Evaluation of Rice Responses to the Blast Fungus Magnaporthe oryzae at Different Growth Stages

Rice blast, caused by the fungus Magnaporthe oryzae, is the most damaging disease for rice worldwide. However, the reactions of rice to M. oryzae at different growth stages are largely unknown. In the present study, two temperate japonica rice cultivars, M-202 and Nipponbare, were inoculated synchronously at different vegetative growth stages, V1 to V10. Plants of M-202 at each stage from V1 to reproductive stage R8 were inoculated with M. oryzae race (isolate) IB-49 (ZN61) under controlled conditions. Disease reactions were recorded 7 days postinoculation by measuring the percentage of diseased area of all leaves, excluding the youngest leaf. The results showed that the plants were significantly susceptible at the V1 to V4 stages with a disease severity of 26.7 to 46.8% and disease index of 18.62 to 37.76 for M-202. At the V1 to V2 stages, the plants were significantly susceptible with a disease a severity of 28.6 to 39.3% and disease index of 23.65 to 29.82 for Nipponbare. Similar results were observed when plants of M-202 were inoculated at each growth stage with a disease severity of 29.7 to 60.6% and disease index of 21.93 to 59.25 from V1 to V4. Susceptibility decreased after the V5 stage (severity 4.6% and index 2.17) and became completely resistant at the V9 to V10 stages and after the reproductive stages, suggesting that plants have enhanced disease resistance at later growth stages. These findings are useful for managing rice blast disease in commercial rice production worldwide.

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Management of Rice Blast (Magnaporthe Oryzae B. Couch) Using Bioagents and Fungicides Under Hill Rice Ecosystem of Uttarakhand State in India

Bangladesh Journal of Botany ◽

10.3329/bjb.v50i3.55853 ◽

2021 ◽

Vol 50 (3) ◽

pp. 713-716

Author(s):

H Rajashekara ◽

KK Mishra ◽

PK Mishra

Keyword(s):

Magnaporthe Oryzae ◽

Rice Blast ◽

Blast Disease ◽

Growth Stages ◽

Biological Control Agents ◽

Trichoderma Sp ◽

Rice Ecosystem ◽

Disease Pressure ◽

Different Growth Stages ◽

Chemical Fungicides

A field study was conducted during Kharif-2015 and 2016 on management of leaf and neck blast disease of rice caused by Magnaporthe oryzae under hill rice ecosystem. Different treatments including biological control agents like Trichoderma sp. and Pseudomonas sp. and chemical fungicides like tricyclozole, azoxystrobin and carbendazim were used at different growth stages of rice. Among the treatments, tricyclozole @ 0.06% was highly effective followed by azoxystrobin @ 0.1% with application immediately after appearance of disease. Trichoderma and Pseudomonas were not effective in reducing the disease pressure. Bangladesh J. Bot. 50(3): 713-716, 2021 (September)

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Carolina Foxtail (Alopecurus carolinianus): Susceptibility and Suitability as an Alternative Host to Rice Blast Disease (Magnaporthe oryzae [formerly M. grisea])

Plant Disease ◽

10.1094/pdis-92-4-0504 ◽

2008 ◽

Vol 92 (4) ◽

pp. 504-507 ◽

Cited By ~ 1

Author(s):

Y. Jia ◽

D. Gealy ◽

M. J. Lin ◽

L. Wu ◽

H. Black

Keyword(s):

