DIVERSIDAD GENÉTICA DEL TIZÓN TARDÍO DE LA PAPA (Phytophthora infestans (Mont) de Bary) EN CHAPINGO, MÉXICO GENETIC DIVERSITY OF POTATO LATE BLIGHT (Phytophthora infestans (Mont) de Bary) AT CHAPINGO, MÉXICO

In the Mexican central highlands, late blight (Phytophthora infestans) has high incidence, severity and genotypic diversity, due in part to its sexually derived progeny. The objective of this study was to evaluate the mating type, allozyme profile and mitochondrial haplotype of 88 isolates of P. infestans obtained from simple random lesions of potato clones at the experimental agricultural station of the University of Chapingo, Mexico, in 2008, 2009 and 2010. Homothallic population (A1/A2) predominated, with a frequency of 0.761. A1 and A2 frequencies were 0.125 and 0.114, respectively. Twenty five allozyme genotypes were identified, with alleles 100 and 122 for peptidase (Pep), and 86, 90, 100, 111 and 122 for glucose phosphate isomerase (Gpi). The most common genotype was A1/A2, Pep 100/100 and Gpi 86/100 (frequency 0.216). The genotypic diversity index was 1.8 and only the Ia mitochondrial haplotype was identified. Few genotypes could be located accurately in any of the existing classifications, so they are considered unique in the area or not present in other regions. For their genetic diversity a broader classification is needed, including most of multilocus alleles detected by alloenzymes and homothallic condition.