Isolation and Characterization of Avirulence Genes in Magnaporthe oryzae

Magnaporthe oryzae is a fungal pathogen contributing to rice blast diseases globally via their Avr (avirulence) gene. Although the occurrence of M. oryzae has been reported in Sarawak since several decades ago, however, none has focused specifically on Avr genes, which confer resistance against pathogen associated molecular pattern-triggered immunity (PTI) in host. The objective of this study is to isolate Avr genes from M. oryzae 7’ (a Sarawak isolate) that may contribute to susceptibility of rice towards diseases. In this study, AvrPiz-t, AVR-Pik, Avr-Pi54, and AVR-Pita1 genes were isolated via PCR and cloning approaches. The genes were then compared with set of similar genes from related isolates derived from NCBI. Results revealed that all eight Avr genes (including four other global isolates) shared similar N-myristoylation site and a novel motif. 3D modeling revealed similar β-sandwich structure in AvrPiz-t and AVR-Pik despite sequence dissimilarities. In conclusion, it is confirmed of the presence of these genes in the Sarawak (M. oryzae) isolate. This study implies that Sarawak isolate may confer similar avirulence properties as their counterparts worldwide. Further R/Avr gene-for-gene relationship studies may aid in strategic control of rice blast diseases in future.

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Geographic Distribution of Avirulence Genes of the Rice Blast Fungus Magnaporthe oryzae in the Philippines

Microorganisms ◽

10.3390/microorganisms7010023 ◽

2019 ◽

Vol 7 (1) ◽

pp. 23 ◽

Cited By ~ 1

Author(s):

Ana Lopez ◽

Tapani Yli-Matilla ◽

Christian Cumagun

Keyword(s):

Geographic Distribution ◽

Magnaporthe Oryzae ◽

Rice Blast ◽

Rice Blast Fungus ◽

The Philippines ◽

R Genes ◽

Avirulence Genes ◽

Geographic Locations ◽

Avr Genes ◽

Pcr Test

A total of 131 contemporary and 33 reference isolates representing a number of multi-locus genotypes of Magnaporthe oryzae were subjected to a PCR test to detect the presence/absence of avirulence (Avr) genes. Results revealed that the more frequently occurring genes were Avr-Pik (81.50%), Avr-Pita (64.16%) and Avr-Pii (47.98%), whereas the less frequently occurring genes were Avr-Pizt (19.08%) and Avr-Pia (5.20%). It was also laid out that the presence of Avr genes in M. oryzae is strongly associated with agroecosystems where the complementary resistant (R) genes exist. No significant association, however, was noted on the functional Avr genes and the major geographic locations. Furthermore, it was identified that the upland varieties locally known as “Milagrosa” and “Waray” contained all the R genes complementary to the Avr genes tested.

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Effector genes in Magnaporthe oryzae Triticum as Potential Targets for Incorporating Blast Resistance in Wheat

Plant Disease ◽

10.1094/pdis-10-21-2209-re ◽

2021 ◽

Author(s):

Monica Navia-Urrutia ◽

Gloria Mosquera ◽

Rebekah Ellsworth ◽

Mark Farman ◽

Harold N. Trick ◽

...

Keyword(s):

Resistance Genes ◽

Magnaporthe Oryzae ◽

Rice Blast ◽

Blast Resistance ◽

Genetic Resistance ◽

Avirulence Gene ◽

Avirulence Genes ◽

Rice Blast Resistance ◽

Effector Genes ◽

Transgenic Lines

Wheat blast (WB), caused by Magnaporthe oryzae Triticum pathotype, recently emerged as a destructive disease that threatens global wheat production. Since few sources of genetic resistance have been identified in wheat, genetic transformation of wheat with rice blast resistance genes could expand resistance to WB. We evaluated the presence/absence of homologs of rice blast effector genes in Triticum isolates with the aim of identifying avirulence genes in field populations whose cognate rice resistance genes could potentially confer resistance to WB. We also assessed presence of the wheat pathogen AVR-Rmg8 gene, and identified new alleles. A total of 102 isolates collected in Brazil, Bolivia and Paraguay from 1986 to 2018 were evaluated by PCR using 21 pairs of gene-specific primers. Effector gene composition was highly variable, with homologs to AvrPiz-t, AVR-Pi9, AVR-Pi54 and ACE1 showing the highest amplification frequencies (>94%). We identified Triticum isolates with a functional AvrPiz-t homolog that triggers Piz-t-mediated resistance in the rice pathosystem, and produced transgenic wheat plants expressing the rice Piz-t gene. Seedlings and heads of the transgenic lines were challenged with isolate T25 carrying functional AvrPiz-t. Although slight decreases in the percentage of diseased spikelets and leaf area infected were observed in two transgenic lines, our results indicated that Piz-t did not confer useful WB resistance. Monitoring of avirulence genes in populations is fundamental to identifying effective resistance genes for incorporation into wheat by conventional breeding or transgenesis. Based on avirulence gene distributions, rice resistance genes Pi9 and Pi54 might be candidates for future studies.

