Xanthomonas Oryzae Pv Research Articles

Antibacterial Activity of Novel 18β-Glycyrrhetinic Hydrazide or Amide Derivatives

Through a facile structural modification on the natural bioactive ingredient 18β-glycyrrhetinic acid(GA), a series of novel GA hydrazide or amide derivatives was obtained, and their final molecular frameworks were characterized by NMR and HRMS analysis. Antibacterial bioassays revealed that some of the GA hydrazide or amide derivatives were able to suppress the growth of three tested plant pathogens. Particularly, compound 3c exhibited excellent in vitro activity against Xanthomonas oryzae pv. Oryzae (Xoo), Pseudomonas syringae pv. actinidiae(Psa), and Xanthomonas axonopodis pv. citri(Xac), providing the EC50 values of 5.89, 16.1, and 3.64 µg/mL, respectively. The data were better than those of the positive controls thiodiazole copper(92.7, 77.8, and 89.9 µg/mL, respectively) and bismerthiazol(31.1, 125.6, and 77.4 µg/mL, respectively). In addition, in vivo experiments suggested that, compared with thiodiazole copper(41.93% and 39.73%, respectively), compound 3c exerted prominently curative and protective activities against rice bacterial leaf blight at 200 µg/mL with the control effects of 52.36% and 51.40%, respectively. Given these obtained results, GA hydrazide or amide derivatives could serve as the feasible leads for exploring highly bioactive substrates.

Xa7, a new executor R gene that confers durable and broad-spectrum resistance to bacterial blight disease in rice

Bacterial blight (BB) is a globally devastating rice disease caused by Xanthomonas oryzae pv. oryzae (Xoo). The use of disease resistance (R) genes in rice breeding is an effective and economical strategy for the control of this disease. Nevertheless, a majority of R genes lack durable resistance for long-term use under global warming conditions. Here, we report the isolation of a novel executor R gene, Xa7, that confers extremely durable, broad-spectrum, and heat-tolerant resistance to Xoo. The expression of Xa7 was induced by incompatible Xoo strains that secreted the transcription activator-like effector (TALE) AvrXa7 or PthXo3, which recognized effector binding elements (EBEs) in the Xa7 promoter. Furthermore, Xa7 induction was faster and stronger under high temperatures. Overexpression of Xa7 or co-transformation of Xa7 with avrXa7 triggered a hypersensitive response in plants. Constitutive expression of Xa7 activated a defense response in the absence of Xoo but inhibited the growth of transgenic rice plants. In addition, analysis of over 3000 rice varieties showed that the Xa7 locus was found primarily in the indica and aus subgroups. A variation consisting of an 11-bp insertion and a base substitution (G to T) was found in EBEAvrXa7 in the tested varieties, resulting in a loss of Xa7 BB resistance. Through a decade of effort, we have identified an important BB resistance gene and characterized its distinctive interaction with Xoo strains; these findings will greatly facilitate research on the molecular mechanism of Xa7-mediated resistance and promote the use of this valuable gene in breeding.

Expression of defense related enzymes in rice near isogenic lines IRBB4 and IRBB7 challenged with Xanthomonas oryzae pv. oryzae at elevated temperature

Expression of defense related enzymes in rice near isogenic lines IRBB4 and IRBB7 challenged with Xanthomonas oryzae pv. oryzae at elevated temperature

Field screening of rice (Oryza sativa L.) genotypes for resistance to bacterial leaf blight (Xanthomonas oryzae pv. oryzae) disease

Rice is the most important crop in Nepal followed by maize and wheat in terms of area (1.4 million ha), production (5.15 million) and productivity (3.5 mt/ha). Bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv. oryzae is considered to be the most widespread and destructive disease of rice in both irrigated and rainfed environments in Nepal. Use of host plant resistance is the most feasible and economical way to combat this disease. However, breakdown of resistance of a variety often occurs after few years of release due to genetic adaptation of the pathogen. Regular screening of the genotypes is utmost for developing the resistant genotypes. Considering the point, this investigation effort has been made to screen the rice genotypes against BLB under natural field condition at Khajura, Banke during 2018 and 2019. In the study, plants were assessed by measuring disease severity (percentage of leaf diseased) and area under the disease progress curve (AUDPC). Differences in resistance among the rice genotypes were observed in both of the tested year. Among the screened 150 rice genotypes during 2018, 6 genotypes scored resistant (R), 81 moderately resistant (MR), 59 moderately susceptible (MS) and 4 susceptible (S) to BLB. Whereas, in 2019, among the tested 315 rice genotypes, none of the genotypes were resistant, 183 MR, 131 MS and 1 S to BLB disease. This showed that the tested genotypes were composed of different genetic background.

