Biological control of plant pathogens using antagonistic bacteria is a promising strategy and has attracted considerable attention in the efforts

to reduce the use of agricultural chemicals [4]. Endophytic bacteria are those that colonize plant tissues internally without showing any external symptoms or negative effects on their host [5]. Research has shown the potential of endophytic bacteria as biocontrol and plant-growth-promoting agents [6–8]. The Burkholderia cepacia complex (Bcc) is a diverse group of bacteria commonly found in soil, water, and the rhizosphere; on bodies of animal including humans; and in the hospital environment [9]. As endophytic bacteria, members of Bcc have been isolated from a few crops such selleck products as sweet corn, cotton, rice, yellow lupine, and sugarcane [10–13], and B. cepacia strains have proved useful as antagonists of plant pests and in increasing the yield of several crop plants [14–16]. Strain Lu10-1 of B. cepacia (GenBank, EF546394) is an antagonistic endophyte originally isolated from mulberry (Morus alba L.) leaves [17]; however, no attempt has been made to use B. cepacia for controlling C. dematium infection in mulberry nor its colonization patterns have been studied using GFP reporter or other reporters. The objectives of this study were to evaluate the antifungal see more and plant-growth-promoting properties of Lu10-1, to clarify its specific

localization filipin within a mulberry plant, and to better understand its potential as a biocontrol and growth-promoting agent. Results Antifungal activity of strain Lu10-1 against C. dematium in vitro When C. dematium and Lu10-1 bacteria were co-cultured on the same PDA plate, a distinct zone of inhibition was observed around the bacterial inoculum (Fig. 1a). Microscopic observation of the hyphae growing

close to Lu10-1 colonies showed changes in hyphal morphology such as excessive branching, irregular swelling, curling of hyphal tips, and disruption of apical growth. Mycelium from the FHPI order co-cultures showed coagulation of cytoplasm, degradation of the mycelium, and large vesicles inside the cell walls (Fig. 1c). Fig. 2 shows the germination rate of conidia suspended in cell-free culture supernatant fluid (CFCSF), undiluted and in a series of dilutions. No conidia could germinate in suspensions containing CFCSF diluted up to 24-fold; at dilutions higher than that, the inhibitory effect decreased, and ceased altogether when the CFCSF was diluted 96-fold. Figure 1 Burkholdria cepacia strain Lu10-1 antagonism against C. dematium in vitro. a: Interaction between Lu10-1 and C. dematium on a PDA plate. b: Microscopic observation of normal C. dematium mycelium (Bar = 40 μm). c: Microscopic observation of C. dematium mycelium in the zone of interaction with Lu10-1 strains (Bar = 40 μm). Figure 2 Germination rates of C. dematium conidia in dilutions of CFCSF of strain Lu10-1.