Volatile Organic Compounds Produced by Pseudomonas chlororaphis subsp. aureofaciens SPS-41 as Biological Fumigants To Control Ceratocystis fimbriata in Postharvest Sweet Potatoes

Abstract

The biocontrol activity and chemical composition of the volatile organic compounds (VOCs) produced by Pseudomonas chlororaphis subsp. aureofaciens SPS-41 were investigated. The VOCs inhibited mycelial growth and spore germination in Ceratocystis fimbriata, which causes black rot disease in sweet potato tuber roots (TRs) and showed wide-spectrum antifungal activity against several plant pathogenic fungi. A microscopic examination of C. fimbriata cells suggested morphological changes and a loss of cellular contents. Different inoculation strategies significantly affected the antifungal activity of the VOCs. In the volatile profile of SPS-41, the most abundant compound, 3-methyl-1-butanol, followed by phenylethyl alcohol and 2-methyl-1-butanol showed strong inhibition toward C. fimbriata. The weight loss rate and disease severity of the TRs were significantly reduced in response to the VOCs emitted by SPS-41. The results suggest that the VOCs produced by P. chlororaphis subsp. aureofaciens SPS-41 might constitute an attractive biological fumigant for controlling black rot disease in sweet potato TRs.

Identification of Rhizospheric Actinomycete Streptomyces lavendulae SPS-33 and the Inhibitory Effect of its Volatile Organic Compounds against Ceratocystis fimbriata in Postharvest Sweet Potato (Ipomoea batatas (L.) Lam.)

“…These three volatiles have good antimicrobial activity and can be produced by a variety of microorganisms, such as S. fimicarius BWL-H1, different Actinobacteria isolates, and Pseudomonas chlororaphis subsp. aureofaciens SPS-41 [20,49,50]. It was found that alcohols showed a noticeably higher antimicrobial activity than esters and ketones in this study, which was consistent with other reports [9,20].…”

“…The antagonistic assay of VOCs produced by SPS-33 against C. fimbriata was determined according to the previous research [20] with minor modifications. Potato dextrose agar (PDA) medium was added to one side of the I-plates (diameter, 90 mm, volume, 0.07 L), and ISP 2 medium was added to the other side of the same plate.…”

“…Meanwhile, the sporulation capacity was counted every day with a hemocytometer. Mycelial morphology was observed after dyeing with lactophenol cotton blue [20].…”

“…Evaluation of disease severity (DS) was based on a five-degree empirical scale: (1) 0 mm < lesion diameter ≤ 8 mm, (2) 8 mm < lesion diameter ≤ 16 mm, (3) 16 mm < lesion diameter ≤ 24 mm, (4) 24 mm < lesion diameter ≤ 32 mm, and (5) 32 mm < lesion diameter ≤ 40 mm. DS was calculated according to the formulas in the literature [20].…”

“…The GC-MS analyses were determined by the Agilent 7890B GC system and Agilent 5975C mass spectrometer. The GC-MS condition used for analysis was as mentioned according to the method described by Zhang et al [20]. The Chroma TOF 4.3X software (LECO Corporation) was used for peaks extraction, filtering and calibration, and VOCs produced by strain SPS-33 were tentatively identified by the National Institute of Standards and Technology (NIST 14) database.…”