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Conferring crops with resistance to multiple diseases is crucial for stable food production. Genetic engineering is an effective means of achieving this. The rice receptor-like cytoplasmic kinase BSR1 mediates microbe-associated molecular pattern-induced immunity. In our previous study, we demonstrated that rice lines overexpressing BSR1 under the control of the maize ubiquitin promoter exhibited broad-spectrum resistance to rice blast, brown spot, leaf blight, and bacterial seedling rot. However, unfavorable phenotypes were observed, such as a decreased seed germination rate and a partial darkening of husked rice. Herein, we present a strategy to address these unfavorable phenotypes using an OsUbi7 constitutive promoter with moderate expression levels and a pathogen-inducible PR1b promoter. Rice lines expressing BSR1 under the influence of both promoters maintained broad-spectrum disease resistance. The seed germination rate and coloration of husked rice were similar to those of the wild-type rice. [ABSTRACT FROM AUTHOR]

Abstract Necrotrophic pathogen Cochliobolus miyabeanus (C. miyabeanus) causes rice brown leaf spot disease and drastically affects the yield and quality of rice grains. However, the molecular mechanism of rice-C. miyabeanus remains poorly understood due to the limited research conducted on this pathosystem. To elucidate the molecular mechanism of rice-C. miyabeanus, a transcriptome analysis was conducted from in vitro and in planta grown C. miyabeanus. This analysis led to the identification of a total of 24,060 genes of which 426 in vitro and 57 in planta expressed genes were predicted to encode for secretory proteins. As these 57 genes were specifically expressed in planta and were predicted to be secretory in nature, these were consider as putative effectors, highlighting their possible roles in the fungal pathogenicity. Notably, among these putative effectors, CmXyn1 which encodes a glycosyl hydrolase 11 displayed the highest expression level under in planta conditions and was thus selected for further functional characterization. Interestingly, the extracellular expression of CmXyn1 transiently induced cell death in Nicotiana benthamiana leaves, while intracellular expression was comparatively lesser effective. In addition, transcriptome analysis on rice leaves during C. miyabeanus infection and comparing it to the rice leaf transcriptome data obtained during hemibiotrophic pathogen Magnaporthe oryzae infection led to the discovery of 18 receptors/receptor-like kinases that were commonly expressed in response to both pathogens, indicating their key roles in rice defense response. Taken together, our findings provide new insights into rice-C. miyabeanus interaction as well as the unique and common defense responses of rice against hemibiotroph and necrotroph model systems.

Necrotrophic pathogen Cochliobolus miyabeanus (C. miyabeanus) causes rice brown leaf spot disease and drastically affects the yield and quality of rice grains. However, the molecular mechanism of rice-C. miyabeanus remains poorly understood due to the limited research conducted on this pathosystem. To elucidate the molecular mechanism of rice-C. miyabeanus, a transcriptome analysis was conducted from in vitro and in planta grown C. miyabeanus. This analysis led to the identification of a total of 24,060 genes of which 426 in vitro and 57 in planta expressed genes were predicted to encode for secretory proteins. As these 57 genes were specifically expressed in planta and were predicted to be secretory in nature, these were consider as putative effectors, highlighting their possible roles in the fungal pathogenicity. Notably, among these putative effectors, CmXyn1 which encodes a glycosyl hydrolase 11 displayed the highest expression level under in planta conditions and was thus selected for further functional characterization. Interestingly, the extracellular expression of CmXyn1 transiently induced cell death in Nicotiana benthamiana leaves, while intracellular expression was comparatively lesser effective. In addition, transcriptome analysis on rice leaves during C. miyabeanus infection and comparing it to the rice leaf transcriptome data obtained during hemibiotrophic pathogen Magnaporthe oryzae infection led to the discovery of 18 receptors/receptor-like kinases that were commonly expressed in response to both pathogens, indicating their key roles in rice defense response. Taken together, our findings provide new insights into rice-C. miyabeanus interaction as well as the unique and common defense responses of rice against hemibiotroph and necrotroph model systems. [ABSTRACT FROM AUTHOR]

