Monitoring of Brazilian wheat blast field populations reveals resistance to QoI, DMI, and SDHI fungicides

ABSTRACTThe blast fungus Magnaporthe oryzae is comprised of lineages that exhibit varying degrees of specificity on about 50 grass hosts, including rice, wheat and barley. Reliable diagnostic tools are essential given that the pathogen has a propensity to jump to new hosts and spread to new geographic regions. Of particular concern is wheat blast, which has suddenly appeared in Bangladesh in 2016 before spreading to neighboring India. In these Asian countries, wheat blast strains are now co-occurring with the destructive rice blast pathogen raising the possibility of genetic exchange between these destructive pathogens. We assessed the recently described MoT3 diagnostic assay and found that it did not distinguish between wheat and rice blast isolates from Bangladesh. The assay is based on primers matching the WB12 sequence corresponding to a fragment of the M. oryzae MGG_02337 gene annotated as a short chain dehydrogenase. These primers could not reliably distinguish between wheat and rice blast isolates from Bangladesh based on DNA amplification experiments performed in separate laboratories in Bangladesh and in the UK. In addition, comparative genomics of the WB12 sequence revealed a complex underlying genetic structure with related sequences across M. oryzae strains and in both rice and wheat blast isolates. We, therefore, caution against the indiscriminate use of this assay to identify wheat blast.

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Conidia sporulation of Pyricularia oryzae in segments of wheat plants under six different temperatures

Ciência Rural ◽

10.1590/0103-8478cr20190573 ◽

2020 ◽

Vol 50 (4) ◽

Author(s):

Marcos Kovaleski ◽

João Leodato Nunes Maciel ◽

Gustavo Bilibio dos Santos ◽

Alieze Nascimento da Silva ◽

Carolina Cardoso Deuner

Keyword(s):

High Temperature ◽

Petri Dish ◽

Pyricularia Oryzae ◽

Causal Agent ◽

Temperature Conditions ◽

Wheat Blast ◽

Conidia Production ◽

Different Temperatures

ABSTRACT: Wheat blast is known for developing itself more intensely under relatively high temperature conditions but many aspects related to its epidemiology remain unknown. The objective of this research was to evaluate the sporulative capacity of Pyricularia oryzae Triticum (Pot), the causal agent of wheat blast, in tissues of wheat plants under different temperatures degrees. Wheat plants of the cultivar Anahuac 75, susceptible to blast, were inoculated in the stage of flowering with conidial suspensions (105 conidia/mL) of the Pot isolates Py 12.1.209 and Py 12.1.132. Seven days after the inoculation, plants were cut in the following segments: leaves, stems and rachis (with blast severity ranging from 40 to 60%). Groups of each one of the three plant segments with the lesions were disposed in Petri-dish moist chambers, that were submitted to six different temperature treatments (18, 21, 24, 27, 30 and 33 °C). The most appropriate model that related the conidia production with temperature was identified in the evaluations conducted with stems. The established equations allowed identifying that the highest production of conidia of Pot occurs between 24 and 27 °C.

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Cautionary Notes on Use of the MoT3 Diagnostic Assay for Magnaporthe oryzae Wheat and Rice Blast Isolates

Phytopathology ◽

10.1094/phyto-06-18-0199-le ◽

2019 ◽

Vol 109 (4) ◽

pp. 504-508 ◽

Cited By ~ 8

Author(s):

Dipali Rani Gupta ◽

Claudia Sarai Reyes Avila ◽

Joe Win ◽

Darren M. Soanes ◽

Lauren S. Ryder ◽

...

Keyword(s):

Magnaporthe Oryzae ◽

Rice Blast ◽

Dna Amplification ◽

Diagnostic Tools ◽

Diagnostic Assay ◽

Wheat Blast ◽

The United Kingdom ◽

New Hosts ◽

Grass Hosts ◽

Further Development

The blast fungus Magnaporthe oryzae is comprised of lineages that exhibit varying degrees of specificity on about 50 grass hosts, including rice, wheat, and barley. Reliable diagnostic tools are essential given that the pathogen has a propensity to jump to new hosts and spread to new geographic regions. Of particular concern is wheat blast, which has suddenly appeared in Bangladesh in 2016 before spreading to neighboring India. In these Asian countries, wheat blast strains are now co-occurring with the destructive rice blast pathogen raising the possibility of genetic exchange between these destructive pathogens. We assessed the recently described MoT3 diagnostic assay and found that it did not distinguish between wheat and rice blast isolates from Bangladesh. The assay is based on primers matching the WB12 sequence corresponding to a fragment of the M. oryzae MGG_02337 gene annotated as a short chain dehydrogenase. These primers could not reliably distinguish between wheat and rice blast isolates from Bangladesh based on DNA amplification experiments performed in separate laboratories in Bangladesh and in the United Kingdom. Specifically, all eight rice blast isolates tested in this study produced the WB12 amplicon. In addition, comparative genomics of the WB12 nucleotide sequence revealed a complex underlying genetic structure with related sequences across M. oryzae strains and in both rice and wheat blast isolates. We, therefore, caution against the indiscriminate use of this assay to identify wheat blast and encourage further development of the assay to ensure its value in diagnosis.

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The risk of wheat blast in rice-wheat-co-planting regions in China: MoO strains of Pyricularia oryzae cause typical symptom and host reaction on both wheat leaves and spikes

Phytopathology ◽

10.1094/phyto-10-20-0470-r ◽

2021 ◽

Author(s):

Shizhen Wang ◽

Jiaoyu Wang ◽

Zhen Zhang ◽

Zhongna Hao ◽

Xueming Zhu ◽

...

Keyword(s):

Global Warming ◽

Pyricularia Oryzae ◽

Wheat Cultivars ◽

Host Reaction ◽

Typical Symptom ◽

Wheat Blast ◽

Resistant Genes ◽

Wheat Leaves ◽

Cultivar Specificity ◽

Heading Stage

Triticum pathotype (MoT) of Magnaporthe oryzae (syn. Pyricularia oryzae) causes wheat blast, which has recently spread to Asia. To assess the potential risk of wheat blast in rice-wheat growing regions, we investigated the pathogenicity of 14 isolates of P. oryzae on 32 wheat cultivars, among which MoO isolates were completely avirulent on the wheat cultivars at 22℃, but caused various infection degrees at 25℃. These reactions at 25℃ were isolate- and cultivar- dependent like race-cultivar specificity which was also recognized at the heading stage and caused typical blast symptoms on spikes. Microscopic analyses indicated that a compatible MoO isolates produced appressoria and infection hyphae on wheat as on rice. By comparing transcriptomes in wheat-MoO interactions, a bulk of pathogen-related genes was up-/down- regulated in compatible and incompatible patterns, but that changes of gene transcription were more significant in compatible pattern. These results indicate that the temperature could influence the infection ratio of wheat with MoO, and some MoO strains could be potential pathogens that increase the risk for the outbreak of wheat blast in wheat-rice growing regions with global warming. In addition, certain wheat cultivars exhibited resistance and are assumed to carry promoting resistant genes to the MoO strains.

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