First report of Phytopythium vexans causing the“Avocado sadness”in Michoacan,Mexico

摘要

Mexico is the main producer,consumer and exporter of avocado in the world,being Michoacan the main producer state contributing more than 80%of the national production.There are phytopathogens that decimate the production causing the death of the tree.Root samples were collected in avocado trees that showed the characteristic symptomatology of the disease known as avocado sadness,the sampling was carried out in four of the main avocado producing towns,in the state of Michoacan,Mexico.The isolation consisted in sowing root tissue in Petri dishes with V8R-PARPH culture medium,subsequently they were identified morphologically and for species level it was determined by molecular biology,with the PCR-ITS technique.Pathogenicity tests were performed in triplicate with avocado seedlings with more than six leaves.After 24 hours,the inoculated plants expressed decay in the apical part,after 120 hours the leaves showed yellowing and after 15 days there was a generalized wilt on the stem and leaves,re-isolating the phytopathogen Phytopythium vexans.This study confirms the first report of the oomycete P.vexans affecting avocado trees in the most important producing region of the Mexican Republic.