Brown spot disease in rice is caused by Cochliobolus miyabeanus (Anamorph: Bipolaris oryzae (Breda de Haan) Shoemaker, 1959 (Synonyms: Helminthosporium oryzae). It causes significant losses by affecting both economic yield and grain quality. Though, it is a minor disease in most of the parts of the world but the historical famines like Krishna Godaveri Delta famine and Bengal famines and huge crop losses in a number of incidences as in Guyana and Nigeria renders it as a potential threat to rice crop and adverted the requirement of efficient, sustainable and economical strategies to cope with the pathogen. In this context, availability of resistant sources against the pathogen is a noteworthy alternative for disease management. Realising the importance of resistant sources, the present research investigation was undertaken to study association between resistance to brown spot disease and yield attributing traits in rice via correlation studies and path analysis to identify high yielding resistant lines for brown spot disease in rice. In this study disease resistance expressed in terms of AUDPC showed negative correlation with yield and yield attributing traits and direct negative effect on yield. Thus, AUDPC can be utilised as a selection parameter for developing improved cultivars with higher grain yield and lower susceptibility towards the brown spot pathogen. [ABSTRACT FROM AUTHOR]

SUMMARY: The fungal genus Cochliobolus describes necrotrophic pathogens that give rise to significant losses on rice, wheat, and maize. Revealing plant mechanisms of non‐host resistance (NHR) against Cochliobolus will help to uncover strategies that can be exploited in engineered cereals. Therefore, we developed a heterogeneous pathosystem and studied the ability of Cochliobolus to infect dicotyledons. We report here that C. miyabeanus and C. heterostrophus infect Arabidopsis accessions and produce functional conidia, thereby demonstrating the ability to accept Brassica spp. as host plants. Some ecotypes exhibited a high susceptibility, whereas others hindered the necrotrophic disease progression of the Cochliobolus strains. Natural variation in NHR among the tested Arabidopsis accessions can advance the identification of genetic loci that prime the plant's defence repertoire. We found that applied phytotoxin‐containing conidial fluid extracts of C. miyabeanus caused necrotic lesions on rice leaves but provoked only minor irritations on Arabidopsis. This result implies that C. miyabeanus phytotoxins are insufficiently adapted to promote dicot colonization, which corresponds to a retarded infection progression. Previous studies on rice demonstrated that ethylene (ET) promotes C. miyabeanus infection, whereas salicylic acid (SA) and jasmonic acid (JA) exert a minor function. However, in Arabidopsis, we revealed that the genetic disruption of the ET and JA signalling pathways compromises basal resistance against Cochliobolus, whereas SA biosynthesis mutants showed a reduced susceptibility. Our results refer to the synergistic action of ET/JA and indicate distinct defence systems between Arabidopsis and rice to confine Cochliobolus propagation. Moreover, this heterogeneous pathosystem may help to reveal mechanisms of NHR and associated defensive genes against Cochliobolus infection. Significance Statement: Revealing plant mechanisms of non‐host resistance (NHR) against Cochliobolus will help to uncover strategies that can be exploited in engineered cereals. Thus, we developed a heterogeneous pathosystem and studied the ability of Cochliobolus to infect various Arabidopsis accessions. Our results indicate distinct defence systems between Arabidopsis and rice to confine Cochliobolus propagation. Moreover, this pathosystem may help to reveal mechanisms of NHR and associated defensive genes against Cochliobolus infection. [ABSTRACT FROM AUTHOR]