Linkage analysis of rice bacterial blight resistance gene xa20 in XM6, a mutant line from IR24.

Bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is an important disease constraining rice (Oryza sativa L.) production worldwide. The XM6 line was induced by N-methyl-N-nitrosourea from IR24, an Indica cultivar that is susceptible to Philippine and Japanese Xoo races. XM6 was confirmed to carry a recessive gene named xa20, resistant to six Philippine and five Japanese Xoo races. The chromosomal gene location was found using 10 plants with the shortest lesion length in an F2 population consisting of 298 plants from a susceptible Japonica variety Koshihikari × XM6. Analysis using PCR-based DNA markers covering the whole rice genome indicated the gene as located on the distal region of the long arm of chromosome 3. The IKC3 line carries IR24 genetic background with Koshihikari fragment on chromosome 3 where a resistance gene was thought to be located. The F2 population from IKC3 × XM6 clearly showed a bimodal distribution separating resistant and susceptible plants. Further linkage analysis conducted using this F2 population revealed that xa20 is located within the 0.8 cM region flanked by DNA markers KIC3-33.88 (33.0 Mb) and KIC3-34.06 (33.2 Mb). This study yields important findings for resistance breeding and for the genetic mechanism of Xoo resistance.

English

Bacterial leaf blight (BLB) is a disease caused by Xanthomonas oryzae pv. oryzae (Xoo) of rice in rice-producing countries including Indonesia and attack rice in all stages of growth. In the advanced, crop production will be decreased by up to 50–70%. Recently, the practical efforts to overcome the problem by using resistant varieties, antibiotics, and sanitation; however, the ability of the pathogen to forms the new virulent pathotypes is noteworthy. Alternatively, the pathogen could be environmental-friendly controlled by utilizing bacteriophages as biological control agents because of their specific characteristics to their bacterial hosts. This research aimed to obtain information about the characteristic of the first isolated bacteriophages from Indonesia. The result showed that two bacteriophages had been isolated from soil in Arjasa Jember and soil in Gadingan Situbondo, namely phage XooX1IDN and phage XooX2IDN, respectively. The two phages were inactivated at 80ºC and stable at pH within the range of 6 to 8. The phage XooX1IDN has a genome size of approximately 39 kb, while phage XooX2IDN had a genome size 38 kb. Morphologically, both phages possessed the family of Myoviridae. Phage biocontrol in vitro assay showed that both phages significantly reduced the growth of BLB pathogen, indicating that both phages potentially, as biological control agents for BLB disease in rice. © 2021 Friends Science Publishers

Response of rice genotypes to bacterial leaf streak caused by Xanthomonas oryzae pv. oryzicola, an emerging threat in Nepal.

Response of rice genotypes to bacterial leaf streak caused by Xanthomonas oryzae pv. oryzicola, an emerging threat in Nepal.

Antimicrobial activity of Streptomyces spp. isolated from Apis dorsata combs against some phytopathogenic bacteria.

The aim of this study was to investigate the antimicrobial potential of actinomycetes isolated from combs of the giant honey bee, Apis dorsata. In total, 25 isolates were obtained from three different media and were screened for antimicrobial activity against four plant pathogenic bacteria (Ralstonia solanacearum, Xanthomonas campestris pv. campestris, Xanthomonas oryzae pv. oryzae and Pectobacterium carotovorum). Following screening using a cross-streaking method, three isolates showed the potential to inhibit the growth of plant pathogenic bacteria. Based on a 96-well microtiter assay, the crude extract of DSC3-6 had minimum inhibitory concentration (MIC) values against X. oryzae pv. oryzae, X. campestris pv. campestris, R. solanacearum and P. carotovorum of 16, 32, 32 and 64 mg L−1, respectively. The crude extract of DGA3-20 had MIC values against X. oryzae pv. oryzae, X. campestris pv. campestris, R. solanacearum and P. carotovorum of 32, 32, 32 and 64 mg L−1, respectively. The crude extract of DGA8-3 at 32 mgL−1 inhibited the growth of X. oryzae pv. oryzae, X. campestris pv. campestris, R. solanacearum and P. carotovorum. Based on their 16S rRNA gene sequences, all isolates were identified as members of the genus Streptomyces. The analysis of 16S rRNA gene sequence similarity and of the phylogenetic tree based on the maximum likelihood algorithm showed that isolates DSC3-6, DGA3-20 and DGA8-3 were closely related to Streptomyces ramulosus (99.42%), Streptomyces axinellae (99.70%) and Streptomyces drozdowiczii (99.71%), respectively. This was the first report on antibacterial activity against phytopathogenic bacteria from actinomycetes isolated from the giant honey bee.

