Rice Blast
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Scientific articles on rice blast and wheat blast 20 new articles each month !
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Marker‐assisted selection for rice blast resistance genes Pi2 and Pi9 through high‐resolution melting of a gene‐targeted amplicon

Marker‐assisted selection for rice blast resistance genes Pi2 and Pi9 through high‐resolution melting of a gene‐targeted amplicon | Rice Blast | Scoop.it
The use of host resistance (R) genes is considered the most cost-effective option to control the rice blast disease. The two allelic R genes Pi2 and Pi9 confer very broad-spectrum resistance against blast isolates collected worldwide. However, the two genes have not yet been widely deployed in rice breeding programmes. Availability of specific markers for them would facilitate incorporating the two R genes into new rice lines through marker-assisted selection. Herein, we report the development and utilization of a robust and specific marker for the Pi2 and Pi9. This marker was derived from polymorphisms within the target gene, and achieved simultaneously distinguish Pi2 and Pi9 from other alleles through high-resolution melting of a small amplicon. With the marker, we were able to transfer the Pi2 into an elite restorer line through marker-assisted backcrossing, successfully obtained effective resistance to blast disease, and we were also able to, respectively, incorporate the Pi2 and Pi9 with two other R genes. As the additive effect, blast resistance in these stacking lines harbouring three R genes were significantly improved.
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Enhanced resistance of PsbS-deficient rice (Oryza sativa L.) to fungal and bacterial pathogens

The 22-kDa PsbS protein of Photosystem II is involved in nonphotochemical quenching (NPQ) of chlorophyll fluorescence. Genome-wide analysis of the expression pattern in PsbS knockout (KO) rice plants showed that a lack of this protein led to changes in the transcript levels of 406 genes, presumably a result of superoxide produced in the chloroplasts. The top Gene Ontology categories, in which expression was the most differential, included ‘Immune response’, ‘Response to jasmonic acid’, and ‘MAPK cascade’. From those genes, we randomly selected nine that were up-regulated. Our microarray results were confirmed by quantitative RT-PCR analysis. The KO and PsbS RNAi (knockdown) plants were more resistant to pathogens Magnaporthe oryzae PO6-6 and Xanthomonas oryzae pv. oryzae than either the wild-type plants or PsbS-overexpressing transgenic line. These findings suggest that superoxide production might be the reason that these plants have greater pathogen resistance to fungal and bacterial pathogens in the absence of energy-dependent NPQ. For example, a high level of cell wall lignification in the KO mutants was possibly due to enhanced superoxide production. Our data indicate that certain abiotic stress-induced reactive oxygen species can promote specific signaling pathways, which then activate a defense mechanism against biotic stress in PsbS-KO rice plants
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PHI-base: a new interface and further additions for the multi-species pathogen–host interactions database

PHI-base: a new interface and further additions for the multi-species pathogen–host interactions database | Rice Blast | Scoop.it
The pathogen–host interactions database (PHI-base) is available at www.phi-base.org. PHI-base contains expertly curated molecular and biological information on genes proven to affect the outcome of pathogen–host interactions reported in peer reviewed research articles. In addition, literature that indicates specific gene alterations that did not affect the disease interaction phenotype are curated to provide complete datasets for comparative purposes. Viruses are not included. Here we describe a revised PHI-base Version 4 data platform with improved search, filtering and extended data display functions. A PHIB-BLAST search function is provided and a link to PHI-Canto, a tool for authors to directly curate their own published data into PHI-base. The new release of PHI-base Version 4.2 (October 2016) has an increased data content containing information from 2219 manually curated references. The data provide information on 4460 genes from 264 pathogens tested on 176 hosts in 8046 interactions. Prokaryotic and eukaryotic pathogens are represented in almost equal numbers. Host species belong ∼70% to plants and 30% to other species of medical and/or environmental importance. Additional data types included into PHI-base 4 are the direct targets of pathogen effector proteins in experimental and natural host organisms. The curation problems encountered and the future directions of the PHI-base project are briefly discussed.
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Rice varieties with resistance to multiple races of Magnaporthe oryzae offer opportunities to manage rice blast in Australia

