Genetic polymorphism of ToxB+ Pyrenophora tritici-repentis strains

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BACKGROUND: The phytotoxin Ptr ToxB as well as Ptr ToxA is one of the pathogenic factors of Pyrenophora tritici-repentis, that cause leaf chlorosis on susceptible wheat varieties, and is encoded by ToxB gene. P. tritici-repentis strains with ToxB gene are rather rare worldwide.

MATERIALS AND METHODS: The object of the study was 37 strains isolated from the leaves of wheat grown in Greece. The virulence of the strains was analyzed and the presence of effector genes as well as the average copy number of ToxB was determined.

RESULTS: The race composition of P. tritici-repentis population turned out to be mainly represented by the avirulent race 4 (50% of the strains). Strains of race 1 were not found, while strains of other races were found with a low frequency in the population. All analyzed P. tritici-repentis strains had ToxB gene in the genome, while its homologues and ToxA gene were not detected. The average copy number (R) of ToxB in three P. tritici-repentis strains varied from 0.24 to 1.22. The average copy number of ToxB in the mitotic generation of P. tritici-repentis Gr8 strain, which was characterized by the lowest value of R = 0.24, varied from 0.01 to 0.74 and, on average, turned out to be 2 times higher than in the original strain Gr8.

CONCLUSION: Presumably, P. tritici-repentis has a mechanism that gives ToxB+ nuclei an advantage in the division rate over ToxB nuclei. This mechanism indicates the existence of an additional function of this gene that is not associated with pathogenicity.

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About the authors

Nina V. Mironenko

All-Russian institute of plant protection

Author for correspondence.
ORCID iD: 0000-0003-3383-2973
SPIN-code: 2047-7349

Dr. Sci. (Biol.)

Russian Federation, 3 Podbelsky highway, Saint Petersburg, Pushkin, 196608

Aleksandra S. Orina

All-Russian institute of plant protection

ORCID iD: 0000-0002-7657-6618
SPIN-code: 8590-0092

PhD, Cand. Sci. (Biol.)

Russian Federation, 3 Podbelsky highway, Saint Petersburg, Pushkin, 196608

Nadezhda M. Kovalenko

All-Russian institute of plant protection

ORCID iD: 0000-0001-9577-8816
SPIN-code: 9610-4614

PhD, Cand. Sci. (Biol.)

Russian Federation, 3 Podbelsky highway, Saint Petersburg, Pushkin, 196608


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Supplementary files

Supplementary Files
1. Fig. 1. The race composition of P. tritici-repentis population from Greece

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2. Fig. 2. The average copy number of ToxB gene in subclones of the strain P. tritici-repentis Gr8. The line shows average copy number of ToxB in the original strain

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