The leaf anatomy, photosynthetic system parameters and accumulation of carbohydrates were determined at different times for Bipolaris oryzae pathogenesis in two rice cultivars (BRS Querência and Inov CL), grown in an environment with 400 ppm or 700 ppm of atmospheric CO2. The results demonstrated that the plants exposed to 700 ppm underwent changes in anatomical characteristics (reduction in parenchyma thickness and size of bulliform cells), photosynthetic parameters (increased carbon assimilation rate, leaf intercellular CO2 concentration and water use efficiency, and reduction of stomatal conductance to water vapor, transpiration rate and carboxylation efficiency), and carbohydrate accumulation (increased concentration of soluble sugars and starch), when compared to plants at 400 ppm. Therefore, the changes in morphological traits of the leaf and the accumulation of carbohydrates, which were stimulated in the rice plants by increased CO2 concentration (700 ppm), were associated with less severe brown spot, caused by B. oryzae. [ABSTRACT FROM AUTHOR]

Cochliobolus miyabeanus is known as a significant causal agent in relation to brown spot disease of rice and causes significant yield losses. In the present study, the complete mitochondrial genome was determined using next-generation sequencing technology. This complete mitogenome is a circular molecule of 124,887 bp in length. It contains 13 conserved protein-coding genes, 21 transfer RNA genes, 2 ribosomal RNA genes and 9 open reading frames. The overall base composition of C. miyabeanus is 35.4% A, 34.4% T, 14.4% C, 15.8% G, with a CG content of 30.2%. Phylogenetic analysis based on concatenated protein genes from 15 taxa within Pezizomycotina showed that C. miyabeanus is closely related to Bipolaris cookei in the family Pleosporaceae (Dothideomycetes, Pleosporales). This work would facilitate the understanding of systematics and evolutionary biology of phytopathogenic fungi.

Bipolaris oryzae causes brown spot in rice ( Oryza sativa) inflicting substantial grain yield losses worldwide. Knowledge of the population structure, genetic diversity and sexual recombination of the fungal pathogen can help to implement effective disease management strategies. In this study, B. oryzae isolates sampled from Iran, the Philippines and Japan were analysed with 12 simple-sequence repeat ( SSR) markers, newly developed from the genome sequence of the fungus. Among the 288 B. oryzae isolates genotyped, 278 unique haplotypes were identified. High genotype numbers (richness) with even distribution (evenness) were found within the collection sites. Both mating types, MAT1-1 and MAT1-2, were present in each collection area, and the sexual state was induced under controlled conditions with production of viable ascospores. However, the tests of linkage disequilibrium rejected of the hypothesis of random mating. Discriminant analysis of principal components ( DAPC) revealed that the B. oryzae collection formed three clusters, each consisting of isolates from different collection sites. Analysis of molecular variance ( amova) showed that genetic variation among clusters was 18.7%, with the rest of the variation distributed within clusters ( RST = 0.187, P < 0.001). Statistically significant pairwise genetic differentiation was found between the clusters. These results show that Asian B. oryzae isolates are genetically diverse, and, overall, distributed in three groups. These findings will be helpful in managing the disease and guide the use of representative isolates needed for selection of resistant rice varieties. [ABSTRACT FROM AUTHOR]

Key message: The Pseudomonas- derived cyclic lipopeptide orfamide can induce resistance to Cochliobolus miyabeanus but not to Magnaporthe oryzae in rice. Abscisic acid signaling is involved in the induced systemic resistance response triggered by orfamide. Abstract: Diverse natural products produced by beneficial Pseudomonas species have the potential to trigger induced systemic resistance (ISR) in plants, and thus may contribute to control of diseases in crops. Some beneficial Pseudomonas spp. can produce cyclic lipopeptides (CLPs), amphiphilic molecules composed of a fatty acid tail linked to an oligopeptide which is cyclized. CLPs can have versatile biological functions, but the capacity of Pseudomonas-derived CLPs in triggering ISR responses has barely been studied. Pseudomonas protegens and related species can produce orfamide-type CLPs. Here we show that in rice, orfamides can act as ISR elicitors against the necrotrophic fungus Cochliobolus miyabeanus, the causal agent of brown spot disease, but are not active against the blast fungus Magnaporthe oryzae. Orfamide A can trigger early defensive events and activate transcripts of defense-related genes in rice cell suspension cultures, but does not cause cell death. Further testing in rice cell suspension cultures and rice plants showed that abscisic acid signaling, the transcriptional activator OsWRKY4 and pathogenesis-related protein PR1b are triggered by orfamide A and may play a role in the ISR response against C. miyabeanus. [ABSTRACT FROM AUTHOR]