Rice varieties with resistance to multiple races of Magnaporthe oryzae offer opportunities to manage rice blast in Australia | Rice Blast | Scoop.it
Rice blast caused by Magnaporthe oryzae is the most destructive disease of rice worldwide. Development of resistant varieties is considered as the most cost-effective and sustainable way to manage rice blast. However, there remains a lack of knowledge about the resistance of rice varieties to blast disease in Australia. This study was conducted to determine if there was any resistance existing among the rice varieties grown in Australia to M. oryzae isolates from this country that belong to different races. There was a resistant reaction of the variety SHZ-2 to all the five races of IA-1, IA-3, IA-63, IB-3 and IB-59, with a percent disease index (%DI) less than 40. Varieties NTR587, BR-IRGA-409, Ceysvoni and Rikuto Norin 20 showed a resistant reaction to races IA-3, IA-63, IB-3 and IB-59; and the variety Kyeema exhibited a resistant reaction to races IA-3, IB-3 and IB-59. For the races IA-1 and IB-59 with more than one isolate, varieties with differential disease reactions across different isolates belonging to the same race were also revealed: five varieties, Langi, Opus, Sherpa, Viet 1 and Topaz, exhibited differential disease reactions to the three IA-1 isolates; 10 varieties showed differential disease reactions to the four IB-59 isolates; in addition, the varieties that had differential disease reactions to the IA-1 isolates also exhibited differential disease reactions to the IB-59 isolates of race. This study provides valuable resistance sources for breeding programmes to develop rice varieties with resistance to multiple races of M. oryzae in Australia.
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Transcriptome Analysis Highlights Defense and Signaling Pathways Mediated by Rice pi21 Gene with Partial Resistance to Magnaporthe oryzae

Transcriptome Analysis Highlights Defense and Signaling Pathways Mediated by Rice pi21 Gene with Partial Resistance to Magnaporthe oryzae | Rice Blast | Scoop.it
Rice blast disease is one of the most destructive rice diseases worldwide. The pi21 gene confers partial and durable resistance to Magnaporthe oryzae. However, little is known regarding the molecular mechanisms of resistance mediated by the loss-of-function of Pi21. In this study, comparative transcriptome profiling of the Pi21-RNAi transgenic rice line and Nipponbare with M. oryzae infection at different time points (0, 12, 24, 48, and 72 hpi) were investigated using RNA sequencing. The results generated 43,222 unique genes mapped to the rice genome. In total, 1109 differentially expressed genes (DEGs) were identified between the Pi21-RNAi line and Nipponbare with M. oryzae infection, with 103, 281, 209, 69, and 678 DEGs at 0, 12, 24, 48, and 72 hpi, respectively. Functional analysis showed that most of the DEGs were involved in metabolism, transport, signaling, and defense. Among the genes assigned to plant—pathogen interaction, we identified 43 receptor kinase genes associated with pathogen-associated molecular pattern recognition and calcium ion influx. The expression levels of brassinolide-insensitive 1, flagellin sensitive 2, and elongation factor Tu receptor, ethylene (ET) biosynthesis and signaling genes, were higher in the Pi21-RNAi line than Nipponbare. This suggested that there was a more robust PTI response in Pi21-RNAi plants and that ET signaling was important to rice blast resistance. We also identified 53 transcription factor genes, including WRKY, NAC, DOF, and ERF families that show differential expression between the two genotypes. This study highlights possible candidate genes that may serve a function in the partial rice blast resistance mediated by the loss-of-function of Pi21 and increase our understanding of the molecular mechanisms involved in partial resistance against M. oryzae.
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Design, synthesis and fungicidal activity of novel 2-substituted aminocycloalkylsulfonamides

Design, synthesis and fungicidal activity of novel 2-substituted aminocycloalkylsulfonamides | Rice Blast | Scoop.it
A series of novel 2-substituted aminocycloalkylsulfonamides were designed and synthesized by highly selective N-alkylation reaction, whose structures were characterized by 1H NMR, 13C NMR and HRMS. Among them, the configuration of compounds III12 and III20 were confirmed by X-ray single crystal diffraction. Bioassays demonstrated that the title compounds had considerable effects on different strains of Botrytis cinerea and Pyricularia grisea. Comparing with positive control procymidone (EC50 = 10.31 mg/L), compounds III28, III29, III30 and III31 showed excellent fungicidal activity against a strain of B. cinerea (CY-09), with EC50 values of 3.17, 3.04, 2.54 and 1.99 mg/L respectively. Their in vivo fungicidal activities were also better than the positive controls cyprodinil, procymidone, boscalid and carbendazim in pot experiments. Moreover, the fungicidal activity of III28 (EC50 = 4.62 mg/L) against P. grisea was also better than that of the positive control isoprothiolane (EC50 = 6.11 mg/L). Compound III28 would be great promise as a hit compound for further study based on the structure-activity relationship.
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Overexpression of a Pathogenesis-Related Protein 10 Enhances Biotic and Abiotic Stress Tolerance in Rice

