Enhancement of defence responses against Bayoud disease by treatment of date palm seedlings with an hypoaggressive Fusarium oxysporum isolate

Pretreatment of date palm seedlings with an hypoaggressive Fusarium isolate (AHD) protected them partially from further infection by Fusarium oxysporum f.sp. albedinis (Foa), the Bayoud disease pathogen. No mortality occurred during 2-3 months of incubation in plants pretreated with AHD, as opposed to aggressive isolate (ZAG) inoculated controls where up to 100% mortality was observed 15-30 days after inoculation. Such protection involved biochemical interactions between the host plant and AHD since no direct competition or antagonism was revealed between AHD and ZAG. The examination of the accumulation of phenolics and peroxidase activity, two parameters previously reported to be involved in date palm resistance to Foa, indicated that the response to AHD was correlated with the ability of pretreated date palm tissues to establish a faster defence response in the roots of both susceptible and resistant cultivars. Plants pretreated with AHD accumulated higher amounts of phenolics, mainly non-constitutive hydroxycinnamic acid derivatives, which play a crucial role in date palm defence against Foa, as previously described by our group. These compounds were accumulated along with the constitutive caffeoylshikimic acids. A faster induction of peroxidase activity in response to Foa was also recorded in plants pretreated with AHD. Given the multi-component nature of these induced responses, AHD could be part of integrated disease management strategies for a sustainable control of the palm tree Bayoud disease.