Brown spot disease, caused by C ochliobolus miyabeanus, is currently considered to be one of the most important yield reducers of rice ( O ryza sativa L.). Despite its agricultural importance, little is known about the virulence mechanisms deployed by the fungus. Therefore, we set out to identify novel virulence factors with a role in disease development. This article reports, for the first time, the production of tentoxin by C . miyabeanus as a virulence factor during brown spot disease and the identification of the non-ribosomal protein synthetase ( NRPS) CmNps3, responsible for tentoxin biosynthesis. We compared the chemical compounds produced by C . miyabeanus strains differing in virulence ability using ultra-high-performance liquid chromatography ( UHPLC) coupled to high-resolution Orbitrap mass spectrometry ( HRMS). The production of tentoxin by a highly virulent strain was revealed by principal component analysis of the detected ions and confirmed by UHPLC coupled to tandem-quadrupole mass spectrometry ( MS/ MS). The corresponding NRPS was identified by in silico genome analysis and confirmed by gene deletion. Infection tests with wild-type and C mnps3 mutants showed that tentoxin acts as a virulence factor and is correlated with chlorosis development during the second phase of infection. Although rice has previously been classified as a tentoxin-insensitive plant species, our data demonstrate that tentoxin production by C . miyabeanus affects symptom development. [ABSTRACT FROM AUTHOR]

Broad-spectrum disease resistance against two or more types of pathogen species is desirable for crop improvement. In rice, Xanthomonas oryzae pv. oryzae (Xoo), the causal bacteria of rice leaf blight, and Magnaporthe oryzae, the fungal pathogen causing rice blast, are two of the most devastating pathogens. We identified the rice BROAD-SPECTRUM RESISTANCE 1 (BSR1) gene for a BIK1-like receptor-like cytoplasmic kinase using the FOX hunting system, and demonstrated that BSR1-overexpressing (OX) rice showed strong resistance to the bacterial pathogen, Xoo and the fungal pathogen, M. oryzae. Here, we report that BSR1-OX rice showed extended resistance against two other different races of Xoo, and to at least one other race of M. oryzae. In addition, the rice showed resistance to another bacterial species, Burkholderia glumae, which causes bacterial seedling rot and bacterial grain rot, and to Cochliobolus miyabeanus, another fungal species causing brown spot. Furthermore, BSR1-OX rice showed slight resistance to rice stripe disease, a major viral disease caused by rice stripe virus. Thus, we demonstrated that BSR1-OX rice shows remarkable broad-spectrum resistance to at least two major bacterial species and two major fungal species, and slight resistance to one viral pathogen. [ABSTRACT FROM AUTHOR]

Although numerous studies have shown the ability of silicon (Si) to mitigate a wide variety of abiotic and biotic stresses, relatively little is known about the underlying mechanism(s). Here, we have investigated the role of hormone defense pathways in Si-induced resistance to the rice brown spot fungus Cochliobolus miyabeanus., To delineate the involvement of multiple hormone pathways, a multidisciplinary approach was pursued, combining exogenous hormone applications, pharmacological inhibitor experiments, time-resolved hormone measurements, and bioassays with hormone-deficient and/or -insensitive mutant lines., Contrary to other types of induced resistance, we found Si-induced brown spot resistance to function independently of the classic immune hormones salicylic acid and jasmonic acid. Our data also rule out a major role of the abscisic acid (ABA) and cytokinin pathways, but suggest that Si mounts resistance to C. miyabeanus by preventing the fungus from hijacking the rice ethylene ( ET) machinery. Interestingly, rather than suppressing rice ET signaling per se, Si probably interferes with the production and/or action of fungal ET., Together our findings favor a scenario whereby Si induces brown spot resistance by disarming fungal ET and argue that impairment of pathogen virulence factors is a core resistance mechanism underpinning Si-induced plant immunity. [ABSTRACT FROM AUTHOR]