Overexpression of a Pathogenesis-Related Protein 10 Enhances Biotic and Abiotic Stress Tolerance in Rice | Rice Blast | Scoop.it
Pathogenesis-related proteins play multiple roles in plant development and biotic and abiotic stress tolerance. Here, we characterize a rice defense related gene named “jasmonic acid inducible pathogenesis-related class 10” (JIOsPR10) to gain an insight into its functional properties. Semi-quantitative RT-PCR analysis showed up-regulation of JIOsPR10 under salt and drought stress conditions. Constitutive over-expression JIOsPR10 in rice promoted shoot and root development in transgenic plants, however, their productivity was unaltered. Further experiments exhibited that the transgenic plants showed reduced susceptibility to rice blast fungus, and enhanced salt and drought stress tolerance as compared to the wild type. A comparative proteomic profiling of wild type and transgenic plants showed that overexpression of JIOsPR10 led to the differential modulation of several proteins mainly related with oxidative stresses, carbohydrate metabolism, and plant defense. Taken together, our findings suggest that JIOsPR10 plays important roles in biotic and abiotic stresses tolerance probably by activation of stress related proteins.
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WD40-repeat protein MoCreC is essential for carbon repression and is involved in conidiation, growth and pathogenicity of Magnaporthe oryzae

WD40-repeat protein MoCreC is essential for carbon repression and is involved in conidiation, growth and pathogenicity of Magnaporthe oryzae | Rice Blast | Scoop.it
Carbon catabolite repression (CCR) is a common regulatory mechanism used by microorganisms to prioritize use of a preferred carbon source (usually glucose). The CreC WD40-repeat protein is a major component of the CCR pathway in Aspergillus nidulans. To clarify the function of the CreC ortholog from Magnaporthe oryzae in regulating gene expression important for pathogenesis, MoCreC was identified and genetically characterized. The vegetative growth rate of the MoCreC deletion mutant on various carbon sources was reduced. The MoCreC mutant produced fewer conidia and with about 60% of conidia having septation defects. Appressorium formation was impaired in the MoCreC mutant. Although some appressoria of the mutant could penetrate the leaf surface successfully, the efficiency of penetration and invasive growth of infection hyphae was reduced, resulting in attenuated virulence toward host plants. The CCR was defective as the mutant was more sensitive to allyl alcohol in the presence of glucose, and 2-deoxyglucose was unable to fully repress utilization of secondary carbon sources. qRT-PCR results indicated that the genes encoding cell wall degradation enzymes, such as β-glucosidase, feruloyl esterase and exoglucanase, were upregulated in MoCreC mutant. Taken together, we conclude that MoCreC is a major regulator of CCR and plays significant roles in regulating growth, conidiation, and pathogenicity of M. oryzae.
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IR8: The miracle rice which saved millions of lives - BBC News

IR8: The miracle rice which saved millions of lives - BBC News | Rice Blast | Scoop.it
It is 50 years since a newly-developed strain revolutionised rice farming.

Via Mary Williams
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Intracellular innate immune surveillance devices in plants and animals

Intracellular innate immune surveillance devices in plants and animals | Rice Blast | Scoop.it
Multicellular eukaryotes coevolve with microbial pathogens, which exert strong selective pressure on the immune systems of their hosts. Plants and animals use intracellular proteins of the nucleotide-binding domain, leucine-rich repeat (NLR) superfamily to detect many types of microbial pathogens. The NLR domain architecture likely evolved independently and convergently in each kingdom, and the molecular mechanisms of pathogen detection by plant and animal NLRs have long been considered to be distinct. However, microbial recognition mechanisms overlap, and it is now possible to discern important key trans-kingdom principles of NLR-dependent immune function. Here, we attempt to articulate these principles. We propose that the NLR architecture has evolved for pathogen-sensing in diverse organisms because of its utility as a tightly folded “hair trigger” device into which a virtually limitless number of microbial detection platforms can be integrated. Recent findings suggest means to rationally design novel recognition capabilities to counter disease.

