Induced Systemic Resistance Triggered by Clonostachys rosea Against Fusarium circinatum in Pinus radiata

Abstract

Clonostachys rosea (teleomorph Bionectria ochrouleuca) is a powerful biological control agent (BCA), and has been categorized as a broad-spectrum agent against several phytopathogens affecting different crops and forest species. One possible way by which C. rosea can reduce the disease incidence is the Induced Systemic Resistance (ISR), an event associated to several biochemical changes conditioning plants to resist the attack of pathogens. Several studies have found that C. rosea induces resistance against pathogens in legumes, cereals and other crops, but there is a lack of information about the situation in forest species. Therefore, the main goal of this study was to evaluate the behavior of different C. rosea strains as inductors of resistance against the pathogen Fusarium circinatum Niremberg and O`Donnell in two contrasting genotypes of Pinus radiata D. Don. Ten C. rosea strains were applied to the substrate at 8 and 1 days before confronting P. radiata plants with F. circinatum, which was inoculated into 5 μL droplets at a previously cut shoot. The lesion length produced by the pathogen was measured at 60 days post inoculation. It was found that only the resistant P. radiata genotype showed evidence of ISR, with two C. rosea strains, Cr7 and Cr8, triggering resistance and decreasing lesion length to 48.7% and 47.4%, respectively, when compared to pathogen control. These results demonstrate the potential of some C. rosea strains to produce ISR on P. radiata, but at least for this particular pathosystem, this protection appears to be both dependent on the genotype of the host and the inducer C. rosea strain. This is the first report indicating that C. rosea can act as an inducer of resistance on the P. radiate-F. circinatum pathosystem.