Magnaporthe Oryzae ◽

Rice Blast ◽

Rice Blast Disease ◽

Blast Disease ◽

Artificial Inoculation ◽

Rice Cultivars ◽

Alternative Host ◽

Lesion Development ◽

Disease Symptoms ◽

Rice Leaves

Carolina foxtail (Alopecurus carolinianus) has not been reported to host Magnaporthe oryzae. A collection of Carolina foxtail obtained from several Arkansas locations over a 4-year period was inoculated with four races of the fungus under greenhouse conditions and, in all cases, inoculation resulted in the formation of irregular, yellow and brown lesions without obvious gray centers that are characteristic for blast on rice. Differences in these lesions were not observed among our collection. These lesions appeared to differ from typical blast lesions on inoculated rice leaves but were evident following artificial inoculation of Carolina foxtail in the greenhouse. M. oryzae races that differed in pathogenicity toward rice cultivars also displayed differences in lesion development on Carolina foxtail. The most virulent race on rice cultivars also produced lesions most rapidly on Carolina foxtail. These lesions developed more quickly on Carolina foxtail than on the most susceptible rice cultivars tested, including a susceptible California cultivar, M202. M. oryzae isolates cultured from these lesions in the infected Carolina foxtail caused typical disease symptoms of blast on inoculated rice cultivars. We suggest that Carolina foxtail is a new and previously unrecognized host for the blast pathogen.

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Development of blast resistant rice plants using CRISPR / Cas9 system for genome editing

10.34019/ufjf/te/2021/00037 ◽

2021 ◽

Author(s):

◽

Fabiano Touzdjian Pinheiro Kohlrausch Távora

Keyword(s):

Rice Blast ◽

Blast Resistance ◽

Rice Variety ◽

Susceptibility Genes ◽

Plant Diseases ◽

Blast Disease ◽

World Population ◽

Japonica Rice ◽

Rice Cultivars ◽

Short Period

Rice (Oryza sativa L.) is the main food crop for more than half of the world population but unfortunately, it is severely affected by blast, one of the most widespread and devastating plant diseases, caused by the fungus Magnaporthe oryzae. Hence, the development of rice cultivars with greater resistance to blast is one of the main focuses of breeding programs. However, due to the complex biology of the pathogen, rice cultivars genetically resistant to the fungus become susceptible in a short period of time. In this context, the knockout of rice susceptibility genes represents a flourishing approach to obtain rice cultivars with a broader and longer-lasting resistance to M. oryzae. The present study aimed to use the genomic editing technology - CRISPR/Cas9 system, for knocking-out genes engaged with rice susceptibility to fungal infection. From previous transcriptomics results of two semi-isogenic rice lines - NILs infected by M. oryzae, potential rice-blast susceptibility genes were selected. The prospection of candidate genes for gene editing was complemented by a comparative shotgun proteomic analysis of the protein profile of the interaction between IRBLi-F5 (susceptible) and IRBL5-M (resistant) NILs in early stages of M. oryzae infection, that revealed a specific set of proteins potentially associated with susceptibility. After the characterization and validation of gene expression by RT-qPCR of the most prominent candidates, the target genes OsDjA2, OsERF104 and OsPyl5 were selected and submitted to a functional validation via gene silencing in planta, using antisense oligonucleotides (ASO), in which a clear reduction of leaf symptoms was observed in the compatible identification. Subsequently, the model japonica rice variety Nipponbare was transformed with simplex CRISPR/Cas9 vectors aiming to the independent knockout of each target gene. The T1 progeny of rice-edited plants, homozygous for the null (loss of function)-mutation were tested for blast resistance. As expected, mutant plants showed a decrease of disease symptoms in comparison with control lines (transformant non-edited plants). The results obtained in this study can contribute for the development of rice cultivars resistant to blast disease, besides shedding light on new potential rice-blast susceptibility genes.

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Evaluation of different aqueous plant extracts against rice blast disease fungus (Magnaporthe oryzae)

Ife Journal of Science ◽

10.4314/ijs.v22i3.17 ◽

2021 ◽

Vol 22 (3) ◽

pp. 193-202

Author(s):

G.O. Agbowuro ◽

M. Aluko ◽

A.E. Salami ◽

S.O. Awoyemi

Keyword(s):