Via Ryohei Thomas Nakano, Philip Carella
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Magnaporthe oryzae perennial ryegrass pathotype causes leaf spots and blight on Japanese forest grass in Ohio | Plant Disease

Magnaporthe oryzae perennial ryegrass pathotype causes leaf spots and blight on Japanese forest grass in Ohio | Plant Disease | Rice Blast | Scoop.it
Japanese forest grass (Hakonechloa macra) is a slow growing deciduous perennial C3 plant popularly used as a groundcover in shady landscapes. In August 2015, H. macra 'All Gold' plants grown in a commercial nursery in Ohio exhibited dark-brown to black 1-3 mm diameter necrotic spots on leaves that were surrounded by a brown halo. Leaf tips were blighted and twisted. Incubation of symptomatic leaves in a moist chamber induced grayish-white fungal sporulation. Spores were suspended in sterile water and spread onto PDA plates. Representative colonies were transferred to oatmeal agar medium and incubated at 21°C under constant light for 7 days. Developing colonies were dark gray and reached in average 5.0 cm diameter (n=3). The fungus produced a dark gray mat of conidiophores with small amounts of white, filamentous mycelium on the edges. Conidia were 3-celled, papillate at the wider end, and narrowed to a tip at the opposite end. Conidia measured (1) 23.7 to 35.2 (1) x (1) 6.07 to 9.45 (1) µm (n=50). Based on morphological characteristics, the fungus was identified as Magnaporthe oryzae (Couch & Kohn 2002). Identification of one representative isolate was confirmed by sequence comparison of the internal transcribed spacer region (ITS1-5.8S-ITS2) with sequences available in GenBank, resulting in 99% homology to M. oryzae (JQ747492.1) with 100% coverage (deposited in GenBank under accession no. KY070277). Since different host-specialized forms of M. oryzae can occur on gramineous crops, we aimed to further identify the isolate’s pathotype by means of pathogenicity testing and genetic characterization. Pathogenicity tests were conducted on 3 inoculated and 3 non-inoculated plants of each of the following species: 2-week old H. macra 'Aureola' and 'All Gold'; 2-week old perennial ryegrass; 7-week old wheat ‘Bravo’; 3-week old rice ‘Nipponbare’. All plants were inoculated by spraying the aboveground plant tissues with a suspension of 3x105 spores ml-1 in 0.05% v/v Tween 20 solution. Control plants received sterile aqueous 0.05% v/v Tween 20 solution. After inoculation, plants were maintained in a greenhouse at 28°C and 98% relative humidity. Straw-colored lesions surrounded by a dark necrotic border were observed on the inoculated H. macra blades four days post-inoculation followed by leaf tip blight one week post-inoculation. On perennial ryegrass, typical gray leaf spot symptoms were visible four days post-inoculation. On rice, no symptoms were observed. On wheat, bleaching of the spikes was observed one week post-inoculation. In all cases where symptomatic lesions were observed, incubation for 24 hours in a moist chamber induced abundant spore production. The pathogen was re-isolated from the symptomatic tissues and its identity confirmed by morphological observation, which in the case of H. macra fulfilled Koch's postulates. In all cases, control plants remained asymptomatic. The isolate was further tested with a LAMP PCR primer set specific to the M. oryzae perennial ryegrass pathotype (Villari et al. 2016), which resulted in positive amplification. M. oryzae perennial ryegrass pathotype is widely distributed on grasses in several regions of the U.S. (Uddin et al. 2003; Viji et al. 2001), however, to the best of our knowledge, this is the first published report of its occurrence on H. macra in Ohio. The ability of grass isolates to cross-infect important food crops under laboratory conditions highlights the need for epidemiological studies in field settings.
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Characterization of molecular identity and pathogenicity of rice blast fungus in Hunan province of China

Characterization of molecular identity and pathogenicity of rice blast fungus in Hunan province of China | Rice Blast | Scoop.it
The blast (Magnaporthe oryzae) resistance (R) gene is the most economical and environmental method to control rice blast disease. Characterization of molecular identity and pathogenicity of M. oryzae benefits the deployment of effective blast R genes. In order to identify blast R genes that would be effective in Hunan province,182 M. oryzae strains were analyzed with a Chinese differential system (CDS), repetitive element-based polymerase chain reaction (Rep-PCR), the presence and absence of avirulence (AVR) genes by PCR amplification with gene specific primers. Identified blast R genes were validated with 24 monogenic lines (MLs) carrying 24 major R genes.A total of 28 races (isolates) of M. oryzae was identified with CDS, and classified into 20 distinct groups with Rep-PCR. Interestingly, AVR-Pia, AVR-Pik, AVR-Pizt, AVR-Pib, and AVR-Pi9 were detected in more than 86.8% of the isolates; AVR-Pita1 was in 51.3% and AVR-Pii was in only 2.5%. In contrast, pathogenicity assays on 24 MLs demonstrated thatPi9, Piz5, Pikh, and Pikm were more effective with resistant frequencies of 91.6, 91, 87.9, and 87.3%, respectively; Pia, Piks, Pit, Pi12, Pib were less than 15%. These findings revealed the complexity of genetic basis of rice blast resistance, and shed light on useful blast R genes in Hunan province.
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Identification of blast resistance genes in 358 rice germplasms (Oryza sativa L.) using functional molecular markers