Much has been written and said of the importance of crop management to sustain plant health, a fundamental for feeding a world population expected to reach around nine billion by 2050. Yet, the two elements, crop management and plant health management, are generally addressed as two distinct entities, the former often being seen as a source for options for the latter. Agriculture of the Middle Age (900-1600 CE) seems not always to have distinguished crop and plant health management, considering them instead as a whole. In this article, these elements are addressed as parts of production situations, which represent a much broader level of integration for systems analysis. At the production situation level, plant disease epidemics, or their suppression, can both be seen as consequences of crop management. Modern agriculture tends to distinguish specific plant health management techniques (which are often over-emphasized) and general, non-specific ones (which are often downplayed). The former (e.g., specific host plant resistances, biological control, pesticides) may be overcome rather rapidly by plant pathogens, while the latter (e.g., crop rotation, tillage), with often progressive, incomplete, and confounded effects, may constitute the basis of sustainable management of plant health. A simulation modelling framework, with two model structures, is used to highlight the three components of disease management outlined by Berger ( Annual Review of Phytopathology, 15, 165-183, ): (1) eliminate or reduce the initial inoculum or delay its appearance, (2) slow the rate of disease increase, and (3) shorten the time of exposure of the crop to the pathogen. The degree of involvement of these three components is further discussed in three groups of examples in plant production systems that significantly contribute to global food provisioning and food security. A few modelling outputs and evaluation of these examples suggest that, even in the most specialized production situations, both specific and non-specific plant health management strategies are necessary for sustained health of our crops and for durable performances of agricultural systems. [ABSTRACT FROM AUTHOR]

Five rice cultivars, one hybrid (WR96), three modern (BR16, BR26, and BRRI Dhan27) and one local (Pari) were screened for reaction to brown leaf spot disease caused byCochliobolus miyabeanusand performance of yield-related characters. The severity of brown leaf spot varied with growth stages of rice plant as well as different cultivars tested under field condition. Low disease severity was observed at maximum tillering stage compared to moderate to high at dough stage, with hybrid cultivar WR96 showing highest disease, while local cultivar Pari had the lowest. Brown spot disease severity in different cultivars under induced epiphytic condition also followed the similar trend. The results also revealed that most of the yield-contributing characters examined showed wide variations among the cultivars. Modern cultivar BR16 produced the highest panicle length, number of grain per panicle and grain yield per hectare. At the same time as local cultivar Pari generated the lowest number of tiller per plant, panicle length, grain number per panicle and grain yield per hectare. Moreover, hybrid cultivar WR96 produced the highest percentage of spotted grain per panicle and seed yieldingC. miyabeanus, and also the lower percentage of seed germination, while the reverse was observed in local cultivar Pari. These findings may allow producers and breeders to select rice cultivar, resistant or tolerant to brown leaf spot disease and to avoid significant reductions in grain yields. [ABSTRACT FROM AUTHOR]

