Competitive saprophytic ability of the hypovirulent isolate QT5-19 of Botrytis cinerea and its importance in biocontrol of necrotrophic fungal pathogens

Abstract

This study determined the competitive saprophytic ability (CSA) of the hypovirulent isolate QT5-19 of Botrytis cinerea on potato dextrose agar (PDA) at 20 °C. Meanwhile, importance of the QT5-19 CSA in biocontrol against virulent isolates of B. cinerea and Sclerotinia sclerotiorum (a close relative of B. cinerea), and the mechanisms for the QT5-19 CSA were elucidated. The results showed that QT5-19 had higher CSA than the virulent isolates 08168 (B. cinerea) and EP-1PNA367 (S. sclerotiorum) on potato dextrose agar. The hyphal fragments of QT5-19 exhibited an effective suppression against infection of leaves of oilseed rape by the hyphae of the two virulent fungal pathogens through competition. QT5-19 was detected to be able to produce volatile organic compounds (VOCs) with antifungal activity against B. cinerea and S. sclerotiorum, whereas the VOCs from the virulent isolate RoseBc-3 of B. cinerea had no detectable antifungal activity. The QT5-19 VOCs effectively reduced disease severity of strawberry fruit rot caused by two virulent fungal pathogens. These results suggest that QT5-19 may achieve success of competition through extensive mycelial growth and production of antifungal volatiles. This study provided an example of using hypovirulent isolates to control virulent isolates of B. cinerea and S. sclerotiorum.