Rice blast, caused by the fungus Magnaporthe oryzae, is one of the most devastating diseases of rice (Oryza sativa L.), and neck blast is the most destructive phase of this disease. Although neck blast causes tremendous yield loss, little is known about the molecular mechanisms underlying the neck blast resistance. To address this issue, we collected 358 rice varieties from different ecotypes in China and assessed them for the neck blast resistance under natural conditions favoring disease development in Jining, Shandong Province. Our results showed that 124 (34.6%) and 234 (65.4%) varieties were resistant and susceptible to M. oryzae under natural field conditions, respectively. Among the 358 rice varieties that were screened for the presence of 13 major blast resistance (R) genes against M. oryzae by using functional markers, 259 varieties contained one to seven R genes. In addition, the relationship between the presence of R genes and the disease reactions was also investigated by integrative analysis of phenotyping and genotyping based on functional markers. Our results showed that the rice blast resistance gene Pi2 was significantly correlated with neck blast resistance. Furthermore, any of the 13 major blast R genes was absent from 32 rice varieties exhibited obvious neck blast resistance, which would be the potential materials for identifying novel neck blast R genes. Taken together, our findings provide insight into the distribution of the 13 major blast R genes in the tested Chinese rice germplasm resources, which will serve as a basis for developing rice blast resistant. Furthermore, 32 rice varieties exhibited neck blast resistance, but they did not harbor any of the 13 major blast R genes. In the future, these varieties may be used to identify novel neck blast R genes.
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Characterization and Fine Mapping of a Blast Resistant Gene Pi-jnw1 from the japonica Rice Landrace Jiangnanwan

Characterization and Fine Mapping of a Blast Resistant Gene Pi-jnw1 from the japonica Rice Landrace Jiangnanwan | Rice Blast | Scoop.it
Rice blast is a destructive disease caused by Magnaporthe oryzae, and it has a large impact on rice production worldwide. Compared with leaf blast resistance, our understanding of panicle blast resistance is limited. The japonica landrace Jiangnanwan from Taihu Lake region in China shows highly resistance to panicle and leaf blast. In this study, three generations (F2:5, F2:6, F2:7) consisting of 221 RILs (recombination inbreeding lines), developed from the cross of Jiangnanwan and Suyunuo, a susceptible-blast japonica variety, were evaluated for panicle blast resistance in the fields and leaf blast resistance in greenhouse in Nanjing in 2013, 2014 and 2015. A blast resistance gene Pi-jnw1 referring to panicle blast resistance and leaf blast resistance was identified in the three generations and located in the region of RM27273 and RM27381 in chromosome 11. The RIL18 line harboring Pi-jnw1 was selected to be backcrossed with Suyunuo to develop BC2F2 populations. According to the genotyping of 1,150 BC2F2 individuals and panicle blast and leaf blast resistance evaluation of 47 recombinants between RM27150 and RM27381, Pi-jnw1 was finally mapped to the 282 kb region between markers W28 and BS39. This study revealed that Jiangnanwan harboring a panicle blast and leaf blast resistance gene Pi-jnw1 could be a genetic source for breeding new rice cultivars with panicle blast resistance.
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Pathogenicity of isolates of Magnaporthe sp from wheat and grasses infecting seedlings and mature wheat plants in Argentina

Wheat Blast of wheat (Triticum aestivum), caused by Magnaporthe oryzae Triticum pathotype (MoT) (anamorph Pyricularia oryzae) is a destructive disease in the South American countries of Brazil, Paraguay and Bolivia. In Argentina, the fungus was recently mentioned on wheat and barley plants in the northeast part of the country, Buenos Aires and Corrientes Provinces, with a potential for spreading. This work aimed to study for the first time, the morphocultural and pathogenic characteristics of Magnaporthe sp. isolates collected from wheat and other herbaceous species in Argentina and three neighbouring countries (Paraguay, Brazil and Bolivia) and determine their aggressivity on wheat varieties. Statistical differences among isolates, culture media, and development conditions were found for conidia color, growth rate, size and sporulation rate. Pathogenicity tests performed on seedling plants with nineteen isolates of Magnaporthe sp. under greenhouse conditions showed a maximum disease severity of 55.30% and 66.67% for the two varieties tested, BIOINTA 3004 and Baguette 18. Weed and grass isolates were infectious on wheat, demonstrating their potential epidemiological role on the disease. Spike, disease severity was 34.55% for the host/pathogen interaction of BIOINTA 3004/PY22. Observed symptoms included partial or total spike bleaching, and glume and rachis discoloration. The 1000 grain weight was significantly reduced (38.46 and 63.09%) for both cultivars, respectively. The disease affected grain germination, which fell to 65.87% for seeds infected with the PYAR22 isolate. Symptoms observed in infected grains were partial spotting, grain softening, and rot symptoms with the presence of a greyish mold
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Impact of fungicide and insecticide use on non-target aquatic organisms in rice paddy fields

