Bacterial Blight Disease Research Articles

Screening of Rice Genotypes for Resistance Against Bacterial Blight Disease

A study was undertaken at V. C. Farm, Mandya, Karnataka, India during 2020 to screen the genotypes against BLB under natural field conditions. Host Plant resistance is an important component of an integrated management program for this disease. Among the 102 rice genotypes screened under natural epiphytotic condition at Zonal Agricultural Station, V. C. Farm, Mandya, none of them were found immune against bacterial leaf blight. So, in the study, plants were assessed by measuring disease severity (% of leaf diseased) and area under the disease progress curve (AUDPC). The pathogenicity of Xoo was tested on IRRI rice cultivars, inoculation was conducted at the maximum tillering stage, and the lesion length was measured after 14 days of inoculation. An attempt was made to phenotypically characterize a set of 102 Genotypes from IRRI for BLB resistance by artificially inoculaton using clipping method. Out of the 102 genotypes and two checks tested, it was observed that five entries viz., IRGC 125853, IRGC 126264, IRGC 132357, IRGC 122088 IRGC 125658 and Improved Samba Mahsuri were highly resistant with score of 1. Only one entry (IRGC 125754) was resistant with score of 3, 33 lines being moderately resistant with score of 5 and 43 lines were susceptible with score of 7. 20 lines and also the susceptible check Jyothi-PTB 39, had the highest susceptibility with a phenotypic score of 9.

Bactericidal bissulfone B7 targets bacterial pyruvate kinase to impair bacterial biology and pathogenicity in plants.

The prevention and control of rice bacterial leaf blight (BLB) disease has not yet been achieved due to the lack of effective agrochemicals and available targets. Herein, we develop a series of novel bissulfones and a novel target with a unique mechanism to address this challenge. The developed bissulfones can control Xanthomonas oryzae pv. oryzae (Xoo), and 2-(bis(methylsulfonyl)methylene)-N-(4-chlorophenyl) hydrazine-1-carboxamide (B7) is more effective than the commercial drugs thiodiazole copper (TC) and bismerthiazol (BT). Pyruvate kinase (PYK) in Xoo has been identified for the first time as the target protein of our bissulfone B7. PYK modulates bacterial virulence via a CRP-like protein (Clp)/two-component system regulatory protein (regR) axis. The elucidation of this pathway facilitates the use of B7 to reduce PYK expression at the transcriptional level, block PYK activity at the protein level, and impair the interaction within the PYK-Clp-regR complex via competitive inhibition, thereby attenuating bacterial biology and pathogenicity. This study offers insights into the molecular and mechanistic aspects underlying anti-Xoo strategies that target PYK. We believe that these valuable discoveries will be used for bacterial disease control in the future.

Establishment of Functional PCR-Based Markers against Bacterial Leaf Blight Disease in Rice Landraces of Yunnan Province of China.

Bacterial leaf blight is a devastating disease of rice worldwide. The resistant genes are routinely transferred from landraces to cultivated varieties through backcross breeding along with marker-assisted selection. In the present study, we use the gene-specific markers to screen the rice landraces in Yunnan Province of China. We collected 404 representative samples of 24 different rice landraces from Yunnan Province of China. The initial PCR-based screening suggested that the leaf blight resistance was not evenly distributed in Yunnan Province. Our results indicate that there is a complete loss of resistance for landraces based on xa5 and xa13 genes. On the other hand, landraces harboring Xa7 and Xa21 showed a high level of resistance. Using gene-specific PCR-based data, we were able to identify the resistant, susceptible and heterozygous populations across Yunnan Province. The widely used Xa21 gene alone showed a remarkable level of resistance throughout the province, indicating its potential to develop broad-spectrum resistance in rice germplasm. The key aspects of bacterial blight spread according to local sites in Yunnan Province and the resistance conferred by different landraces due to the presence of different resistance genes are discussed.

