSR) and genetic similarity (Jaccard index). A factor arrangement was used: 30 isolates, four media (ODA, PDA, LEA and V8), three light regimes (continuous dark, alternating light and continuous light) and three temperatures (15°C, 25°C and 35°C), with 12 repetitions. Groups 1, 2 and 3 presented low genetic variability. Group 4 showed high genetic variability of the isolates obtained from the Massaranduba (state of Paraíba-Brazil) producing region and higher mycelial growth and sporulation of A. alternata. The continuous light regime and the temperature 25°C in PDA and V8 media were the ideal conditions for the mycelial growth and sporulation, respectively, of the isolates of A. alternata.

Characterization of the Rice Canopy Infested with Brown Spot Disease Using Field Hyperspectral Data

Based on the field hyperspectral data from the analytical spectral devices （ASD） spectrometer, we characterized the spectral properties of rice canopies infested with brown spot disease and selected spectral regions and bands sensitive to four severity degrees （severe, moderate, light, and healthy）. The results show that the curves＇ variation on the original and the first- and second-order de- rivative curves are greatly different, but the spectral difference in the near-infrared region is the most obvious for each level. Specifically, the peaks are located at 822, 738, and 793 nm, while the valleys are located at 402, 570, and 753 run, respectively. The sensitive regions are between 430-520, 530-550, and 650-710 nm, and the bands are 498, 539, and 673 nm in the sensitivity analysis, while they are in the ranges of 401-530, 550-730 as well as at 498 nm and 678 nm in the continuum removal.