Genotypic Characterization of Phytophthora infestans from Mauritius using Random Amplified Polymorphic DNA (RAPD), Mitochondrial Haplotyping and Mating Type Analysis

摘要

Background and Objective: Control of late blight disease of potato and tomato, caused by the oomycete Phytophthora infestans ( P. infestans ), remains a highly challenging task in almost all potato and tomato growing areas around the world. This is partly due to the high degree of polymorphism in this pathogen?s genome, which has been reported to rapidly evolve via host jumps followed by specialization. Late blight remains a major problem in Mauritius where fungicide use is less common on potato and certified seed programs are not well established. This study aimed at investigating the genetic identity of P. infestans isolates in Mauritius collected during the late blight seasons from 2012-2014 using mitochondrial haplotyping, PCR-based mating type analysis and random amplified polymorphic DNA (RAPD). Materials and Methods: Seven isolates were collected from distinct geographical areas around the island, cultured by baiting with potato disks and subsequently isolated on antibiotic-amended pea agar for further analysis. Mitochondrial haplotyping was carried out using four previously characterized polymorphic regions of the mitochondrial genome, mating type analysis was carried out using a CAPS assay and RAPD fingerprinting was carried out using 40 random oligomers. Results: All of the isolates were shown to belong to mitochondrial type II and mating type A2 and no A1 mating type was detected. Codified data from RAPD fingerprinting was used to construct a consensus dendogram using the UPGMA method, which grouped isolates into 3 distinct clusters but all isolates were shown to be genetically distinct from each other and there was no indication of geographical clustering. Conclusion: These results reveals a much wider diversity among the existing populations of P. infestans found on the island than was previously thought. It infers that blight isolates may be gaining access to the island from several different geographical sources and underlines the importance of stricter screening procedures on imported seed potato and tomato being imported onto the island.