POLYMORPHISMS IN PHYTOPHTHORA-INFESTANS - 4 MITOCHONDRIAL HAPLOTYPES ARE DETECTED AFTER PCR AMPLIFICATION OF DNA FROM PURE CULTURES OR FROMHOST LESIONS

Four pairs of primers were designed for PCR amplification of known pol ymorphic regions of the mitochondrial genome of Phytophthora infestans , Digestion of the amplified products with restriction enzymes allows identification of previously identified haplotypes, Product P2 cut wit h MspI uniquely identifies haplotypes Ib and IIa, while types Ia and D b are differentiated by digestion of product P4 with EcoRI, Digestion of products P1 and P3 gave results similar to that with digestion of P 4, but amplification of these products was less robust. Thus, all four common haplotypes are identified by amplifying and digesting products P2 and P4. Identification of haplotypes was also possible from DNA ex tracted directly from small, late-blight lesions on both tomato and po tato leaves, making isolation of the fungus unnecessary. A rapid and e fficient method of monitoring changes in the pathogen population is fa cilitated. These: PCR primers were also useful for differentiating oth er Phytophthora species.