The intensive use of plant protection products in rice paddy fields ( Oryza sativa L.) has caused concern about the environmental impact on communities of non-target organisms that are natural inhabitants in these agroecosystems. The purpose of this review is to analyze the data currently available in the literature about some important fungicides and insecticides (such as trifloxystrobin, tebuconazole, tricyclazole, lambda-cyhalothrin, and thiamethoxam), which are currently used to control pests and diseases in rice paddy fields, as well as their effects on the community of non-target aquatic organisms.
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MoCDC14 is important for septation during conidiation and appressorium formation in Magnaporthe oryzae

MoCDC14 is important for septation during conidiation and appressorium formation in Magnaporthe oryzae | Rice Blast | Scoop.it
As a typical foliar pathogen, appressorium formation and penetration are critical steps in the infection cycle of Magnaporthe oryzae. Because appressorium formation and penetration are closely co-regulated with cell cycle and Cdc14 phosphatases have antagonistic relationship with CDKs on proteins related to mitotic exits and cytokinesis, in this study we functionally characterized the MoCDC14 gene in M. oryzae. The Mocdc14 deletion mutant was significantly reduced in growth rate and conidiation. It also was defective in septum formation and nuclear distribution. Septation was irregular in Mocdc14 hyphae and hyphal compartments became multi-nucleate. Mutant conidia often had incomplete septa or lacked any septum. During appressorium formation, the septum delimiting appressoria from the rest of germ tubes was often formed far away from the neck of appressoria or not formed at all. Unlike the wild type, some mutant appressoria had more than one nuclei at 24 h. Besides appressoria, melanization occurred to parts of germ tubes and conidia, depending on the irregular position of the appressorium-delimiting septum. The Mocdc14 mutant also was defective in glycogen degradation during appressorium formation and appressorial penetration of intact plant cells. Similar defects in septum formation, melanization, and penetration were observed with appressorium-like structures formed at hyphal tips in the Mocdc14 mutant. Often a long fragment of mutant hyphae was melanized together with the apical appressorium-like structures. These results indicate that MoCDC14 plays a critical role in septation, nuclear distribution, and pathogenesis in M. oryzae, and proper septum formation during conidiogenesis and appressorium formation requires the MoCdc14 phosphatase. This article is protected by copyright. All rights reserved

Via Philip Carella
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Frontiers | Characterization and Genetic Analysis of Rice Mutant crr1 Exhibiting Compromised Non-host Resistance to Puccinia striiformis f. sp. tritici (Pst) | Plant Biotic Interactions

Frontiers | Characterization and Genetic Analysis of Rice Mutant crr1 Exhibiting Compromised Non-host Resistance to Puccinia striiformis f. sp. tritici (Pst) | Plant Biotic Interactions | Rice Blast | Scoop.it
Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of wheat in China. Rapid change to virulence following release of resistant cultivars necessitates ongoing discovery and exploitation of new resistance resources. Considerable effort has been directed at non-host resistance (NHR) which is believed to be durable. In the present study we identified rice mutant crr1 (compromised resistance to rust 1) that exhibited compromised NHR to Pst. Compared with wild type rice variety Nipponbare, crr1 mutant displayed a threefold increase in penetration rate by Pst, and enhanced hyphal growth. The pathogen also developed haustoria in crr1 mesophyll cells, but failed to sporulate. The response to the adapted rice pathogen Magnaporthe oryzae was unchanged in crr1 relative to the wild type. Several defense-related genes involved in the SA- and JA-mediated defense pathways response and in phytoalexin synthesis (such as OsPR1a, OsLOX1, and OsCPS4) were more rapidly and strongly induced in infected crr1 leaves than in the wild type, suggesting that other layers of defense are still in effect. Genetic analysis and mapping located the mutant loci at a region between markers ID14 and RM25792, which cover about 290 kb genome sequence on chromosome 10. Further fine mapping and cloning of the locus should provide further insights into NHR to rust fungi in rice, and may reveal new strategies for improving rust resistance in wheat.

