Knowledge of the ecology of biological control agents (BCAs), previously reported to be effective against the citrus vascular pathogen Plenodomus tracheiphilus, is required to improve scheduling of BCA field applications. Culture-dependent methods (dilution plate and direct plating) and culture-independent qPCR assays were used to determine survival of Bacillus amyloliquefaciens QST 713 and Trichoderma asperel lum ICC 012 + T. gamsii ICC 080 on citrus stem and leaf tissues following foliar applications, and root endospheres and rhizospheres following root drenches with these Trichoderma BCAs. Viable population levels of B. amyloliquefaciens did not change over time on treated stems, whereas these decreased in leaf samples after 14 d. The qPCR assay detected B. amyloliquefaciens in all collected samples, with no temporal changes in population levels. Although the qPCR assay detected T. asperellum and T. gamsii in leaf and stem tissues, these fungi were isolated only from stem tissues, with increased isolations at 21 d post treatment compared with 7 d. Neither qPCR nor culturing detected Trichoderma species in citrus vascular root tissues. However, qPCR and culturing detected these fungi in host rhizospheres at 7, 14 and 21 d post inoculation, confirming their rhizosphere competence. This study has provided insights into colonization and survival within citrus plants of B. amyloliquefaciens and T. asperellum + T. gamsii contained in commercial biocontrol products. These indicate that integrating qPCR and culture-dependent approaches is important for detecting and quantifying these BCAs. The endophytic lifestyle of B. amyloliquefaciens and T. asperellum + T. gamsii makes them likely to provide long-term biological control. These results also indicate that the selected Bacillus and Trichoderma agents could spread and colonize citrus tissues over extended periods, and especially after host pruning or damage, which could promote plant colonization and protection from pathogens.
Detection and persistence of Bacillus and Trichoderma-based biocontrol products on lemon plants
Leonardi G. R.;Vaccalluzzo A.;Gusella G.
;La Quatra G.;Pino A.;Aiello D.;Caggia C.;Randazzo C. L.;Polizzi G.
2026-01-01
Abstract
Knowledge of the ecology of biological control agents (BCAs), previously reported to be effective against the citrus vascular pathogen Plenodomus tracheiphilus, is required to improve scheduling of BCA field applications. Culture-dependent methods (dilution plate and direct plating) and culture-independent qPCR assays were used to determine survival of Bacillus amyloliquefaciens QST 713 and Trichoderma asperel lum ICC 012 + T. gamsii ICC 080 on citrus stem and leaf tissues following foliar applications, and root endospheres and rhizospheres following root drenches with these Trichoderma BCAs. Viable population levels of B. amyloliquefaciens did not change over time on treated stems, whereas these decreased in leaf samples after 14 d. The qPCR assay detected B. amyloliquefaciens in all collected samples, with no temporal changes in population levels. Although the qPCR assay detected T. asperellum and T. gamsii in leaf and stem tissues, these fungi were isolated only from stem tissues, with increased isolations at 21 d post treatment compared with 7 d. Neither qPCR nor culturing detected Trichoderma species in citrus vascular root tissues. However, qPCR and culturing detected these fungi in host rhizospheres at 7, 14 and 21 d post inoculation, confirming their rhizosphere competence. This study has provided insights into colonization and survival within citrus plants of B. amyloliquefaciens and T. asperellum + T. gamsii contained in commercial biocontrol products. These indicate that integrating qPCR and culture-dependent approaches is important for detecting and quantifying these BCAs. The endophytic lifestyle of B. amyloliquefaciens and T. asperellum + T. gamsii makes them likely to provide long-term biological control. These results also indicate that the selected Bacillus and Trichoderma agents could spread and colonize citrus tissues over extended periods, and especially after host pruning or damage, which could promote plant colonization and protection from pathogens.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
