Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

First report of Pythium myriotylum as a causal agent of crown and root rot in soilless green bean cultivation in Italy.

Abstract

In the summer of 2016, during a survey in a commercial greenhouse farm in central Italy (Latium region), over 200 out of 1 000 green bean plants (P. vulgaris cv. Valdarno) showed symptoms of crown and root rot followed by wilting. Plants were cultivated in a pot with sterile perlite and coconut fibre with no recycled-water irrigation system. The infected crowns and roots appeared water soaked with a cinnamon brown colour, and dead plants occurred in distinct and well-delimited areas. Based on morphological features and pathogenicity tests, the causal agent was identified as Pythium myriotylum. The identity was confirmed by cytochrome oxidase subunit 1 and by internal transcribed spacer (ITS) sequence comparison with 100 and 99% homology with HQ708745 and HQ643701, respectively. P. myriotylum is the causal agent of root rot in numerous economically important crops including groundnuts, tomato, wheat, oats, cucumber, soyabean, tobacco and maize. However, only one report described this pathogen on green bean in Europe, namely, in Spain. This is thought to be the first report of P. myriotylum on green bean plants in Italy. A more careful water management in soilless potting mix would avoid the emergence of Pythium root rot in this crop's production system.