Biological control of green mould on mandarin fruit through the combined use of antagonistic yeasts

Penicillium digitatum is the primary cause of green mould in mandarins during the postharvest period, mainly controlled through synthetic fungicides. This study evaluated the biocontrol of green mould on mandarin fruit with three antagonistic yeasts (Hanseniaspora uvarum, Meyerozyma guilliermondii, and Metschnikowia aff. pul-cherrima P01A016), alone or in combination, by elucidating their possible mechanisms of action. All yeast cultures alone (73.85 % -80.64 %) and their combinations (78.40 % -83.18 %) reduced the mycelial growth of green mold in vitro. M. aff. pulcherrima reduced the disease incidence and lesion diameters by 75.5 % and 91.3 %, respectively, demonstrating the highest biocontrolling activity alone. Meyerozyma guilliermondii showed the highest biofilm formation (OD 0.93 +/- 0.01) and antifungal activity (71.13 %) through volatile organic com-pounds (VOCs), while H. uvarum displayed cell-wall degrading beta-1,3 glucanase activity together with mycoci-nogenic and VOCs activity. All tested yeasts showed chitinase, protease, and leucine arylamidase activity. Among dual combinations, M. guilliermondii and M. aff. pulcherrima (M-1) were the most compatible, while M. aff. pulcherrima and H. uvarum (M-3) had the least compatibility. The combined application of these three yeasts resulted in synergistic co-operation, demonstrating the highest biocontrolling efficacy in vitro and in vivo. Inte-grating multiple mechanisms of action in yeasts could create a hurdle approach for inhibiting green mould in citrus as a green alternative to synthetic fungicides. Thus, our study demonstrated that combining biocontrol yeasts can result in beneficial consortia for the eco-friendly and sustainable management of P.digitatum-caused postharvest diseases of mandarins in both the wounded and intact mandarin fruits.

Automated summary

The biocontrol of green mould on mandarin fruit was evaluated using three antagonistic yeasts (Hanseniaspora uvarum, Meyerozyma guilliermondii, and Metschnikowia aff. pul-cherrima P01A016), either alone or in combination. All yeast cultures, alone or in combination, showed inhibitory effects on the mycelial growth of green mould in vitro. Meyerozyma guilliermondii and M. aff. pulcherrima exhibited the highest biocontrol activity, and the combination of these three yeasts showed synergistic cooperation, making it an eco-friendly and sustainable alternative to synthetic fungicides for the management of postharvest diseases in mandarins caused by Penicillium digitatum.