Performance Analysis of Deep Transfer Learning Models for the Automated Detection of Cotton Plant Diseases

Cotton is one of the most important agricultural products and is closely linked to the economic development of Pakistan. However, the cotton plant is susceptible to bacterial and viral diseases that can quickly spread and damage plants and ultimately affect the cotton yield. The automated and early detection of affected plants can significantly reduce the potential spread of the disease. This paper presents the implementation and performance analysis of bacterial blight and curl virus disease detection in cotton crops through deep learning techniques. The automated disease detection is performed through transfer learning of six pre-trained deep learning models, namely DenseNet121, DenseNet169, MobileNetV2, ResNet50V2, VGG16, and VGG19. A total of 1362 images of local agricultural fields and 1292 images from online resources were used to train and validate the models. Image augmentation techniques were performed to increase the dataset diversity and size. Transfer learning was implemented for different image resolutions ranging from 32×32 to 256×256 pixels. Performance metrics such as accuracy, precision, recall, F1 Score, and prediction time were evaluated for each implemented model. The results indicate higher accuracy, up to 96%, for DenseNet169 and ResNet50V2 models when trained on the 256×256 pixels image dataset. The lowest accuracy, 52%, was obtained by the MobileNetV2 model when trained on low-resolution, 32×32, images. The confusion matrix analysis indicates the true-positive prediction rates higher than 91% for fresh leaves, 87% for bacterial blight, and 76% for curl virus detection for all implemented models when trained and tested on an image dataset of 128×128 pixels or higher resolution.

Application of endophytic bacterium Bacillus velezensis BTR11 to control bacterial leaf blight disease and promote rice growth

BackgroundBacterial leaf blight (BLB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most destructive pathogens responsible for severe yield losses in rice. Application of bacterial biocontrol agent (BCA) with plant growth promotion (PGP) abilities is a promising method that alternates current conventional practices to manage BLB disease and increase crop yield. Hence, this study aimed to isolate and identify BCA with PGP abilities from internal plant tissues and rhizosphere soil of healthy and Xoo-infected rice and evaluate their antagonistic and PGP properties under greenhouse and field conditions.ResultsA total of 14 bacterial isolates were isolated and presented in vitro antagonistic ability against the Xoo. The rice endophytic bacterium strain Bacillius velezensis (BTR11) had the highest antagonistic activity against the Xoo, produced indole acetic acid (IAA), and mineralized nutrients (K and P). The greenhouse experiment revealed that culture broth of strain BTR11 had a high protective effect (72.1%) against the BLB when applied at the protective-fighting mode, i.e., before and after the Xoo infection. Preliminary results of the field experiment showed that a protective effect against the bacterial blight disease was obtained as high as 75–85%, if the strain was used as an additive to the soil for the seedlings in combination with spraying when the disease began in the field. In addition, using the strain BTR11 also increased the rice yield to about 12% more than the un-treatment control.ConclusionsThe study showed a significant potential for the application of endophytic bacteria in controlling BLB disease, while stimulating plant growth, thus reducing the use of agrochemicals in rice cultivation.

Marker-assisted enhancement of bacterial blight (Xanthomonas oryzae pv. oryzae) resistance in a salt-tolerant rice variety for sustaining rice production of tropical islands.

Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae is a major disease of rice, specially in the tropical regions of the world. Developing rice varieties with host resistance against the disease is the most effective and economical solution for managing the disease. Pyramiding resistance genes (Xa4, xa5, xa13,and Xa21) in popular rice varieties using marker-assisted backcross breeding (MABB) has been demonstrated as a cost-effective and sustainable approach for establishing durable BB resistance. Here, we report our successful efforts in introgressing four resistance genes (Xa4, xa5, xa13, and Xa21) from IRBB60 to CARI Dhan 5, a popular salt-tolerant variety developed from a somaclonal variant of Pokkali rice, through functional MABB. Both BB and coastal salinity are among the major challenges for rice production in tropical island and coastal ecosystems. Plants with four, three, and two gene pyramids were generated, which displayed high levels of resistance to the BB pathogen at the BC3F2 stage. Under controlled salinity microplot environments, the line 131-2-175-1223 identified with the presence of three gene pyramid (Xa21+xa13+xa5) displayed notable resistance across locations and years as well as exhibited a salinity tolerance comparable to the recurrent parent, CARI Dhan 5. Among two BB gene combinations (Xa21+xa13), two lines, 17-1-69-334 and 46-3-95-659, demonstrated resistance across locations and years, as well as salt tolerance and grain production comparable to CARI Dhan 5. Besides salinity tolerance, five lines, 17-1-69-179, 46-3-95-655, 131-2-190-1197, 131-2-175-1209, and 131-2-175-1239, exhibited complete resistance to BB disease. Following multilocation testing, potential lines have been identified that can serve as a prospective candidate for producing varieties for the tropical Andaman and Nicobar Islands and other coastal locations, which are prone to BB and coastal salinity stresses.