Disease Severity ◽

Plant Extracts ◽

Magnaporthe Oryzae ◽

Rice Blast ◽

Research Work ◽

Rice Blast Disease ◽

Blast Disease ◽

Calotropis Procera ◽

Datura Metel ◽

Angel’S Trumpet

The antifungal potentials of some medicinal plant leaf extracts have been established against fungal diseases. This research work was conducted to evaluate the effects of aqueous plant leaf extracts of five plants: Apple of Sodom (Calotropis procera), Neem tree (Azadirachta indica), Thorn Apple/Angel's trumpet (Datura metel), Aleo plant (Aleo vera) and Siam weed (Chromolaena odorata)) at different concentration (25, 50, and 100%) against rice blast disease (Magnaporthe oryzae) in-vitro and in-vivo. The research work was laid out in a split-split plot arrangement using a randomized complete block design with three replications. Data were collected for disease severity, disease incidence, number of tillers per plant, number of filled grains, the weight of 1000 grains, and panicle weight. The data collected were analyzed using IRRI STAR software (IRRI, 1979). Percentage inhibition was significantly higher at higher concentrations for all the aqueous plant extracts as compared to lower concentrations. The field trial result shows that there were significant differences among all the studied traits though at different levels for all the sources of variation. The leaf plant aqueous extracts at all the varied concentrations reduced the rate of disease severity and incidence while the number of tillers per plant, the number of filled grains, the weight of 1000 seeds, and panicle weight increased compared to control. The result revealed that Apple of Sodom (Calotropis procera) is the most efficient in combating rice blast disease followed by Neem tree (Azadirachta indica), Thorn Apple/Angel's trumpet (Datura metel), Aleo plant (Aleo vera), and Siam weed (Chromolaena odorata) in that other. These aqueous plant extracts can be used to manage rice blast disease at a low cost and it is ecofriendly compare to chemical fungicides. Keywords: Disease severity, Magnaporthe oryzae, Medicinal plants, Plant extracts, Rice

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Level of Endogenous Jasmonate is Critical for Durable Broad-Spectrum Disease Resistance Against Rice Blast in a Japonica Rice Variety, Ziyu44

10.21203/rs.3.rs-571828/v1 ◽

2021 ◽

Author(s):

Xingyu An ◽

Hui Zhang ◽

Jinlu Li ◽

Rui Yang ◽

Qianchun Zeng ◽

...

Keyword(s):

Disease Resistance ◽

Signaling Pathway ◽

Broad Spectrum ◽

Rice Blast ◽

Blast Resistance ◽

Rice Variety ◽

Blast Disease ◽

Japonica Rice ◽

Mycelium Growth ◽

Broad Spectrum Resistance

Abstract Background: The molecular mechanism of durable and broad-spectrum resistance to rice blast disease in japonica rice variety is still very little known. Ziyu44, a local japonica rice variety in Yunnan Province of China, has shown durable broad-spectrum blast resistance for more than 30 years, and provides an opportunity for us to explore the molecular basis of broad-spectrum resistance to rice blast in japonica rice variety.Methods and Results: We conducted a comparative study of mycelium growth, aposporium formation, the accumulation of salicylate(SA), jasmonate(JA) and H2O2, the expression of SA- and JA-associated genes between Ziyu44 and susceptible variety Jiangnanxiangnuo (JNXN) upon M. oryzae infection. We found that appressorium formation and invasive hyphae extention were greatly inhibited in Ziyu 44 leaves compared with that in JNXN leaves. Both Ziyu 44 and JNXN plants maintained high levels of baseline SA and did not show increased accumulation of SA after inoculation with M. oryzae, while the levels of baseline JA in Ziyu 44 and JNXN plants were relatively low, and the accumulation of JA exhibited markedly increased in Ziyu 44 plants upon M. oryzae infection. The expression levels of key genes involving JA and SA signaling pathway OsCOI1b, OsNPR1, OsMPK6 as well as pathogenesis-related (PR) genes OsPR1a, OsPR1b and OsPBZ1, were markedly up-regulated in Ziyu44. Conclusions: The level of endogenous JA is critical for synchronous activation of SA and JA signaling pathway, up-regulating PR gene expression and enhancing disease resistance against rice blast in Ziyu44.

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Osa-miR162a balances rice yield and resistance to Magnaporthe oryzae

10.21203/rs.2.22473/v1 ◽

2020 ◽

Author(s):

Xu-Pu Li ◽

Xiao-Chun Ma ◽

He Wang ◽

Yong Zhu ◽

Xin-Xian Liu ◽

...

