ToxA, a significant virulence factor involved in wheat spot blotch disease, exists in the Mexican population of Bipolaris sorokiniana


Spot blotch, caused by the pathogen Bipolaris sorokiniana, is an important foliar disease of wheat in warm and humid regions worldwide. The fungal virulence factor ToxA interacts with Tsn1 in wheat and leads to a susceptible reaction. ToxA has been found in B. sorokiniana populations of Australia, the USA, and India, and here we report its occurrence in Mexico, based on analysis of a collection of 196 Mexican isolates of B. sorokiniana. The isolates were collected from experimental stations and farmers’ fields in nine states of Mexico, during the period from 1992 to 2017. A PCR assay with the ToxA-specific marker was conducted, and the results revealed the presence of ToxA in 20 isolates (10.2%). Culture filtrate infiltration experiments confirmed that all the 20 isolates were able to induce necrosis reaction on Glenlea, a wheat genotype with Tsn1. This is the first report on the occurrence of ToxA in Mexican B. sorokiniana population, which is key information for breeding wheat for resistance against spot blotch.

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The authors would like to express their gratitude to Drs. Etienne Duveiller, Monica Mezzalama, Karim Ammar, and Julio Huerta, CIMMYT, for their contribution in the collection of B. sorokiniana isolates. Technical supports from Maria Elena Lemus, Monica Preciado, Javier Segura, and Francisco Lopez are highly acknowledged.


The authors received financial support through the CGIAR Research Program on WHEAT, National Natural Science Foundation of China (31561143004) and Natural Science Foundation of Jiangsu Province, China (BK20170609).

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PS and XH conceived and designed the experiments; LW and NL performed the experiments; LW, XH, and XZ analyzed the data; LW and XH wrote the paper, and all coauthors approved the final version of the manuscript.

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Correspondence to Pawan K. Singh.

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Wu, L., He, X., Lozano, N. et al. ToxA, a significant virulence factor involved in wheat spot blotch disease, exists in the Mexican population of Bipolaris sorokiniana. Trop. plant pathol. 46, 201–206 (2021).

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  • Cochliobolus sativus
  • PCR
  • Disease resistance
  • Triticum aestivum
  • Tsn1