Genetic diversity of INGER rice genotypes based on morphological charac-ters and bacterial blight resistance

Bacterial blight disease (causal organism: Xanthomonas oryzae pv. oryzae) is an economically significant menace to rice cultivation in Bangladesh as well as in the world, which reduces significant yield loss in rice and hampers food security. The most sustainable strategy to fight this disease is the adoption of disease-resistant cultivars. The morphological trait and nature of diversity of 92 bacterial blight-resistant INGER (International Network for Genetic Evaluation of Rice) genotypes collected from the International Rice Research Institute (IRRI, Philippines) were analyzed to explore for sources of resistance. Artificial inoculation by BXO9, a virulent race of Xoo was used to evaluate and screen those genotypes in the field. Twelve genotypes, out of 92 had resistance, and another twelve had moderately resistance. Eleven morphological traits including disease data of each genotype were recorded and found noticeable diversity among the genotypes. Pearson’s correlation analysis among genotypes revealed that yield per hill is positively correlated with number of tiller per hill, number of effective tiller per hill, number of spikelets per panicle, number of filled spikelets per panicle and thousand grain weight. In cluster analysis, 15 major groups were obtained in ninety-two rice genotypes by using Euclidean distance and the UPGMA method. Cluster-1 comprises single genotypes SVIN310 which showed resistant reaction to bacterial blight disease had the highest tiller number, effective tiller number, number of spikelets per panicle, filled spikelets per panicle and thousand-grain weight. In PCA analysis, the first four principal components narrated around 77.32% variation. Among ninety-two genotypes, G1 (SVIN310), G23 (SVIN018), G70 (SVIN012), G75 (SVIN054), G33 (SVIN007), G48 (SVIN006), G80 (SVIN049), G90 (BRRI dhan84), G30 (SVIN290) near to the vector line of yield per hill are highly and positively responsive to the yield per hill. Considering all of these, cluster-1 having genotype SVIN310 with resistant phenomena would be the potential genotype for further use in a breeding program. Bangladesh Rice J. 26 (1): 17-31, 2022

The role of biofertilizer “Mikrobat” as a stimulator to increase productivity and health of rice plants

Biofertilizer Mikrobat (Patent Certificate: No. IDP000059255 and Brand Certificate: No. IDM000613360) is a bacterial consortium containing four superior microbes, including Azotobacter sp. isolate AP08, Pseudomonas sp. isolate PP012, Lactobacillus sp. isolate LP032, and Streptomyces sp. isolate SP022 with their respective roles as nitrogen fixers, Phosphate and Potassium solvents, providers of auxin, cytokinins, vitamins, amino acids, and antibiotics. This biotechnological product can be used to loosen and nourish the soil, increase the activity of positive microorganisms in the ground, increase seed vigor, suppress plant pests and diseases, accelerate plant growth and improve production and yield quality. The results of trials on rice plantations in the Experimental farm of BPTPH Maros showed that the treatment of Mikrobat has the best results in suppressing bacterial leaf blight and blast diseases and increasing rice plant production. The intensity of BLB disease and blast on Brang Biji (hybrid variety) of 0% and 0.5% compared to controls 8% and 2%, respectively. The highest number of tillers reached 19.02 tiller than control with 13.98, while production achieved 12.74 tonnes/ha compared to the control 9.42 tonnes/ha.

Fine mapping and sequence analysis reveal a promising candidate gene encoding a novel NB-ARC domain derived from wild rice (Oryza officinalis) that confers bacterial blight resistance.

