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First Report of Haplotype I-b of Phytophthora infestans in Central Mexico
E Garay-Serrano1, S P Fernández-Pavía1, G Rodríguez-Alvarado1
1Instituto de Investigaciones Agropecuarias y Forestales, UMSNH, Tarímbaro, Michoacán, México.
Abstract:
Central Mexico is considered a center of genetic diversity for Phytophthora infestans on the basis of a range of genotypic and phenotypic characteristics (3). Surprisingly, while mitochondrial DNA (mtDNA) haplotypes I-a, II-a, and II-b have been reported from central Mexico, haplotype I-b has not been found in central Mexico (1). Therefore, a more extensive search for haplotypes was conducted in areas where sexual reproduction occurs. During the summer of 2003, leaflets of cvs. Rosita and Tollocan with a single lesion of late blight were collected in the area of Villarreal, located in Terrenate County in Tlaxcala, Mexico (170 km northeast of Mexico City). Fourteen P. infestans isolates were characterized for mtDNA haplotype, isozyme genotype (glucose 6- phosphate isomerase [Gpi] and peptidase [Pep]), and mating type. Isolation, mating type, and isozyme genotype were characterized following reported protocols (1,4). MtDNA haplotype was determined by amplifying and digesting the P2 and P4 regions and comparing amplicons to those of reference strains of known haplotype (1,2). Twelve isolates were mtDNA haplotype I-a and two were I-b. While the mtDNA I-b has been associated with the US-1 lineage (mating type: A1, Gpi: 86/100, Pep: 92/100), the genotypes for the Mexican isolates were A2, 86/100 Gpi, 100/100 Pep from cv. Rosita and A2, 86/100 Gpi, 92/100 Pep from cv. Tollocan. To our knowledge, this is the first report of the I-b mtDNA haplotype of P. infestans from central Mexico and it is now clear that all four haplotypes exist in Mexico. This finding therefore, stresses the importance of including a representative regional sampling of Mexican and Andean isolates in studies inferring the origin of this species. References: (1) W. G. Flier et al. Phytopathology 93:382, 2003. (2) G. W. Griffith and D. S. Shaw. Appl. Environ. Microbiol. 64:4007, 1998. (3) N. J. Grünwald and W. G. Flier. Ann. Rev. Phytopathol. 43:171, 2005. (4) N. J. Grünwald et al. Phytopathology 91:882, 2001.
Insights
The first report of Phytophthora infestans mitochondrial DNA haplotype I-b in central Mexico confirms all four haplotypes exist there. This finding is crucial for understanding the pathogen
Area of Science:
- Plant Pathology
- Molecular Genetics
- Microbial Ecology
Background:
- Central Mexico is recognized as a significant center for Phytophthora infestans genetic diversity.
- Previous studies reported mitochondrial DNA (mtDNA) haplotypes I-a, II-a, and II-b in central Mexico, but notably excluded haplotype I-b.
- The absence of haplotype I-b prompted further investigation in regions conducive to sexual reproduction.
Purpose of the Study:
- To conduct an extensive search for mitochondrial DNA (mtDNA) haplotypes of Phytophthora infestans in central Mexico.
- To characterize isolates for mtDNA haplotype, isozyme genotype, and mating type.
- To determine the complete distribution of P. infestans mtDNA haplotypes in central Mexico.
Main Methods:
- Collection of Phytophthora infestans isolates from infected potato leaflets (cvs. Rosita and Tollocan) in Tlaxcala, Mexico.
- Characterization of isolates using established protocols for isolation, mating type, and isozyme genotype (glucose 6-phosphate isomerase [Gpi] and peptidase [Pep]).
- Determination of mtDNA haplotype by amplifying and digesting specific DNA regions (P2 and P4) and comparing to reference strains.
Main Results:
- Out of fourteen P. infestans isolates analyzed, twelve were identified as mtDNA haplotype I-a and two as haplotype I-b.
- The two I-b haplotype isolates from central Mexico exhibited distinct genotypes (A2 mating type, 86/100 Gpi, 100/100 Pep and A2 mating type, 86/100 Gpi, 92/100 Pep) compared to the US-1 lineage.
- This study provides the first documented evidence of the P. infestans I-b mtDNA haplotype in central Mexico.
Conclusions:
- The presence of all four major mitochondrial DNA (mtDNA) haplotypes (I-a, I-b, II-a, II-b) is now confirmed in central Mexico.
- The discovery of haplotype I-b in this region highlights the importance of comprehensive regional sampling in genetic diversity studies.
- Future research on the origin and evolution of Phytophthora infestans should include representative Mexican and Andean isolates.
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