TY - JOUR
T1 - Concomitant Induction of Systemic Resistance to Pseudomonas syringae pv. lachrymans in Cucumber by Trichoderma asperellum (T-203) and Accumulation of Phytoalexins
AU - Yedidia, Iris
AU - Shoresh, Michal
AU - Kerem, Zohar
AU - Benhamou, Nicole
AU - Kapulnik, Yoram
AU - Chet, Ilan
PY - 2003/12
Y1 - 2003/12
N2 - Most studies on the reduction of disease incidence in soil treated with Trichoderma asperellum have focused on microbial interactions rather than on plant responses. This study presents conclusive evidence for the induction of a systemic response against angular leaf spot of cucumber (Pseudomonas syringae pv. lachrymans) following application of T. asperellum to the root system. To ascertain that T. asperellum was the only micro. organism present in the root milieu, plants were grown in an aseptic hydroponic growth system. Disease symptoms were reduced by as much as 80%, corresponding to a reduction of 2 orders of magnitude in bacterial cell densities in leaves of plants pretreated with T. asperellum. As revealed by electron microscopy, bacterial cell proliferation in these plants was halted. The protection afforded by the biocontrol agent was associated with the accumulation of mRNA of two defense genes: the phenylpropanoid pathway gene encoding phenylalanine ammonia lyase (PAL) and the lipoxygenase pathway gene encoding hydroxyperoxide lyase (HPL). This was further supported by the accumulation of secondary metabolites of a phenolic nature that showed an increase of up to sixfold in inhibition capacity of bacterial growth in vitro. The bulk of the antimicrobial activity was found in the acid-hydrolyzed extract containing the phenolics in their aglycone form. High-performance liquid chromatography analysis of phenolic compounds showed a marked change in their profile in the challenged, preelicited plants relative to that in challenged controls. The results suggest that similar to beneficial rhizobacteria, T. asperellum may activate separate metabolic pathways in cucumber that are involved in plant signaling and biosynthesis, eventually leading to the systemic accumulation of phytoalexins.
AB - Most studies on the reduction of disease incidence in soil treated with Trichoderma asperellum have focused on microbial interactions rather than on plant responses. This study presents conclusive evidence for the induction of a systemic response against angular leaf spot of cucumber (Pseudomonas syringae pv. lachrymans) following application of T. asperellum to the root system. To ascertain that T. asperellum was the only micro. organism present in the root milieu, plants were grown in an aseptic hydroponic growth system. Disease symptoms were reduced by as much as 80%, corresponding to a reduction of 2 orders of magnitude in bacterial cell densities in leaves of plants pretreated with T. asperellum. As revealed by electron microscopy, bacterial cell proliferation in these plants was halted. The protection afforded by the biocontrol agent was associated with the accumulation of mRNA of two defense genes: the phenylpropanoid pathway gene encoding phenylalanine ammonia lyase (PAL) and the lipoxygenase pathway gene encoding hydroxyperoxide lyase (HPL). This was further supported by the accumulation of secondary metabolites of a phenolic nature that showed an increase of up to sixfold in inhibition capacity of bacterial growth in vitro. The bulk of the antimicrobial activity was found in the acid-hydrolyzed extract containing the phenolics in their aglycone form. High-performance liquid chromatography analysis of phenolic compounds showed a marked change in their profile in the challenged, preelicited plants relative to that in challenged controls. The results suggest that similar to beneficial rhizobacteria, T. asperellum may activate separate metabolic pathways in cucumber that are involved in plant signaling and biosynthesis, eventually leading to the systemic accumulation of phytoalexins.
UR - http://www.scopus.com/inward/record.url?scp=2142749057&partnerID=8YFLogxK
U2 - 10.1128/AEM.69.12.7343-7353.2003
DO - 10.1128/AEM.69.12.7343-7353.2003
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
C2 - 14660384
AN - SCOPUS:2142749057
SN - 0099-2240
VL - 69
SP - 7343
EP - 7353
JO - Applied and Environmental Microbiology
JF - Applied and Environmental Microbiology
IS - 12
ER -