Developing <i>Penicillium digitatum</i> Management Strategies on Post-Harvest Citrus Fruits with Metabolic Components and Colonization of <i>Bacillus subtilis</i> L1-21
2022
Yongmei Li | Mengyuan Xia | Pengbo He | Qiaoming Yang | Yixin Wu | Pengfei He | Ayesha Ahmed | Xiangsong Li | Yuehu Wang | Shahzad Munir | Yueqiu He
Citrus is among the most important plants in the fruit industry severely infected with pathogens. Citrus green mold caused by <i>Penicillium digitatum</i> is one of the most devastating diseases during post-harvest stages of citrus fruit. In this study, a potential endophyte <i>Bacillus subtilis</i> L1-21, isolated from healthy citrus plants, was assessed for its biocontrol activity against the pathogen <i>P. digitatum</i>. Based on an in vitro crosstalk assay, we suggested that <i>B. subtilis</i> L1-21 inhibits the pathogen with an inhibition zone of 3.51 ± 0.08 cm. Biocontrol efficacy was highest for the fermented culture filtrate of <i>B. subtilis</i> L1-21. Additionally, using GC-MS analysis, 13 compounds were detected in the extract of this endophyte. The culture filtrate in Landy medium could enlarge and deform pathogen spores and prevent them from developing into normal mycelium. Accordingly, the Landy culture filtrate of <i>B. subtilis</i> L1-21 was stable in the temperature range of 4–90 °C and pH of 3–11. Further, MALDI-TOF-MS for <i>B. subtilis</i> L1-21 detected surfactin, fengycin, bacillaene and bacilysin as potential antifungal compounds. GFP-tagged <i>B. subtilis</i> L1-21 easily colonized in citrus fruit peel and pulp, suggesting its role in eliminating the fungal pathogen. Altogether, it is highly expected that the production of antifungal compounds, and the colonization potential of <i>B. subtilis</i> L1-21 are required against the post-harvest <i>P. digitatum</i> pathogen on citrus fruit.
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