Identification, distribution and functional diversity of Iranian isolates of Pythium oligandrum

Pythium oligandrum is known as an important biological agent against plant pathogens. Isolates from different regions of Iran including Bushehr, Bakhtiari, Chaharmahal, Fars, Golestan, Ilam, Kermanshah, Kerman, West Azerbaijan and Yazd were identified based on morphological and molecular characteristics. The highest recovering frequency of isolates was observed in Kermanshah and Fars provinces. The functional diversity of isolates based on their growth temperature and biological control effect under laboratory conditions was evaluated. The antagonistic effects of native P. oligandrum isolates were evaluated against soil–borne fungal pathogens including Rhizoctonia solani, Phytophthora parasitica, Fusarium solani, F. oxysporum f. sp. lycopersici and F. oxysporum f. sp. pisi using nonparametric statistics, and compered with commercial products of various biocontrol agents such as Clonostachys rosea, Fusarium oxysporum, P. oligandrum and Trichoderma spp. The native isolates of P. oligandrum were diverse in their growth temperature and biocontrol activities. The highest mycelial growth inhibition was found in the interaction between P. oligandrum isolates and R. solani. A significant difference between P. oligandrum isolates was found by evaluating their volatile compounds. The isolates of P. oligandrum showed maximum inhibition on P. parasitica and R. solani and minimum inhibition on F. oxysporum f. sp. lycopersici. The non–volatile compounds had the highest significant effect on P. parasitica as well. The result of this study showed that the growth characteristics and the in vitro biocontrol ability of the native isolates of P. oligandrum on various plant pathogens were different. This variety can be employed in biochemical and greenhouse screening of the isolates.