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Association Genetics Reveals Three Novel Avirulence Genes from the Rice Blast Fungal Pathogen Magnaporthe oryzae

The Plant Cell ◽

10.1105/tpc.109.066324 ◽

2009 ◽

Vol 21 (5) ◽

pp. 1573-1591 ◽

Cited By ~ 242

Author(s):

Kentaro Yoshida ◽

Hiromasa Saitoh ◽

Shizuko Fujisawa ◽

Hiroyuki Kanzaki ◽

Hideo Matsumura ◽

...

Keyword(s):

Magnaporthe Oryzae ◽

Fungal Pathogen ◽

Rice Blast ◽

Association Genetics ◽

Avirulence Genes

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Identification of Magnaporthe oryzae Avirulence Genes to Three Rice Blast Resistance Genes

Plant Disease ◽

10.1094/pdis.2004.88.3.265 ◽

2004 ◽

Vol 88 (3) ◽

pp. 265-270 ◽

Cited By ~ 13

Author(s):

C. X. Luo ◽

Y. Fujita ◽

N. Yasuda ◽

K. Hirayae ◽

T. Nakajima ◽

...

Keyword(s):

Magnaporthe Oryzae ◽

Goodness Of Fit ◽

Blast Resistance ◽

Random Amplified Polymorphic Dna ◽

Rice Cultivars ◽

Avirulence Genes ◽

Rice Blast Resistance ◽

Parental Isolate ◽

Avr Gene ◽

Avr Genes

The segregation of avirulence/virulence was studied in 115 F1 progeny isolates of Magnaporthe oryzae from a cross of two field isolates on three Japanese race-differential rice cultivars Kanto 51, Fukunishiki, and Toride 1. The χ2 tests of goodness-of-fit for a 1:1 ratio indicated that avirulence on cvs. Kanto 51, Fukunishiki, and Toride 1 was under monogenic control. The relationship between the avirulence (Avr) gene in the parental isolate and the Avr gene in the standard isolate was investigated by using 100 lines each of three F3 families from the crosses of the rice cultivars Norin 3/Kanto 51, AK61/Fukunishiki, and Norin 3/Toride 1, respectively. Based on the resistant reactions of the F3 rice lines to the parental isolates and the standard isolates harboring three known Avr genes, three genetically independent Avr genes, AvrPik, AvrPiz, and AvrPiz-t, were identified. The three identified Avr genes were mapped using random amplified polymorphic DNA (RAPD) analysis, and a partial linkage map was constructed with 17 RAPD markers closely linked to the Avr genes. Twelve markers and AvrPik, three markers and AvrPiz, and two markers and AvrPiz-t, as well as mating locus MAT1, constructed linkage groups A, B, and C, respectively.

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Identification of a Novel Locus Rmo2 Conditioning Resistance in Barley to Host-Specific Subgroups of Magnaporthe oryzae

Phytopathology ◽

10.1094/phyto-09-11-0256 ◽

2012 ◽

Vol 102 (7) ◽

pp. 674-682 ◽

Cited By ~ 7

Author(s):

Nguyen Thi Thanh Nga ◽

Yoshihiro Inoue ◽

Izumi Chuma ◽

Gang-Su Hyon ◽

Kazuma Okada ◽

...

Keyword(s):

Magnaporthe Oryzae ◽

Molecular Mapping ◽

The Other ◽

Avirulence Gene ◽

Barley Cultivar ◽

Avirulence Genes ◽

Genetic Crosses ◽

Barley Cultivars ◽

Genetic Mechanisms ◽

Common Parent

Barley cultivars show various patterns of resistance against isolates of Magnaporthe oryzae and M. grisea. Genetic mechanisms of the resistance of five representative barley cultivars were examined using a highly susceptible barley cultivar, ‘Nigrate’, as a common parent of genetic crosses. The resistance of the five cultivars against Setaria, Oryza, Eleusine, and Triticum isolates of M. oryzae was all attributed to a single locus, designated as Rmo2. Nevertheless, the Rmo2 locus in each cultivar was effective against a different range of isolates. Genetic analyses of pathogenicity suggested that each cultivar carries an allele at the Rmo2 locus that recognizes a different range of avirulence genes. One allele, Rmo2.a, corresponded to PWT1, which conditioned the avirulence of Setaria and Oryza isolates on wheat, in a gene-for-gene manner. The other alleles, Rmo2.b, Rmo2.c, and Rmo2.d, corresponded to more than one avirulence gene. On the other hand, the resistance of those cultivars to another species, M. grisea, was conditioned by another locus, designated as Rmo3. These results suggest that Rmo2 is effective against a broad range of blast isolates but is specific to M. oryzae. Molecular mapping revealed that Rmo2 is located on the 7H chromosome.

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