Via Philip Carella
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Marker-assisted breeding of the rice restorer line Wanhui 6725 for disease resistance, submergence tolerance and aromatic fragrance

Marker-assisted breeding of the rice restorer line Wanhui 6725 for disease resistance, submergence tolerance and aromatic fragrance | Rice Blast | Scoop.it
Here we report the introduction and pyramiding of disease resistance genes Xa27 and Pi9, submergence tolerance gene Sub1A and aromatic fragrance gene badh2.1 in WH421 through backcrossing and marker-assisted selection. The newly developed introgression rice line was designated as Wanhui 6725 (WH6725), which theoretically possesses 95.0% genetic background of MH725. WH6725 and its hybrid rice conferred disease resistance to both blast and bacterial blight diseases and showed tolerance to submergence for over 14 days without significant loss of viability. Compared with non-aromatic rice MH725, WH6725 has strong aromatic fragrance. The major important agronomic traits and grain quality of WH6725 and its hybrid rice obtained in field trials were similar to those of MH725 and the control hybrid rice, indicating that WH6725 is as good as MH725 when it is used as a restorer line for three-line hybrid rice production.
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Economic and Environmental Impact of Rice Blast Pathogen (Magnaporthe oryzae) Alleviation in the United States

Economic and Environmental Impact of Rice Blast Pathogen (Magnaporthe oryzae) Alleviation in the United States | Rice Blast | Scoop.it
Rice blast (Magnaporthe oryzae) is a key concern in combating global food insecurity given the disease is responsible for approximately 30% of rice production losses globally—the equivalent of feeding 60 million people. These losses increase the global rice price and reduce consumer welfare and food security. Rice is the staple crop for more than half the world’s population so any reduction in rice blast would have substantial beneficial effects on consumer livelihoods. In 2012, researchers in the US began analyzing the feasibility of creating blast-resistant rice through cisgenic breeding. Correspondingly, our study evaluates the changes in producer, consumer, and environmental welfare, if all the rice produced in the Mid-South of the US were blast resistant through a process like cisgenics, using both international trade and environmental assessment modeling. Our results show that US rice producers would gain 69.34 million dollars annually and increase the rice supply to feed an additional one million consumers globally by eliminating blast from production in the Mid-South. These results suggest that blast alleviation could be even more significant in increasing global food security given that the US is a small rice producer by global standards and likely experiences lower losses from blast than other rice-producing countries because of its ongoing investment in production technology and management. Furthermore, results from our detailed life cycle assessment (LCA) show that producing blast-resistant rice has lower environmental (fossil fuel depletion, ecotoxicity, carcinogenics, eutrophication, acidification, global warming potential, and ozone depletion) impacts per unit of rice than non-blast resistant rice production. Our findings suggest that any reduction in blast via breeding will have significantly positive impacts on reducing global food insecurity through increased supply, as well as decreased price and environmental impacts in production.
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Clarification of the Antagonistic Effect of the Lipopeptides Produced by Bacillus amyloliquefaciens BPD1 against Pyricularia oryzae via In Situ MALDI-TOF IMS Analysis

Clarification of the Antagonistic Effect of the Lipopeptides Produced by Bacillus amyloliquefaciens BPD1 against Pyricularia oryzae via In Situ MALDI-TOF IMS Analysis | Rice Blast | Scoop.it
This study tried to clarify the antagonistic effect of the lipopeptides secreted by Bacillus amyloliquefaciens strain BPD1 (Ba-BPD1) against Pyricularia oryzae Cavara (PO). To determine the major antifungal lipopeptides effective against PO, single and dual cultures were carried out in solid-state media. The matrix-assisted laser desorption/ionization–time of flight imaging mass spectrometry (MALDI-TOF IMS) was used to identify the most effective lipopeptide in situ. Meanwhile, the morphology of pathogen fungi treated with lipopeptides was observed via the SEM. Of the three lipopeptide families, surfactin, iturin, and fengycin, the last was identified as the most effective for inhibiting mycelium growth and conidial germination of PO. The conidia and hyphae of fengycin-treated PO were shown to become deformed and tumorous under exposure. This study provides insights into the antagonistic effect of Ba-BPD1 against fungal phytopathogens. Such insights are helpful in the development of reagents for biological control applications
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Transcriptional Profiling of Rice Treated with MoHrip1 Reveal the Function of Protein Elicitor in Enhancement of Disease Resistance and Plant Growth

