AGGRESSIVENESS AND HOST ADAPTATION OF SOME ALGERIAN PHYTOPHTHORA INFESTANS CLONAL LINEAGE ON POTATO AND TOMATO

Abstract

Late blight caused by Phytophthora infestans (Mont.) de Bary is one of the most important biotic constraints to Solanaceae crops.  This investigation was carried out to study host adaptation of some P. infestans  clonal lineages present in Algeria. A total of 36 isolates from different clonal lineages were tested, including EU_23_A1 (n=28), EU_2_A1 (n=3) and EU_13_A2 (n=5), cross inoculation were carried out on potato and tomato leaflets, aggressiveness components such as incubation period, latency period, lesion area and sporangia production were assessed. The results indicated that isolates of EU_23_A1 and EU_2_A1 clonal lineage showed no significant differences in lesion size on both hosts, but sporulated more abundantly on tomato than on potato. However, EU_13_A2 isolates were more aggressive on potato than on tomato, these results suggest that the P. infestans  population in Algeria is subdivided into potato specialist isolates such as the EU_13_A2 lineage, which attacked only potato under field conditions and generalists such as EU_23_A1 and EU_2_A1 lineages which are more adapted to tomato, but attack potato under field conditions. This study is the first in Algeria to identify host adaptation among P. infestans clonal lineages. These data can be useful in developing sustainable control strategies to treat both hosts, especially tomato, which contribute to the production of secondary inoculum in order to reduce the risk of major late blight epidemics.