The effects of essential oils (EO), cold water (CWE), hot water (HWE) and ethanol (ETHE) extracts of Callistemon citrinus L. and Cymbopogon citratus (DC) Stapf on the radial growth of Alternaria padwickii (Ganguly) M.B. Ellis and Bipolaris oryzae (Breda de Haan) Shoemaker, the control of brown spot disease, the tillering, the number of panicles and the yield increase in rice were evaluated under laboratory and field conditions. In vitro, the growth of both fungi was completely inhibited by the EO of C. citrinus and C. citratus at 4,520 μg/ml and 452 μg/ml, respectively. For solvent extracts, the ETHE of C. citrinus was the most active and inhibited 80-85 % of the fungal growth followed by the CWE of C. citratus with 77 % and 36 % diameter reduction against B. oryzae and A. padwickii, respectively at 10 000 μg/ml. Under laboratory conditions, seed treatment with the EO of C. citrinus reduced the incidence of B. oryzae in seeds by 85-100 % compared to the non-treated controls. Similarly, the seed treatment increased the germination of an irrigated rice cultivar by 10.6 %, whereas the percentage of germinated seeds of upland rice was not significantly affected. The highest germination (85-94 %) was found in the non-treated and treated samples with a low incidence (0-4 %) of B. oryzae. Under field conditions, the combined use of the essential oil of C. citrinus as a seed treatment and spraying the plants with 2 % ethanol followed by 2 % (w/v) aqueous extracts of C. citrinus or C. citratus increased the emergence, tillering, panicles/plant and the grain yield by 25-55 % of the irrigated rice. In addition, the brown spot severity was reduced by 36-42 %. For the upland rice, the treatments led to similar results with the grain yield increase of 54-137 % and 20-80 % reduction in the brown spot severity. From our results, we concluded that the EO and solvent extracts of C. citrinus and C. citratus have potential as control agents against brown spot and other seed-borne fungal diseases in rice under both conventional and organic farming. [ABSTRACT FROM AUTHOR]

The genotypic diversity of a collection of 352 isolates of Bipolaris oryzae obtained from 11 locations in the Philippines was estimated. The isolates could be divided into 50 haplotypes based on variation in microsatellite DNA with a moderately high genotypic diversity value of 0.88. Thirty nine haplotypes were represented by three or fewer isolates, whereas 80 % of the isolates belonged to only eight haplotypes, each containing 10 to 88 isolates indicating the prevalence of clonality. AMOVA revealed that the greatest variation was associated with the brown spot isolates collected within provinces (50.81 %), among varieties within provinces (48.17 %) and within ecosystems (49.33 %). Intensive sampling from a single field showed that the population was mostly clonal with about 98 % of the isolates belonging to a single VNTR haplotype. However, isolates within this haplotype exhibited a continuous range of aggressiveness when inoculated onto susceptible rice variety IR72. Several types of lesions were observed in the field during sampling, but the isolates obtained from each type of lesion produced a range of different lesion types when inoculated onto leaves of IR72, indicating that the type of lesion observed in the field was not related to the genotype of the pathogen. These results show that rice fields across the Philippines may contain B. oryzae isolates with considerable genotypic diversity, but an individual field may have both clonal and unique genotypes. [ABSTRACT FROM AUTHOR]

Plants are constantly threatened by a wide array of microbial pathogens. Pathogen invasion can lead to vast yield losses and the demand for sustainable plant-protection strategies has never been greater. Chemical plant activators and selected strains of rhizobacteria can increase resistance against specific types of pathogens but these treatments are often ineffective or even cause susceptibility against others. Silicon application is one of the scarce examples of a treatment that effectively induces broad-spectrum disease resistance. The prophylactic effect of silicon is considered to be the result of both passive and active defences. Although the phenomenon has been known for decades, very little is known about the molecular basis of silicon-afforded disease control. By combining knowledge on how silicon interacts with cell metabolism in diatoms and plants, this review describes silicon-induced regulatory mechanisms that might account for broad-spectrum plant disease resistance. Priming of plant immune responses, alterations in phytohormone homeostasis, regulation of iron homeostasis, silicon-driven photorespiration and interaction with defence signalling components all are potential mechanisms involved in regulating silicon-triggered resistance responses. Further elucidating how silicon exerts its beneficial properties may create new avenues for developing plants that are better able to withstand multiple attackers. [ABSTRACT FROM AUTHOR]