Transcriptional Profiling of Rice Treated with MoHrip1 Reveal the Function of Protein Elicitor in Enhancement of Disease Resistance and Plant Growth | Rice Blast | Scoop.it
MoHrip1 is a protein elicitor isolated from Magnaporthe oryzae and was found to induce blast-resistance in rice. To investigate the comprehensive functions of MoHrip1, next-generation sequencing (NGS)-based digital gene expression (DGE) profiling was performed to collect the transcriptional data of differentially expressed genes (DEGs) induced by MoHrip1. A total of 308 genes were identified with differential expression, and 80 genes were predicted to be induced specifically by MoHrip1. Among these 308 genes, a series of genes associated with the salicylic acid (SA) pathway, phytoalexin, transcription factors, and pathogen-related proteins were identified. Both the SA signaling pathway and the gibberellin (GA) pathway were activated, while the jasmonic acid (JA) signaling pathway was repressed. The contents of endogenous SA and GA and the morphological characteristics of the rice after treatment were measured to provide evidence supporting the predictions made based on the DGE data. The 80 genes mentioned above might be candidate genes for studying interactions with MoHrip1. The transcriptional data provided global effect information in rice induced by MoHrip1, and all the results demonstrated that MoHrip1 could induce pathogen resistance and promote plant growth by regulating the contents of SA and GA directly or indirectly.

Via Philip Carella
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How can rice genetics benefit from rice-domestication study?

How can rice genetics benefit from rice-domestication study? | Rice Blast | Scoop.it
Uncovering the puzzle of the origin and domestication process of cultivated rice has greatly impacted rice genetics, but comprehensively exploiting elite alleles from both wild species and domesticated varieties for modern rice breeding is still a long-term ongoing study.
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Unravelling the biosynthesis of pyriculol in the rice blast fungus Magnaporthe oryzae

Unravelling the biosynthesis of pyriculol in the rice blast fungus Magnaporthe oryzae | Rice Blast | Scoop.it
Pyriculol was isolated from the rice blast fungus Magnaporthe oryzae and found to induce lesion formation on rice leaves. These findings suggest that it could be involved in virulence. The gene MoPKS19 was identified to encode a polyketide synthase essential for the production of the polyketide pyriculol in the rice blast fungus Magnaporthe oryzae. The transcript abundance of MoPKS19 correlates with the biosynthesis rate of pyriculol in a time-dependent manner. Furthermore, gene inactivation of MoPKS19 resulted in a mutant unable to produce pyriculol, pyriculariol and their dihydro derivatives. Inactivation of a putative oxidase-encoding gene MoC19OXR1, which was found to be located in the genome close to MoPKS19, resulted in a mutant exclusively producing dihydro pyriculol and Dihydro pyriculariol. By contrast, overexpression of MoC19OXR1 resulted in a mutant strain only producing pyriculol. The MoPKS19 cluster, furthermore, comprises two transcription factors MoC19TRF1 and MoC19TRF2, which were both found individually to act as negative regulators repressing gene expression of MoPKS19. Additionally, extracts of ΔMopks19 and ΔMoC19OXR1 made from axenic cultures failed to induce lesions on rice leaves compared to extracts of the wild type strain. Consequently, pyriculol and its isomer pyriculariol appear to be the only lesion inducing secondary metabolites produced by MoWT under these culture conditions. Interestingly, the mutants unable to produce pyriculol and pyriculariol were as pathogenic as MoWT, demonstrating that pyriculol is not required for infection.
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Identification of blast resistant rice (oryza sativa l.) genotypes in indigenous and exotic germplasm and validation of pi gene linked molecular markers

Rice Blast, a most devastating disease of Rice caused by Magnaporthe grisea can be effectively managed by use of resistant rice genotypes. Availability of resistant donors and validated molecular markers are essential to develop resistant cultivars against different races and to pyramid the resistant genes, In the present investigation, 312 indigenous and 65 exotic germplasm lines were evaluated against blast resistance at RARS, Jagtial. More percentage (83%) of exotic germplasm showed resistance to rice blast disease compared to indigenous germplasm (46%). Three genotypes (JGL23710, JGL23713 and JGL23714) in indigenous germplasm and two genotypes (IR09N500 and IR12M101) in exotic germplasm were immune to rice blast disease. "These can be used as donor genetic stock for development of highly resistant rice cultivars with high yields". Among five linked markers studied for Pi-1 gene, one marker RM6094 was able to identify resistant genotypes at allelic level and for Pi-2 gene, RM527 was validated in four genotypes out of six genotypes used. This information will help rice breeders to improve the resistance to rice blast by marker assisted selection.
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