Enhancing biological control of postharvest green mold in lemons: Synergistic efficacy of native yeasts with diverse mechanisms of action

Abstract

Argentina is among the most important lemon fruit producers in the world. Penicillium digitatumis the primary lemon fungal phytopathogen, causing green mold during the postharvest.Several alternatives to the use of synthetic fungicides have been developed, being the use ofbiocontrol yeasts one of the most promising. Although many of the reports are based on theuse of a single yeast species, it has been shown that the combination of agents with differentmechanisms of action can increase control efficiency through synergistic effects. The combineduse of native yeasts with different mechanisms of action had not been studied as a biologicalcontrol strategy in lemons. In this work, the mechanisms of action of native yeasts(Clavispora lusitaniae AgL21, Clavispora lusitaniae AgL2 and Clavispora lusitaniae AcL2)with biocontrol activity against P. digitatum were evaluated. Isolate AgL21 was selected for itsability to form biofilm, colonize lemon wounds, and inhibit fungal spore germination. The compatibilityof C. lusitaniae AgL21 with two killer yeasts of the species Kazachstania exigua(AcL4 and AcL8) was evaluated. In vivo assays were then carried out with the yeasts appliedindividually or mixed in equal cell concentrations. AgL21 alone was able to control green moldwith 87.5% efficiency, while individual killer yeasts were significantly less efficient (43.3% and38.3%, respectively). Inhibitory effects were increased when C. lusitaniae AgL21 and K. exiguastrains were jointly applied. The most efficient treatment was the combination of AgL21and AcL4, reaching 100% efficiency in wound protection. The combination of AgL21 withAcL8 was as well promising, with an efficiency of 97.5%. The combined application of nativeyeasts showed a synergistic effect considering that the multiple mechanisms of actioninvolved could hinder the development of green mold in lemon more efficiently than using singleyeasts. Therefore, this work demonstrates that the integration of native yeasts with diversemodes of action can provide new insights to formulate effective microbial consortia. This couldlead to the development of tailor-made biofungicides, allowing control of postharvest fungaldiseases in lemons while remaining competitive with traditionally used synthetic chemicals.