Metalaxyl resistance in Phytophthora infestans: An overview

Abstract

Late blight is one of the major destructive diseases of two most important crops –potato and tomato. The disease is known to cause immense loss worldwide. The causal agent Phytophthora infestans, due to various reasons, developed resistance against Metalaxyl fungicide which was very effective against the pathogen, in its initial years of introduction. A number of possibilities have been estimated for the occurrence and development of resistance in the fungal pathogen isolates: existence of resistant isolates before the introduction of the fungicide, development of resistant mutants, presence of both the mating types A1 and A2 of pathogen in a locality leading to the possibilities of recombinants, migration of resistant isolates, excessive use of site specific fungicide etc. Since development of resistance in pathogen population against fungicide is an issue of serious concern and can pose a great threat to the potato and tomato production thus various anti resistance strategies need to be practiced.