The Role of Nanochitosan on the Expression of Rice Resistance Genes against Bacterial Leaf Blight

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) has been reported to cause ± 20–50% of rice yield loss around the world. Resistant varieties are used to control this disease, however due to rapid evolution of this pathogen, the resistances was broken down in a few years. This study is aimed to determine the role of nanochitosan in the expression of rice Xa21 and Xa1 resistant genes against Xoo. The BLB susceptible rice cultivar IR64, the Xoo isolate MAG2 and a 0.065% concentration of nanochitosan were used in this experiment. Application of nanochitosan was carried out within 1-week intervals starting at rice aged 2–10 weeks after transplanting. The expression of Xa21 and Xa1 genes against Xoo were analyzed using conventional PCR and qPCR methods at 0 and 4 days after Xoo inoculation followed by 4x scoring of disease symptoms in 1-week interval. The treatments used in this study included the mock one/inoculated with sterile distilled water, K (+)/ plants inoculated with Xoo, CNP (-)/ with nanochitosan and sterile distilled water inoculation, and CNP (+)/ with nanochitosan and Xoo inoculation. The results showed that the 0.0065% concentration nanochitosan application was able to increase the expression of Xa21 and Xa1 genes on CNP (-). Disease intensity and AUDPC values did not show any significant difference between K (+) and CNP (+). This study concluded that nanochitosan at 0.065% was able to increase the expression of rice Xa21 and Xa1 resistance genes. However, the gene expression was not able to significantly suppress the infection development of Xoo.

Comparative proteomic analysis reveals novel insights into the interaction between rice and Xanthomonas oryzae pv. oryzae

BackgroundBacterial blight, which is caused by Xanthomonas oryzae pv. oryzae (Xoo), is a devastating rice disease worldwide. Rice introgression line H471, derived from the recurrent parent Huang-Hua-Zhan (HHZ) and the donor parent PSBRC28, exhibits broad-spectrum resistance to Xoo, including to the highly virulent Xoo strain PXO99A, whereas its parents are susceptible to PXO99A. To characterize the responses to Xoo, we compared the proteome profiles of the host and pathogen in the incompatible interaction (H471 inoculated with PXO99A) and the compatible interaction (HHZ inoculated with PXO99A).ResultsIn this study, a total of 374 rice differentially abundant proteins (DAPs) and 117 Xoo DAPs were detected in the comparison between H471 + PXO99A and HHZ + PXO99A. Most of the Xoo DAPs related to pathogen virulence, including the outer member proteins, type III secretion system proteins, TonB-dependent receptors, and transcription activator-like effectors, were less abundant in the incompatible interaction than in the compatible interaction. The rice DAPs were mainly involved in secondary metabolic processes, including phenylalanine metabolism and the biosynthesis of flavonoids and phenylpropanoids. Additionally, some DAPs involved in the phenolic phytoalexin and salicylic acid (SA) biosynthetic pathways accumulated much more in H471 than in HHZ after the inoculation with PXO99A, suggesting that phytoalexin and SA productions were induced faster in H471 than in HHZ. Further analyses revealed that the SA content increased much more rapidly in H471 than in HHZ after the inoculation, suggesting that the SA signaling pathway was activated faster in the incompatible interaction than in the compatible interaction.ConclusionsOverall, our results indicate that during an incompatible interaction between H471 and PXO99A, rice plants prevent pathogen invasion and also initiate multi-component defense responses that inhibit disease development.

Study of Biochemical and Molecular Changes of Iranian Rice Cultivars in Interaction with Bacterial Pathogen Xanthomonas oryzae pv. oryzae Causes Leaf Blight Disease

Study of Biochemical and Molecular Changes of Iranian Rice Cultivars in Interaction with Bacterial Pathogen Xanthomonas oryzae pv. oryzae Causes Leaf Blight Disease

Genome-Wide Association Analysis Identifies Resistance Loci for Bacterial Leaf Streak Resistance in Rice (Oryza sativa L.).

