Abstract
Botryosphaeria dothidea causes apple ring rot, which is among the most prevalent postharvest diseases of apples and causes significant economic loss during storage. In this study, we investigated the biocontrol activity and possible mechanism of Bacillus velezensis strain P2-1 isolated from apple branches against B. dothidea in postharvest apple fruit. The results showed strain P2-1, one of the 80 different endophytic bacterial strains from apple branches, exhibited strong inhibitory effects against B. dothidea growth and resulted in hyphal deformity. B. velezensis P2-1 treatment significantly reduced the ring rot caused by B. dothidea. Additionally, the supernatant of strain P2-1 exhibited antifungal activity against B. dothidea. Re-isolation assay indicated the capability of strain P2-1 to colonize and survive in apple fruit. PCR and qRT-PCR assays revealed that strain P2-1 harbored the gene clusters required for biosynthesis of antifungal lipopeptides and polyketides. Strain P2-1 treatment significantly enhanced the expression levels of pathogenesis-related genes (MdPR1 and MdPR5) but did not significantly affect apple fruit qualities (measured in fruit firmness, titratable acid, ascorbic acid, and soluble sugar). Thus, our results suggest that B. velezensis strain P2-1 is a biocontrol agent against B. dothidea-induced apple postharvest decay. It acts partially by inhibiting mycelial growth of B. dothidea, secreting antifungal substances, and inducing apple defense responses.
Highlights
Apple ring rot, caused by Botryosphaeria dothidea, is one of the most prevalent postharvest diseases affecting apples
Strain P2-1 cell suspension dramatically reduced the incidence of disease and average lesion width in apple fruits, infected with Bd7 isolate (Figure 5). These findings revealed that strain P2-1 was capable of suppressing apple ring rot disease caused by the carbendazimresistance isolate
We demonstrated that the use of B. velezensis strain P21 effectively reduced the width of apple ring rot lesions and the incidence of postharvest disease caused by B. dothidea, implying that this strain constitutes a promising resource for biocontrol of B. dothidea caused apple postharvest decay
Summary
Apple ring rot, caused by Botryosphaeria dothidea, is one of the most prevalent postharvest diseases affecting apples. It results in significant yield and quality losses during storage (Tang et al, 2012; Jurick et al, 2013; Zhang et al, 2016; Huang et al, 2021). Apple ring rot caused by B. dothidea is difficult to control due to the latent infection characteristic (Liu et al, 2011). This disease is primarily controlled through the use of fungicides but environmental and food safety concerns severely limit their use. Alternative and environmentally friendly methods of controlling this disease are urgently needed
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