A collection of 168 Cochliobolus miyabeanus isolates was made from cultivated wildrice ( Zizania palustris) paddies in Minnesota, USA, during 2007 and 2008. Analysis of 26 polymorphic amplified fragment length polymorphism (AFLP) markers generated with three primer-pair combinations indicated a moderate average gene diversity () of 0·283. Genotypic diversity was high in all collection areas with the exception of a paddy in Itasca County. Significant population subdivision by collection site was found with amova tests using both the entire fungal population data ( FST = 0·29, P < 0·001) and the clone-corrected data ( FST = 0·08, P < 0·001), and with a Markov chain Monte Carlo approach. Abundant immigrants, shared haplotypes and admixed genotypes were found in paddies in central-eastern areas. Although indirect tests did not support the hypothesis of random mating at the subpopulation level, sexual recombination nevertheless may be possible in areas where both mating type idiomorphs, MAT1-1 and MAT1-2, were found. These results may have implications in breeding for resistance and disease management. [ABSTRACT FROM AUTHOR]

Cochliobolus miyabeanus is known as a significant causal agent in relation to brown spot disease of rice and causes significant yield losses. In the present study, the complete mitochondrial genome was determined using next-generation sequencing technology. This complete mitogenome is a circular molecule of 124,887 bp in length. It contains 13 conserved protein-coding genes, 21 transfer RNA genes, 2 ribosomal RNA genes and 9 open reading frames. The overall base composition of C. miyabeanus is 35.4% A, 34.4% T, 14.4% C, 15.8% G, with a CG content of 30.2%. Phylogenetic analysis based on concatenated protein genes from 15 taxa within Pezizomycotina showed that C. miyabeanus is closely related to Bipolaris cookei in the family Pleosporaceae (Dothideomycetes, Pleosporales). This work would facilitate the understanding of systematics and evolutionary biology of phytopathogenic fungi. [ABSTRACT FROM AUTHOR]

A simulation study was conducted to assess the current and prospective efficiency of rice pest management and develop research priorities for lowland production situations in tropical Asia. Simulation modeling with the RICEPEST model provided the flexibility required to address varying production situations and diverse pest profiles (bacterial leaf blight, sheath blight, brown spot, leaf blast, neck blast, sheath rot, white heads, dead hearts, brown plant-hoppers, insect defoliators, and weeds). Operational definitions for management efficacy (injury reduction) and management efficiency (yield gain) were developed. This approach enabled the modeling of scenarios pertaining to different pest management strategies within the agroecological contexts of rice production and their associated pest injuries. Rice pests could be classified into two broad research priority-setting categories with respect to simulated yield losses and management efficiencies. One group, including weeds, sheath blight, and brown spot, consists of pests for which effective pest management tools need to be developed. The second group consists of leaf blast, neck blast, bacterial leaf blight, and brown plant-hoppers, for which the efficiency of current management methods is to be maintained. Simulated yield losses in future production situations indicated that a new type of rice plant with high-harvest index and high-biomass production ("New Plant Type") was more vulnerable to pests than hybrid rice. Simulations also indicated that the impact of deployment of host resistance (e.g., through genetic engineering) was much larger when targeted against sheath blight than when targeted against stem borers. Simulated yield losses for combinations of production situations and injury profiles that dominate current lowland rice production in tropical Asia ranged from 140 to 230 g m-2. For these combinations, the simulated efficiency of current pest management methods, expressed in terms of relative yield gains, ranged from 0.38 to 0.74. Overall, the analyses indicated that 120 to 200 × 106 tons of grain yield are lost yearly to pests over the 87 × 106 ha of lowland rice in tropical Asia. This also amounts to the potential gain that future pest management strategies could achieve, if deployed. [ABSTRACT FROM AUTHOR]

Rice plants cultivated under 700 ppm atmospheric CO 2 concentration presented a reduction in the progress and severity of the brown spot disease (Bipolaris oryzae), through the enhancement of biochemical defense mechanisms. Plants exposed to 700 ppm of CO 2 had higher activity of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, polyphenoloxidase and chitinase, and increased phenolic compounds and lignin concentration, independent of the rice cultivar. Therefore, the lower severity values of the disease were related to changes in the development of the lesions as a result of the defense responses, which were stimulated in the rice plants by the increase of CO 2 concentration. • This study demonstrated that increase of atmospheric CO 2 improves rice resistance to brown spot. • Rice under enhanced atmospheric CO 2 concentration have a better attenuation of the oxidative damages. • Rice under enhanced atmospheric CO 2 concentration have the reduction on the severity of the brown spot. • Rice exposed to 700 ppm of CO 2 had higher activity of antioxidant enzymes. • Rice exposed to 700 ppm of CO 2 had higher concentration of phenolic compounds and lignin content. [ABSTRACT FROM AUTHOR]