Bacterial leaf streak (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc) is one of the most devastating diseases in rice production areas, especially in humid tropical and subtropical zones throughout Asia and worldwide. A genome-wide association study (GWAS) analysis conducted on a collection of 236 diverse rice accessions, mainly indica varieties, identified 12 quantitative trait loci (QTLs) on chromosomes 1, 2, 3, 4, 5, 8, 9 and 11, conferring resistance to five representative isolates of Thai Xoc. Of these, five QTLs conferred resistance to more than one Xoc isolates. Two QTLs, qBLS5.1 and qBLS2.3, were considered promising QTLs for broad-spectrum resistance to BLS. The xa5 gene was proposed as a potential candidate gene for qBLS5.1 and three genes, encoding pectinesterase inhibitor (OsPEI), eukaryotic zinc-binding protein (OsRAR1), and NDP epimerase function, were proposed as candidate genes for qBLS2.3. Results from this study provide an insight into the potential QTLs and candidate genes for BLS resistance in rice. The recessive xa5 gene is suggested as a potential candidate for strong influence on broad-spectrum resistance and as a focal target in rice breeding programs for BLS resistance.

Pathogen-Induced Expression of OsDHODH1 Suggests Positive Regulation of Basal Defense Against Xanthomonas oryzae pv. oryzae in Rice

Bacterial leaf blight (BLB), a vascular disease caused by Xanthomonasoryzae pv. oryzae (Xoo), induces a significant reduction in rice yield in severe epidemics. This study investigated the transcriptional regulation of the OsDHODH1 gene in rice cultivars exposed to the Xoo K3 isolate. The symptoms were monitored on a daily basis, and the lesion length of inoculated rice plants was scored 21 days post inoculation (dpi). The most resistant and the highly susceptible cultivars were used for gene expression analysis. The dihydroorotate dehydrogenase (DHODH) domain is shared by many proteins in different plant species, and in Arabidopsis, this protein is encoded by the AtPYD1 gene. To investigate the functional role of the OsDHODH1 gene under bacterial infection, we inoculated the Arabidopsispyd1-2 knockout (atpyd1-2) plants, lacking the AtPYD1 gene (orthologous gene of the rice OsDHODH1), with Pseudomonassyringae pv. tomato (Pst) DC3000 vir, and the phenotypic response was scored 9 dpi. Results show that OsDHODH1 was upregulated in Tunnae, the most resistant rice cultivar but downregulated in IRAT112, the highly susceptible rice cultivar. In addition, Tunnae, Sipi and NERICA-L14 exhibited a durable resistance phenotype towards Xoo K3 isolate 21 dpi. Moreover, the expression of OsPR1a and OsPR10b (the rice pathogenesis inducible genes) was significantly upregulated in Tunnae, while being suppressed in IRAT112. Furthermore, the atpyd1-2 plants exhibited a high susceptibility towards Pst DC3000 vir. AtPR1 and AtPR2 (the Arabidopsis pathogenesis inducible genes) transcripts decreased in the atpyd1-2 plants compared to Col-0 (wild type) plants. Due to the above, OsDHODH1 and AtPYD1 are suggested to be involved in the basal adaptive response mechanisms towards bacterial pathogen resistance in plants.

Design, synthesis, and biological activity of novel 1,2,4-oxadiazole derivatives

BackgroundPlant diseases seriously threaten food security, it is urgent to discover efficient and low-risk chemical pesticides. 1,2,4-Oxadiazole derivatives exhibit broad spectrum of agricultural biological activities. For discovering novel molecules with excellent agricultural activities, novel 1,2,4-oxadiazole derivatives were synthesized and evaluated for their agricultural activities.ResultBioassays results showed that the title compounds exhibited moderate nematocidal activity against Meloidogyne incognita and anti-fungal activity to Rhizoctonia solani. It’s worth noting that compounds 5m, 5r, 5u, 5v, 5x and 5y showed strong antibacterial effects on Xanthomonas oryzae pv. oryzae (Xoo), with EC50 values of 36.25, 24.14, 28.82, 19.44, 25.37 and 28.52 μg/mL, respectively, superior to bismerthiazol (BMT, EC50 = 77.46 μg/mL) and thiodiazole copper (TDC, EC50 = 99.31 μg/mL). Compounds 5p, 5u and 5v exhibited excellent antibacterial ability against Xanthomonas oryzae pv. oryzicola (Xoc), with EC50 values of 31.40, 19.04 and 21.78 μg/mL, respectively, better than that of BMT (EC50 = 68.50 μg/mL) and TDC (EC50 = 91.05 μg/mL). In addition, compound 5v exerted moderate antibacterial effects on rice bacterial leaf blight.ConclusionsTwenty-six novel 1,2,4-oxadiazole derivatives were obtained and their biological activities were evaluated. Compound 5u and 5v exhibited excellent antibacterial activity Xoo and Xoc. These results indicated that 1,2,4-oxadiazole derivatives containing a trifluoromethyl pyridine moiety could be as potential alternative templates for discovering novel antibacterial agents.

