Natural Bacteria from Apples Could Help Fight Apple Ring Rot After Harvest

The study aimed to explore the potential of Bacillus tequilensis QNF2, an endophyte bacterium isolated from Chinese leek (Allium tuberosum) roots, in suppressing the growth of B. dothidea. The researchers conducted both in vitro and in vivo experiments to assess the efficacy of B. tequilensis QNF2 in controlling apple ring rot.

In vitro confront experiments demonstrated that B. tequilensis QNF2 significantly inhibited the mycelial growth of B. dothidea, achieving suppression rates of 73.56% in PDA (Potato Dextrose Agar) medium and 99.5% in PDB (Potato Dextrose Broth) medium. These results indicate the strong antifungal properties of B. tequilensis QNF2 against B. dothidea.

In vivo experiments further validated the biocontrol potential of B. tequilensis QNF2. When postharvest apple fruits were inoculated with B. dothidea and treated with B. tequilensis QNF2, the bacterium exhibited a control efficacy of 88.52% and 100% on ring rot disease, respectively. This remarkable efficacy suggests that B. tequilensis QNF2 could be a viable option for managing apple ring rot during storage.

The study also investigated the mechanisms behind the antifungal activity of B. tequilensis QNF2. The bacterium produced volatile organic compounds (VOCs) that significantly inhibited the mycelial growth of B. dothidea and the development of ring rot on postharvest apples. Additionally, B. tequilensis QNF2 caused severe damage to the mycelial morphology of B. dothidea, further impeding its growth.

Moreover, the research team examined the impact of B. tequilensis QNF2 on the expression of pathogenicity-related genes in B. dothidea. They found that the bacterium significantly repressed the expression of six genes involved in glycolysis and gluconeogenesis pathways, which are critical for the pathogen’s energy production and virulence. This gene repression likely contributes to the reduced pathogenicity of B. dothidea in the presence of B. tequilensis QNF2.

This study builds on previous research highlighting the potential of Bacillus species as biocontrol agents. For instance, Bacillus amyloliquefaciens DHA55 was found to be highly effective in suppressing Fusarium wilt in watermelon by producing antifungal lipopeptides and promoting plant growth^[2]. Similarly, other Bacillus species have shown significant antagonistic activity against various Fusarium species, suggesting their broad-spectrum antifungal properties^[3]. The findings from Qingdao Agricultural University expand the application of Bacillus species to the control of apple ring rot, demonstrating the versatility and efficacy of these biocontrol agents.

In summary, the study conducted by Qingdao Agricultural University provides compelling evidence that Bacillus tequilensis QNF2 is a promising biocontrol agent for managing apple ring rot caused by Botryosphaeria dothidea. By significantly inhibiting the growth of the pathogen and suppressing the expression of its pathogenicity-related genes, B. tequilensis QNF2 offers an environmentally friendly alternative to chemical fungicides. These findings underscore the potential of harnessing beneficial bacteria for sustainable disease management in agriculture.