Keyword(s):

Magnaporthe Oryzae ◽

Rice Blast ◽

Rice Yield ◽

Blast Resistance ◽

Blast Disease ◽

Mirna Biogenesis ◽

Trade Off ◽

Rice Blast Resistance ◽

Defense Related Gene ◽

Transgenic Lines

Abstract MicroRNAs (miRNAs) play essential roles in rice immunity against Magnaporthe oryzae, the causative agent of rice blast disease. Osa-miR162a targets Dicer-like 1 (DCL1) genes, which play vital roles in miRNA biogenesis and act as negative regulators in rice immunity. Here we demonstrate that Osa-miR162a improves rice immunity against M. oryzae and balances the trade-off between rice yield and resistance. Overexpression of Osa-miR162a compromises rice susceptibility to M. oryzae accompanying enhanced induction of defense-related genes and accumulation of hydrogen peroxide (H2O2). In contrast, blocking miR162 by overexpressing a target mimic of miR162 enhances susceptibility to blast fungus associating with compromised induction of defense-related gene expression and H2O2 accumulation. Moreover, the transgenic lines overexpressing Osa-miR162a display decreased seed setting rate resulting in reduced yield per plant, whereas blocking miR162 leads to an increased number of grains per panicle, resulting in increased yield per plant. Altered accumulation of miR162 had limited impact on the expression of OsDCL1. Together, our results indicate that Osa-miR162a improves rice blast resistance and plays a role in the balance of trade-off between resistance and yield.

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Role of two metacaspases in development and pathogenicity of the Rice Blast fungus, Magnaporthe oryzae

10.1101/2020.12.10.420794 ◽

2020 ◽

Author(s):

Jessie Fernandez ◽

Victor Lopez ◽

Lisa Kinch ◽

Mariel A. Pfeifer ◽

Hillery Gray ◽

...

Keyword(s):

Cell Death ◽

Food Security ◽

Life Cycle ◽

Magnaporthe Oryzae ◽

Rice Blast ◽

Rice Blast Disease ◽

Blast Disease ◽

Complex Life Cycle ◽

Insight Into

ABSTRACTRice blast disease caused by Magnaporthe oryzae is a devastating disease of cultivated rice worldwide. Infections by this fungus lead to a significant reduction in rice yields and threats to food security. To gain better insight into growth and cell death in M. oryzae during infection, we characterized two predicted M. oryzae metacaspase proteins, MoMca1 and MoMca2. These proteins appear to be functionally redundant and are able to complement the yeast Yca1 homologue. Biochemical analysis revealed that M. oryzae metacaspases exhibited Ca2+ dependent caspase activity in vitro. Deletion of both MoMca1 and MoMca2 in M. oryzae resulted in reduced sporulation, delay in conidial germination and attenuation of disease severity. In addition, the double ΔMomca1mca2 mutant strain showed increased radial growth in the presence of oxidative stress. Interestingly, the ΔMomca1mca2 strain showed an increase accumulation of insoluble aggregates compared to the wild-type strain during vegetative growth. Our findings suggest that MoMca1 and MoMca2 promote the clearance of insoluble aggregates in M. oryzae, demonstrating the important role these metacaspases have in fungal protein homeostasis. Furthermore, these metacaspase proteins may play additional roles, like in regulating stress responses, that would help maintain the fitness of fungal cells required for host infection.IMPORTANCEMagnaporthe oryzae causes rice blast disease that threatens global food security by resulting in the severe loss of rice production every year. A tightly regulated life cycle allows M. oryzae to disarm the host plant immune system during its biotrophic stage before triggering plant cell death in its necrotrophic stage. The ways M. oryzae navigates its complex life cycle remains unclear. This work characterizes two metacaspase proteins with peptidase activity in M. oryzae that are shown to be involved in the regulation of fungal growth and development prior to infection by potentially helping maintain fungal fitness. This study provides new insight into the role of metacaspase proteins in filamentous fungi by illustrating the delays in M. oryzae morphogenesis in the absence of these proteins. Understanding the mechanisms by which M. oryzae morphology and development promote its devastating pathogenicity may lead to the emergence of proper methods for disease control.