Synergistic consortium of beneficial microorganisms in rice rhizosphere promotes host defense to blight-causing Xanthomonas oryzae pv. oryzae.

Rice plants primed with beneficial microbes Bacillus amyloliquefaciens and Aspergillus spinulosporus with biocontrol potential against Xanthomonas oryzae pv. oryzae, provided protection from disease by reprogramming host defence response under pathogen challenge. Plant-beneficial microbe interactions taking place in the rhizosphere are widely used for growth promotion and mitigation of biotic stresses in plants. The present study aims to evaluate the defense network induced by beneficial microorganisms in the rice rhizosphere, and the three-way interaction involved upon inoculation with dreadful bacteria Xanthomonas oryzae pv. oryzae (Xoo). Differential expression of defense-related enzymes, proteins, and genes in rice variety Swarna primed with a microbial consortium of Bacillus amyloliquefaciens and Aspergillus spinulosporus were quantified in the presence and absence of Xoo. The time-based expression profile alterations in leaves under the five distinct treatments "(unprimed unchallenged, unprimed Xoo challenged, B. amyloliquefaciens primed and challenged, A. spinulosporus primed and challenged, B. amyloliquefaciens and A. spinulosporus consortium primed and challenged)" revealed differential early upregulation of SOD, PAL, PO, PPO activities and TPC content in beneficial microbes primed plants in comparison to unprimed challenged plants. The enhanced defense response in all the rice plants recruited with beneficial microbe was also reflected by reduced plant mortality and an increased plant dry biomass and chlorophyll content. Also, more than 550 protein spots were observed per gel by PD Quest software, a total of 55 differentially expressed protein spots were analysed used MALDI-TOF MS, out of which 48 spots were recognized with a significant score with direct or supporting roles in stress alleviation and disease resistance. qRT-PCR was carried out to compare the biochemical and proteomic data to mRNA levels. We conclude that protein biogenesis and alleviated resistance response may contribute to improved biotic stress adaptation. These results might accelerate the functional regulation of the Xoo-receptive proteins in the presence of beneficial rhizospheric microbes and their computation as promising molecular markers for superior disease management.

Comparative microRNA profiling reveals microRNAs involved in rice resistant response to bacterial blight

Bacterial blight (BB), which is caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the most destructive bacterial diseases of rice (Oryza sativa L.). During plant defense responses, microRNAs (miRNAs) play important roles in regulating disease resistance. However, the functions of miRNAs in the interaction between rice and Xoo remain relatively uncharacterized. In this study, we compared the miRNA profiles of the BB resistant rice introgression line F329 and its susceptible recurrent parent Huang-Hua-Zhan (HHZ) at multiple time points after inoculation with Xoo. A total of 538 known and 312 novel miRNAs were identified, among which only 17 and 26 were responsive to Xoo infection in F329 and HHZ, respectively. Compared with the expression levels in HHZ, 37 up-regulated and 53 down-regulated miRNAs were detected in F329. The predicted target genes for the miRNAs differentially expressed between F329 and HHZ were revealed to be associated with flavonoid synthesis, the reactive oxygen species regulatory pathway, plant hormone signal transduction, defense responses, and growth and development. Additionally, the patterns of interactions between osa-miR390-3p, novel_miR_104, novel_miR_238, osa-miR166k-5p, osa-miR529b, and osa-miR167h-3p and their target genes were further validated by quantitative real-time PCR. Furthermore, we overexpressed osa-miR167h-3p in transgenic plants and proved that this miRNA positively regulates the resistance of rice to BB. These results provide novel information regarding the miRNA-based molecular mechanisms underlying the disease resistance of rice. The data presented herein may be useful for engineering rice BB resistance via miRNAs.