Bacterial blight disease of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most serious constraints in rice production. The most sustainable strategy to combat the disease is the deployment of host plant resistance. Earlier, we identified an introgression line, IR 75084-15-3-B-B, derived from Oryza officinalis possessing broad-spectrum resistance against Xoo. In order to understand the inheritance of resistance in the O. officinalis accession and identify genomic region(s) associated with resistance, a recombinant inbred line (RIL) mapping population was developed from the cross Samba Mahsuri (susceptible to bacterial blight) × IR 75084-15-3-B-B (resistant to bacterial blight). The F2 population derived from the cross segregated in a phenotypic ratio of 3: 1 (resistant susceptible) implying that resistance in IR 75084-15-3-B-B is controlled by a single dominant gene/quantitative trait locus (QTL). In the F7 generation, a set of 47 homozygous resistant lines and 47 homozygous susceptible lines was used to study the association between phenotypic data obtained through screening with Xoo and genotypic data obtained through analysis of 7K rice single-nucleotide polymorphism (SNP) chip. Through composite interval mapping, a major locus was detected in the midst of two flanking SNP markers, viz., Chr11.27817978 and Chr11.27994133, on chromosome 11L with a logarithm of the odds (LOD) score of 10.21 and 35.93% of phenotypic variation, and the locus has been named Xa48t. In silico search in the genomic region between the two markers flanking Xa48t identified 10 putatively expressed genes located in the region of interest. The quantitative expression and DNA sequence analysis of these genes from contrasting parents identified the Os11g0687900 encoding an NB-ARC domain-containing protein as the most promising gene associated with resistance. Interestingly, a 16-bp insertion was noticed in the untranslated region (UTR) of the gene in the resistant parent, IR 75084-15-3-B-B, which was absent in Samba Mahsuri. The association of Os11g0687900 with resistance phenotype was further established by sequence-based DNA marker analysis in the RIL population. A co-segregating PCR-based INDEL marker, Marker_Xa48, has been developed for use in the marker-assisted breeding of Xa48t.

Evaluation of different antimicrobial agents for laboratory and field against Pantoea agglomerans, the causative agent of bacterial leaf blight disease on oat (Avena sativa)

AbstractLeaf blight disease (LBD) caused by Pantoea agglomerans is a newly emerged oat disease in China that causes great economic and yield losses of oat production. Laboratory and field experiments were conducted to evaluate the efficacy of 13 antimicrobial agents against P. agglomerans and recommend agents with better control efficacy for use. The antibacterial potential of four concentrations of each agent was evaluated under in vitro conditions. Zhongshengmycin and ethylicin were the most effective in inhibiting the growth of P. agglomerans; their bacteriostatic rates (85.0% and 84.8%, respectively) were higher while EC50 lower (0.31 and 0.90, respectively) than other agents. The greenhouse and field experiment suggested that the greatest fresh weight per plant (57.26 g and 57.93 g), forage yield (22.53 t/ha and 22.21 t/ha) and control efficacy (>75%) were obtained after spraying twice with zhongshengmycin or ethylicin in the LBD occurrence phase, with lower yields and control by kasugamycin + dicopper chloride trihydroxide, kasugamycin + oxine copper, benziothiazolinone, copper hydroxide, phenanthrenecarboxylicacid, copper, picoxystrobin, chloroisobromine cyanuric acid, oxathiapiprolin or azoxystrobin. Foliar application of zhongshengmycin or ethylicin can therefore be used for the effective management of LBD of oat.

Hedychium coronarium flower extract modulates rice plant photosystem II and antioxidant enzymes activity to induce resistance against bacterial blight

Rice Bacterial Blight (BB), which is caused by Xanthomonas oryzae pv. oryzae (Xoo), is deemed as one of the most severe diseases that can afflict rice crops. Agricultural practices have often relied upon bactericides to reduce BB infections. The excessive utilization of conventional bactericides in past years has led to environmental contamination and elevated bacterial resistance. However, plant elicitors are ecologically safe biological pesticides, have been demonstrated to enhance plant disease resistance by inducing defense-related enzymes and restoring photosynthetic efficiency. We tested the efficacy of Hedychium coronarium methanol extract (ME) and aqueous extract (AE) and found that they improved protection against BB disease by inducing resistance to the pathogen. However, the control group exhibited significantly higher membrane damage due to greater Xoo infections and necrosis. Additionally, the occurrence of various antimicrobial compounds was identified in the extract by using the gas chromatography-mass spectrometry (GC-MS). Subsequently, the in vitro antibacterial property of the extract was confirmed, as the higher zone of inhibition was observed with ME against Xoo. Molecular docking study further revealed that certain metabolites, such as mucic acid and 3-phenyllactic acid of H. coronarium, could target the d-alanine d-alanine ligase A (DdlA) and Peptide deformylase (PDF) proteins of Xoo, thereby hindering its growth. Thus, priming rice plants with H. coronarium flower extract could induce defense responses by modulating photosystem II and enzymatic antioxidants. Therefore, it could be a promising source of antimicrobial metabolites.