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Differential Tolerance of Clearfield Rice Cultivars to Imazamox

Weed Technology ◽

10.1614/wt-d-10-00129.1 ◽

2011 ◽

Vol 25 (2) ◽

pp. 192-197 ◽

Cited By ~ 17

Author(s):

Jason A. Bond ◽

Timothy W. Walker

Keyword(s):

Growth Stage ◽

Rice Yield ◽

Field Studies ◽

First Year ◽

Growth Stages ◽

Rice Cultivars ◽

Rough Rice ◽

Rice Yields ◽

Clearfield Rice ◽

Two Hybrid

Field studies were conducted to compare the response of one inbred (‘CL161’) and two hybrid (‘CLXL729’ and ‘CLXL745’) Clearfield (CL) rice cultivars to imazamox. Imazamox was applied at 44 and 88 g ai ha−1to rice in the panicle initiation (PI) and PI plus 14 d (PI + 14) growth stages and at 44 g ha−1to rice in the midboot growth stage. Maturity of hybrid CL cultivars was delayed following imazamox at 44 g ha−1applied at PI + 14 and midboot. Furthermore, imazamox at 44 g ha−1, applied at midboot, delayed maturity of CLXL745 more than CLXL729. Expressed as a percentage of the weed-free control plots, rough rice yields for CLXL729 were 91% following imazamox at 44 g ha−1applied at PI + 14, 78% following imazamox at 44 g ha−1applied at midboot, and 77% for imazamox at 88 g ha−1applied at PI + 14. Rough rice yield for CLXL745 was 77 to 92% of the control following all imazamox treatments. All imazamox treatments reduced CLXL745 rough rice yield compared with CL161. Rough rice yield, pooled across CL cultivar, varied with imazamox treatment between years, and these differences may have been a consequence of lower temperatures and solar radiation in the first year. Hybrid CL cultivars CLXL729 and CLXL745 were less tolerant than was CL161 when imazamox was applied at nonlabeled rates (88 g ha−1) and/or timings (PI + 14 or midboot). Because of variability in rice growth stages and irregularities in imazamox application in commercial fields, inbred CL cultivars should be planted where an imazamox application will likely be required.

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Polycomb repressive complex 2 coordinates with Sin3 histone deacetylase complex to epigenetically reprogram genome-wide expression of effectors and regulate pathogenicity in Magnaporthe oryzae

10.1101/2021.03.21.436344 ◽

2021 ◽

Author(s):

Zhongling Wu ◽

Jiehua Qiu ◽

Huanbin Shi ◽

Chuyu Lin ◽

Jiangnan Yue ◽

...

Keyword(s):

Histone Deacetylase ◽

Magnaporthe Oryzae ◽

Rice Blast ◽

Growth Stage ◽

Invasive Growth ◽

Polycomb Repressive Complex ◽

Host Environment ◽

Polycomb Repressive Complex 2 ◽

Genome Wide ◽

Genome Wide Expression

The strict suppression and reprogramming of gene expression are necessary at different development stages and/or in response to environment stimuli in eukaryotes. In Rice Magnaporthe oryzae pathosystem, effectors from pathogen are kept transcriptionally silenced in the vegetative growth stage and are highly expressed during invasive growth stage to adapt to the host environment. However, the mechanism of how such effectors are stably repressed in the vegetative stage and its roles during rice blast infection remain unclear so far. Here, we showed that all subunits of Polycomb Repressive Complex 2 are required for such repression by direct H3K27me3 occupancy and pathogenic process in M. oryzae. Suppression of polycomb-mediated H3K27me3 causes an improper induction of effectors during vegetative growth thus simulating a host environment. Notably, the addition subunit P55 not only acts as the bridge to connect with core subunits to form a complex in M. oryzae, but also recruits Sin3 histone deacetylase complex to prompt H3K27me3 occupancy for stable maintenance of transcriptional silencing of the target genes in the absence of PRC1. In contrast, during invasive growth stage, the repressed state of effectors chromatin can be partially erased during pathogenic development resulting in transcriptional activation of effectors therein. Overall, Polycomb repressive complex 2 coordinates with Sin3 histone deacetylase complex to epigenetically reprogram genome-wide expression of effectors, which act as molecular switch to memorize the host environment from vegetative to invasive growth, thus contributing to the infection of rice blast.

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