Two nuclear effectors of the rice blast fungus modulate host immunity via transcriptional reprogramming

Pathogens utilize multiple types of effectors to modulate plant immunity. Although many apoplastic and cytoplasmic effectors have been reported, nuclear effectors have not been well characterized in fungal pathogens. Here, we characterize two nuclear effectors of the rice blast pathogen Magnaporthe oryzae. Both nuclear effectors are secreted via the biotrophic interfacial complex, translocated into the nuclei of initially penetrated and surrounding cells, and reprogram the expression of immunity-associated genes by binding on effector binding elements in rice. Their expression in transgenic rice causes ambivalent immunity: increased susceptibility to M. oryzae and Xanthomonas oryzae pv. oryzae, hemibiotrophic pathogens, but enhanced resistance to Cochliobolus miyabeanus, a necrotrophic pathogen. Our findings help remedy a significant knowledge deficiency in the mechanism of M. oryzae–rice interactions and underscore how effector-mediated manipulation of plant immunity by one pathogen may also affect the disease severity by other pathogens.

Improved photosystem II and defense enzymes activity in rice (Oryza sativa) by biopriming against Xanthomonas oryzae pv. oryzae.

Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major threat to rice production as it accounts for loss up to 50% of annual rice grain yield. Xoo causes leaf tissue necrosis and as a result there is downregulation of the photosynthetic mechanisms of plant. Measurement of chl a fluorescence is an easy, fast, non-invasive and highly sensitive technique that can be used to understand plant health by measuring alterations in PSII activity, in response to different biotic and abiotic stresses. In the present investigation, rice seeds were bio-primed with two bacterial spp. (e.g. Bacillus subtilis and B. megaterium) and one fungal strain (i.e. Trichoderma erinaceum). The induction of defence against BB disease by bio-priming with biotic agents, was studied as response in alteration of PSII and defence enzymes activity. Field experiment was conducted with the best biotic agent; i.e. B. subtilis obtained from all experiments to study whether defence induction by it have any side effect on rice yield and biomass. Net house and field experiments have suggested that among all the biotic agents studied, bio-priming of rice seeds with B. subtilis has protected the photosynthetic machinery of plants from being damaged by BB without having any detrimental effect on rice grain yield.

Transcriptome analysis of xa5-mediated resistance to bacterial leaf streak in rice (Oryza sativa L.)

Bacterial leaf steak (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc) is a devastating disease in rice production. The resistance to BLS in rice is a quantitatively inherited trait, of which the molecular mechanism is still unclear. It has been proved that xa5, a recessive bacterial blast resistance gene, is the most possible candidate gene of the QTL qBlsr5a for BLS resistance. To study the molecular mechanism of xa5 function in BLS resistance, we created transgenic lines with RNAi of Xa5 (LOC_Os05g01710) and used RNA-seq to analyze the transcriptomes of a Xa5-RNAi line and the wild-type line at 9 h after inoculation with Xoc, with the mock inoculation as control. We found that Xa5-RNAi could (1) increase the resistance to BLS as expected from xa5; (2) alter (mainly up-regulate) the expression of hundreds of genes, most of which were related to disease resistance; and (3) greatly enhance the response of thousands of genes to Xoc infection, especially of the genes involved in cell death pathways. The results suggest that xa5 is the cause of BLS-resistance of QTL qBlsr5a and it displays BLS resistance effect probably mainly because of the enhanced response of the cell death-related genes to Xoc infection.

Investigation on Data Fusion of Multisource Spectral Data for Rice Leaf Diseases Identification Using Machine Learning Methods.

Rice diseases are major threats to rice yield and quality. Rapid and accurate detection of rice diseases is of great importance for precise disease prevention and treatment. Various spectroscopic techniques have been used to detect plant diseases. To rapidly and accurately detect three different rice diseases [leaf blight (Xanthomonas oryzae pv. Oryzae), rice blast (Pyricularia oryzae), and rice sheath blight (Rhizoctonia solani)], three spectroscopic techniques were applied, including visible/near-infrared hyperspectral imaging (HSI) spectra, mid-infrared spectroscopy (MIR), and laser-induced breakdown spectroscopy (LIBS). Three different levels of data fusion (raw data fusion, feature fusion, and decision fusion) fusing three different types of spectral features were adopted to categorize the diseases of rice. Principal component analysis (PCA) and autoencoder (AE) were used to extract features. Identification models based on each technique and different fusion levels were built using support vector machine (SVM), logistic regression (LR), and convolution neural network (CNN) models. Models based on HSI performed better than those based on MIR and LIBS, with the accuracy over 93% for the test set based on PCA features of HSI spectra. The performance of rice disease identification varied with different levels of fusion. The results showed that feature fusion and decision fusion could enhance identification performance. The overall results illustrated that the three techniques could be used to identify rice diseases, and data fusion strategies have great potential to be used for rice disease detection.