Potential of Bacillus spp. Isolated from Food Waste Compost for Controlling Rice Diseases

Bacterial leaf blight, bakanae and blast are severe, economically damaging rice diseases caused by Xanthomonas oryzae, Fusarium fujikuroi, and Magnaporthe oryzae, respectively. Bacillus spp. have been applied as bioactive, eco-friendly agents to control these diseases. In this study, five antagonistic strains isolated from food waste compost, namely B. subtilis strain BS, B. amyloliquefacien strain C2-1, B. tequilensis strain 1-BA, B. licheniformis strain 2-BA, and Lysinibacillus. sp strain 3-BA were tested for their efficacy againstrice diseases. The inhibition of X. oryzae was tested by paper disc diffusion, while the inhibitions of F. fujikuroi and M. oryzae were tested in dual cultures. It was found that B. amyloliquefacien strain C2-1 gave the widest clear zones. At 24 h, 48 h, 72 h and 7 days, the strain had produced zones of inhibition against X. oryzaeof 7.41±0.65, 7.9±0.20, 8.8±0.65 and 8.90±0.12 mm, respectively. B. amyloliquefacien strain C2-1 also reduced the growth of the fungal rice pathogens F. fujikuroi and M. oryzae, achieving 98.79% and 97.74% inhibitions, respectively. B. amyloliquefaciens strain C2-1 was also effective against X. oryzae, F. fujikuroi, and M. oryzae in the greenhouse. Fourteen days after spraying rice plants with the B. amyloliquefacien strain C2-1, infections with X. oryzae, F. fujikuroi, and M. oryzae were inhibited by 60%, 37%, and 25%, respectively. The results suggested that B. amyloliquefacien strain C2-1 can be used as a biocontrol agent against bacterial leaf blight, bakanae, and rice blast diseases.

Identification of Blast Resistant Breeding Lines through Uniform Blast Nursery in Rice (Oryza sativa L.)

Rice blast disease caused by the fungus Magnaporthe oryzae is the most devastating disease of rice causing considerable yield losses. Development of resistant varieties is the most effective and environment friendly strategy to combat losses. RNR 15048 (Telangana sona) (IET23746) is a popular local variety possessing a desirable, short-slender grain type with low glycemic index, good cooking quality and having Pi2 gene for blast. However, it is moderately susceptible to bacterial blight disease and having no durable resistance to blast disease with weak culm. In this context, improvement of RNR 15048 for blast, bacterial leaf blight is important to reduce yield losses. Present study was carried out to screen and identify blast resistant breeding lines in Rice at Regional Agricultural Research station, Polasa, Jagtial, PJTSAU during Rabi, 2022-2023. 18 F3 breeding lines were screened in uniform blast nursery along with parents RNR 15048, MTU 1010 NILs, ISM NILs. TN1 and NLR 34449 were used as the susceptible and resistant checks, respectively for screening blast resistance. Screening was done by following 0-9 Standard Evaluation Scale (SES) for leaf blast. Among the studied 18 F3 breeding lines 12 lines were found resistant with score of 3 and 6 lines were found moderately resistant to screening reaction with score of 5. TN1 showed highly susceptible reaction with score of 9 and NLR 34449 showed highly resistant reaction with score of 1.

Potential of Indigenous Rhizobacteria as Biocontrol Agents of Xanthomonas sp.

Bacterial leaf blight (BLB) disease caused by Xanthomonas sp. is one of the main diseasesof eucalypt plants. The utilization of rhizobacteria to manage diseases in other agriculturalecosystems has been reported. This study aims to select and characterize rhizobacteria fromthe rhizospheric zones of Eucalyptus pellita with antagonistic nature against Xanthomonas sp.and to identify isolates that have the best potential as biocontrol agents in the Eucalyptus–Xanthomonas pathosystem. The research was conducted in-vitro. The antagonism test wasarranged in a completely randomized design with three replications. Characteristics ofantagonistic rhizobacteria were examined based on their ability as plant growth-promotingbacteria (PGPR). Identification of potential rhizobacteria was performed based on 16S rRNAsequences. There were 14 isolates showing antagonistic activities against Xanthomonas sp. Theresults showed that the rhizobacteria had significant antagonistic impacts against the pathogen.Characterization of the 14 isolates indicated that all isolates produced siderophores and indoleacetic acid (IAA). As many as 13 isolates produced protease, eight isolates were able to dissolvephosphate, and three isolates synthesized hydrogen cyanide (HCN). The isolate with the highestinhibitory effect was isolate RE081, whose activity was classified as very strong. The RE81isolate also showed the best properties in the HCN test (+++), IAA production (19,29 mg L–1),and the ability to dissolve phosphates. Molecular analysis of the 16S rRNA gene disclosed thatRE81 is Pseudomonas aeruginosa (100%).