Cochliobolus miyabeanus is known as a significant causal agent in relation to brown spot disease of rice and causes significant yield losses. In the present study, the complete mitochondrial genome was determined using next-generation sequencing technology. This complete mitogenome is a circular molecule of 124,887 bp in length. It contains 13 conserved protein-coding genes, 21 transfer RNA genes, 2 ribosomal RNA genes and 9 open reading frames. The overall base composition of C. miyabeanus is 35.4% A, 34.4% T, 14.4% C, 15.8% G, with a CG content of 30.2%. Phylogenetic analysis based on concatenated protein genes from 15 taxa within Pezizomycotina showed that C. miyabeanus is closely related to Bipolaris cookei in the family Pleosporaceae (Dothideomycetes, Pleosporales). This work would facilitate the understanding of systematics and evolutionary biology of phytopathogenic fungi., Competing Interests: No potential conflict of interest was reported by the authors., (© 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)

Broad-spectrum disease resistance against two or more types of pathogen species is desirable for crop improvement. In rice, Xanthomonas oryzae pv. oryzae (Xoo), the causal bacteria of rice leaf blight, and Magnaporthe oryzae, the fungal pathogen causing rice blast, are two of the most devastating pathogens. We identified the rice BROAD-SPECTRUM RESISTANCE 1 (BSR1) gene for a BIK1-like receptor-like cytoplasmic kinase using the FOX hunting system, and demonstrated that BSR1-overexpressing (OX) rice showed strong resistance to the bacterial pathogen, Xoo and the fungal pathogen, M. oryzae. Here, we report that BSR1-OX rice showed extended resistance against two other different races of Xoo, and to at least one other race of M. oryzae. In addition, the rice showed resistance to another bacterial species, Burkholderia glumae, which causes bacterial seedling rot and bacterial grain rot, and to Cochliobolus miyabeanus, another fungal species causing brown spot. Furthermore, BSR1-OX rice showed slight resistance to rice stripe disease, a major viral disease caused by rice stripe virus. Thus, we demonstrated that BSR1-OX rice shows remarkable broad-spectrum resistance to at least two major bacterial species and two major fungal species, and slight resistance to one viral pathogen.

Necrotrophic fungal pathogen Cochliobolus miyabeanus causes brown spot disease in rice leaves upon infection, resulting in critical rice yield loss. To better understand the rice-C. miyabeanus interaction, we employed proteomic approaches to establish differential proteomes of total and secreted proteins from the inoculated leaves. The 2DE approach after PEG-fractionation of total proteins coupled with MS (MALDI-TOF/TOF and nESI-LC-MS/MS) analyses led to identification of 49 unique proteins out of 63 differential spots. SDS-PAGE in combination with nESI-LC-MS/MS shotgun approach was applied to identify secreted proteins in the leaf apoplast upon infection and resulted in cataloging of 501 unique proteins, of which 470 and 31 proteins were secreted from rice and C. miyabeanus, respectively. Proteins mapped onto metabolic pathways implied their reprogramming upon infection. The enzymes involved in Calvin cycle and glycolysis decreased in their protein abundance, whereas enzymes in the TCA cycle, amino acids, and ethylene biosynthesis increased. Differential proteomes also generated distribution of identified proteins in the intracellular and extracellular spaces, providing a better insight into defense responses of proteins in rice against C. miyabeanus. Established proteome of the rice-C. miyabeanus interaction serves not only as a good resource for the scientific community but also highlights its significance from biological aspects., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)