Evaluation of Paenibacillus polymyxa carboxymethylcellulose/poly (vinyl alcohol) formulation for control of Carya cathayensis canker caused by Botryosphaeria dothidea

Abstract

Botryosphaeria trunk canker is arguably the most damaging disease of Carya cathayensis (Chinese hickory) in China. Fungicides are commonly applied to control the disease but have serious environmental issues. Here, the Gram‐positive bacterium Paenibacillus polymyxa strain CF05 was evaluated as an alternative for the preventive control of Botryosphaeria trunk canker on C. cathayensis. In vitro, this strain was inhibitory to the growth of B. dothidea, a causal agent of Chinese hickory trunk canker. Formulation of strain CF05 endospores in a carboxymethylcellulose/poly (vinyl alcohol) (CMC/PVA) blend showed high stability over a 12‐month period. A two‐year field experiment suggested that the CMC/PVA formulated strain CF05 reduced the occurrences of both new cankers and established cankers, displaying an efficacy comparable to treatment with thiophanate‐methyl. Furthermore, strain CF05 greatly induced production of phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POX) by C. cathayensis seedlings, which showed maximum activity of these enzymes 2 days postinoculation (dpi) and increased phenol contents inside the trunk throughout the experimental assessment period. In summary, the P. polymyxa strain CF05 CMC/PVA formulation has promise as a potent environmentally friendly agent for the preventive biocontrol of C. cathayensis trunk canker.

Antifungal activity of rapamycin on Botryosphaeria dothidea and its effect against Chinese hickory canker

“…A CMC/PVA formulation used to deliver S. hygroscopicus was prepared as described previously 22 . Briefly, concentrated stock solutions of the CMC (Wealthy Ltd, Changshu, China) and PVA (Wealthy Ltd) were autoclaved separately for 30 min at 121 °C and then diluted into 50 and 10 g L –1 in a container, respectively.…”

“…The incidence of both developed and new cankers was presented as a percentage (i.e. a ratio of the DC and NC counting number vs the total surveyed number) based on the totally surveyed cankers 22 …”

“…8 2.5 Formulation of S. hygroscopicus and its stability A CMC/PVA formulation used to deliver S. hygroscopicus was prepared as described previously. 22 Briefly, concentrated stock solutions of the CMC (Wealthy Ltd, Changshu, China) and PVA (Wealthy Ltd) were autoclaved separately for 30 min at 121°C and then diluted into 50 and 10 g L -1 in a container, respectively. After mixing the final liquid formulations, the culture suspension obtained from the batch fermentation of S. hygroscopicus was added into CMC/PVA (50 and 10 g L -1 , respectively) in equal volumes, resulting in 1.0 × 10 7 coloniesper milliliter.…”

“…20 CMC/PVA blends have been successfully used for film formation and microbial preparation. 21,22 In the present study, we investigated the antifungal activity of rapamycin against B. dothidea and performed a biocontrol assay for an S. hygroscopicus rapamycin-producing strain formulated in CMC/PVA blend. The results of this study could broaden the recognized antifungal spectrum of rapamycin and offer an alternative strategy for the management of Botryosphaeria trunk canker in Chinese hickory.…”

“…Poly(vinyl alcohol) (PVA) is a good candidate for the preparation of hydrogels and has been extensively used for controlling the separations of membrane material or biomaterial 20 . CMC/PVA blends have been successfully used for film formation and microbial preparation 21,22 …”