Assessing Paddy Field Health Using High-Resolution Multi-Spectral Camera in Subang Indonesia to Implement Precision Agriculture 4.0

Increasing yield and improving the sustainability of agriculture are needed through data-driven precision agriculture technology. Multispectral sensor measures the light reflected from the plant canopy and generates a reflectance value that indicates the difference between healthy and stressed plants. We use precision agriculture to assess paddy field health in Subang Regency, West Java, Indonesia, especially early detection of bacterial leaf blight and stem borer disease. The condition of the study area has a relatively flat topography, with the Grendel glutinous paddy variety, and has a late vegetative to early generative phase. The data was gathered using an unmanned aerial vehicle (UAV) fitted with a MicaSense Red Edge-P sensor to obtain multispectral images. We employed Normalized Difference Red Edge Index (NDRE) to create a health model and validated using 70 field sampling locations. As a result, accuracy detection was 90% hence the use of UAV technology can be used for early disease detection. We classified the paddy field as healthy and unhealthy in percentage through spectral analysis and data from validation. This research has proven that we could detect disease in paddy fields faster and more efficiently. Utilizing UAVs for precision agriculture will prevent crop failure and increase food security in Subang and Indonesia. However, the limitation of this study is weather conditions and should consider plant varieties.

Screening of recombinant inbred lines for resistance to bacterial leaf blight pathotypes in rice (Oryza sativa L.)

In the present investigation 16 recombinant inbred lines (RIL’s) developed from the intra-specific cross between YH3 and AKDRMS 21-54 through Marker Assisted Pedigree Breeding Method were screened along with their parents and the checks, namely, BPT 5204, TN1 and Improved Samba Mahsuri (ISM) against IxoPt-20 pathotype at the ICAR-Indian Institute of Rice Research, Hyderabad during Rabi 2021-22 and a new pathotype of Xanthomonas oryzae pv. oryzae causing Bacterial Leaf Blight disease in rice at Regional Agricultural Research Station, Maruteru during Kharif 2022 to identify pathotype specific resistant sources. Morpho-Molecular screening was adopted to evaluate the recombinant inbred lines over two locations in the consecutive seasons of Rabi 2021-22 and Kharif 2022. Based on per cent diseased leaf area, the genotypes were scored and categorised as per the Standard Evaluation System (SES) scale provided by International Rice Research Institute (IRRI). The results revealed all 16 RIL’s to be either resistant (10) or moderately resistant (6) to IxoPt-20 pathotype. However, only five RIL’s were found to be resistant, while four RIL’s were moderately resistant for the new virulent pathotype. Seven RIL’s with resistant to moderately resistant reaction for IxoPt-20 pathotype, showed moderately susceptible reaction for the new virulent pathotype. Among the resistant RIL’s identified for each pathotype, BPT-1901-72-10-6, BPT-1901-108-4-1 and BPT-1901-111-3-2 were found to be uniformly resistant, while, BPT-1901-45-8-6 and BPT-1901-163-1-18 were uniformly moderately resistant to both IXoPt-20 and the new virulent pathotype at Hyderabad and Maruteru, respectively, indicating their potential as genetic stocks for development of new cultivars resistant to bacterial leaf blight disease.

Evaluation of Genotypes against Bacterial Blight and Tobacco Streak Virus Diseases in Cotton

