The colonization pattern was similar to that observed for many other endophytes [19–22]. Several mechanisms of disease suppression have been proposed, such as antibiotic metabolites
production, siderophore production, and induction of systemic resistance . It was reported that induced systemic resistance (ISR) might be one of the most important operating mechanisms of disease suppression [24, 25]. Many investigators have shown that ISR is triggered by bacterial inoculation [26–29]. Our results demonstrate that Lu10-1 is an effective biocontrol agent against anthracnose of mulberry in a greenhouse although JSH-23 concentration the extent of disease suppression varied with the length of the gap between application of the bacterial strain and inoculation with the pathogen (Fig. 3). Although strain Lu10-1 could multiply and spread inside mulberry plants, we could not re-isolate Lu10-1 from the leaves inoculated with C. dematium pathogen within 3 days of applying the bacteria either to the soil or uninoculatd leaves. This rules out any physical contact between the bacteria and the pathogen on the leaf surfaces, and yet the plants showed resistance to C. dematium
at sites distant from the site of application of Lu10-1. We therefore attribute the disease suppression to resistance induced in the mulberry plant, which might be one of the mechanisms underlying biocontrol by Lu10-1. It was reported that bacterial populations must be of certain minimum size before they can induce such resistance . Therefore, some time must elapse between the application of the bacteria and inoculation with C. dematium PRN1371 for the bacteria to build up their population to the level necessary for colonizing plant tissues–which is why the extent of disease suppression
varied with the length of the interval between the application of Lu10-1 and inoculation with the pathogen. Though the disease was not suppressed when the treatment and the inoculation were simultaneous but the sites of the two interventions GNA12 were separated in space, it was suppressed significantly when the bacteria were applied to the same site, that is to the inoculated leaves. Furthermore, we found that Lu10-1 produces a metabolite that is released into the medium and inhibits mycelial growth (Fig. 1a) and conidial germination (Fig. 2) in C. dematium. Our results show that Lu10-1 can produce bacterial siderophores, which are low-molecular-weight compounds that can inhibit the growth of plant pathogens. These Cediranib siderophores might also be partly responsible for the biocontrolling properties of Lu10-1. Thus Lu10-1 apparently has multiple mechanisms of antifungal activity that protect mulberry under greenhouse conditions against leaf infection by C. dematium. Genetic and biochemical studies will be conducted to determine the exact mechanisms that are essential to the biocontrol potential of strain Lu10-1.