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Liu S, Lin G, Ramachandran SR, Daza LC, Cruppe G, Tembo B, Singh PK, Cook D, Pedley KF, Valent B. Rapid mini-chromosome divergence among fungal isolates causing wheat blast outbreaks in Bangladesh and Zambia. New Phytol 2024; 241:1266-1276. [PMID: 37984076 DOI: 10.1111/nph.19402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 10/27/2023] [Indexed: 11/22/2023]
Abstract
The fungal pathogen, Magnaporthe oryzae Triticum pathotype, causing wheat blast disease was first identified in South America and recently spread across continents to South Asia and Africa. Here, we studied the genetic relationship among isolates found on the three continents. Magnaporthe oryzae strains closely related to a South American field isolate B71 were found to have caused the wheat blast outbreaks in South Asia and Africa. Genomic variation among isolates from the three continents was examined using an improved B71 reference genome and whole-genome sequences. We found strong evidence to support that the outbreaks in Bangladesh and Zambia were caused by the introductions of genetically separated isolates, although they were all close to B71 and, therefore, collectively referred to as the B71 branch. In addition, B71 branch strains carried at least one supernumerary mini-chromosome. Genome assembly of a Zambian strain revealed that its mini-chromosome was similar to the B71 mini-chromosome but with a high level of structural variation. Our findings show that while core genomes of the multiple introductions are highly similar, the mini-chromosomes have undergone marked diversification. The maintenance of the mini-chromosome and rapid genomic changes suggest the mini-chromosomes may serve important virulence or niche adaptation roles under diverse environmental conditions.
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Affiliation(s)
- Sanzhen Liu
- Department of Plant Pathology, Kansas State University, Manhattan, KS, 66506-5502, USA
| | - Guifang Lin
- Department of Plant Pathology, Kansas State University, Manhattan, KS, 66506-5502, USA
| | - Sowmya R Ramachandran
- United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Foreign Disease-Weed Science Research Unit, Ft. Detrick, MD, 21702-9253, USA
| | - Lidia Calderon Daza
- Department of Plant Pathology, Kansas State University, Manhattan, KS, 66506-5502, USA
| | - Giovana Cruppe
- Department of Plant Pathology, Kansas State University, Manhattan, KS, 66506-5502, USA
| | - Batiseba Tembo
- Zambia Agricultural Research Institute, Mt. Makulu Central Research Station, Lusaka, 10101, Zambia
| | - Pawan Kumar Singh
- International Maize and Wheat Improvement Center (CIMMYT), Texcoco, 56237, Mexico
| | - David Cook
- Department of Plant Pathology, Kansas State University, Manhattan, KS, 66506-5502, USA
| | - Kerry F Pedley
- United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Foreign Disease-Weed Science Research Unit, Ft. Detrick, MD, 21702-9253, USA
| | - Barbara Valent
- Department of Plant Pathology, Kansas State University, Manhattan, KS, 66506-5502, USA
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