Cotton screening was conducted at the Regional Agricultural Research Station (RARS) in Warangal, Telangana, India. The experimental material consisted of 52 cotton germplasms and 13Bt cotton hybrids with a check were tested against bacterial blight and tobacco streak virus diseases duringKharif-2016 at RARS,Warangal. Out of 52 cotton germplasms,17 entries viz.,HYPS-152,H-1250,RAH-4,KH-2244N,LH-900,SA-434,RAH-12,JK-354,GBHU-164,NA-340,BS-37,TCH-724, ICMF-23,ICMF-20,SA-1004,ARB-89001 and BB-2 were found resistant to bacterial blight disease and eighteen entries namely.,SA-53-1,RHH-101,KH-2244N,KH-134,TCH-1649,NH-557,IH-08,PH-1008,TCH-724,JK-205,MRK-38,LH-2170,AKH-2822,ARB-8901,G-COT-10,JK2764,CCH 1071 and CCH-11germplasms were noticed tobacco streak virus disease rating scale 0 (Immune). Out of 13 Bt cotton hybrids , two entries viz., Balhwan and Raja were moderately resistant to bacterial blight disease and eleven entries namely viz., Bhakti, Raja, Balhwan, Akka, First class,RCH-812,Ankur-3224,ACH-199,RCH-836,RCH-812 and ATM entries were showed disease rating scale 1(resistant) to tobacco streak virus disease.

Discovery of Novel Pentacyclic Triterpene Acid Amide Derivatives as Excellent Antimicrobial Agents Dependent on Generation of Reactive Oxygen Species.

Developing new agricultural bactericides is a feasible strategy for stopping the increase in the resistance of plant pathogenic bacteria. Some pentacyclic triterpene acid derivatives were elaborately designed and synthesized. In particular, compound A22 exhibited the best antimicrobial activity against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac) with EC50 values of 3.34 and 3.30 mg L-1, respectively. The antimicrobial mechanism showed that the compound A22 induced excessive production and accumulation of reactive oxygen species (ROS) in Xoo cells, leading to a decrease in superoxide dismutase and catalase enzyme activities and an increase in malondialdehyde content. A22 also produced increases in Xoo cell membrane permeability and eventual cell death. In addition, in vivo experiments showed that A22 at 200 mg L-1 exhibited protective activity against rice bacterial blight (50.44%) and citrus canker disease (84.37%). Therefore, this study provides a paradigm for the agricultural application of pentacyclic triterpene acid.

A laudable strategy to manage bacterial panicle blight disease of rice using biocontrol agents.

Bacterial panicle blight (BPB) disease is a dreadful disease in rice-producing countries. Burkholderia glumae, a Gram-negative, rod-shaped, and flagellated bacterium was identified as the primary culprit for BPB disease. In 2019, the disease was reported in 18 countries, and to date, it has been spotted in 26 countries. Rice yield has been reduced by up to 75% worldwide due to this disease. Interestingly, the biocontrol strategy offers a promising alternative to manage BPB disease. This review summarizes the management status of BPB disease using biological control agents (BCA). Bacteria from the genera Bacillus, Burkholderia, Enterobacter, Pantoea, Pseudomonas, and Streptomyces have been examined as BCA under in vitro, glasshouse, and field conditions. Besides bacteria, bacteriophages have also been reported to reduce BPB pathogens under in vitro and glasshouse conditions. Here, the overview of the mechanisms of bacteria and bacteriophages in controlling BPB pathogens is addressed. The applications of BCA using various delivery methods could effectively manage BPB disease to benefit the agroecosystems and food security.

Design, Synthesis, Antibacterial Activity, and Mechanism of Novel Mesoionic Compounds Based on Natural Pyrazole Isolated from an Endophytic Fungus Colletotrichum gloeosporioides.

Xanthomonas oryzae pv. oryzicola (Xoo) is a type of bacteria that causes bacterial leaf blight disease in rice plants. This disease is substantially harmful, and the current prevention and control measures are facing challenges. This study has investigated the effectiveness of the control activity that the endophytic fungus NS7 fermented from Dendrobium candidum possessed against Xoo. Twenty-eight novel mesoionic compounds were designed and synthesized based on the natural compound D. These compounds displayed moderate to excellent anti-Xoo activity in vitro. Notably, compound 24 exhibited prominent anti-Xoo activity in vitro with an EC50 value of 40.3 mg/L, which was better than that of the positive control thiodiazole copper (TC)(71.2 mg/L) and the lead compound D (108.1 mg/L). In vivo pot experiments on Xoo showed that compound 24 exhibited protective and curative activities of 39.4 and 30.4%, respectively, which were better than those of TC (35.7 and 28.8%, respectively). Further, a preliminary mechanism study indicated that compound 24 could enhance the activity of defense enzymes to improve the ability for anti-Xoo. Meanwhile, compound 24 could also regulate the carbon fixation in photosynthetic organisms, which might be related to the enhanced immune function of rice. This study offers a new strategy for discovering antibacterial agents based on natural products.