Debaryomyces hansenii, Stenotrophomonas rhizophila, and Ulvan as Biocontrol Agents of Fruit Rot Disease in Muskmelon (Cucumis melo L.)

Abstract

The indiscriminate use of synthetic fungicides has led to negative impact to human health and to the environment. Thus, we investigated the effects of postharvest biocontrol treatment with Debaryomyces hansenii, Stenotrophomonas rhizophila, and a polysaccharide ulvan on fruit rot disease, storability, and antioxidant enzyme activity in muskmelon (Cucumis melo L. var. reticulatus). Each fruit was treated with (1) 1 × 106 cells mL−1 of D. hansenii, (2) 1 × 108 CFU mL−1 of S. rhizophila, (3) 5 g L−1 of ulvan, (4) 1 × 106 cells mL−1 of D. hansenii + 1 × 108 CFU mL−1 of S. rhizophila, (5) 1 × 108 CFU mL−1 of S. rhizophila + 5 g L−1 of ulvan, (6) 1 × 106 cells mL−1 of D. hansenii + 1 × 108 CFU mL−1 of S. rhizophila + 5 g L−1 of ulvan, (7) 1000 ppm of benomyl or sterile water (control). The fruits were air-dried for 2 h, and stored at 27 °C ± 1 °C and 85–90% relative humidity. The fruit rot disease was determined by estimating the disease incidence (%) and lesion diameter (mm), and the adhesion capacity of the biocontrol agents was observed via electron microscopy. Phytopathogen inoculation time before and after adding biocontrol agents were also recorded. Furthermore, the storability quality, weight loss (%), firmness (N), total soluble solids (%), and pH were quantified. The antioxidant enzymes including catalase, peroxidase, superoxide dismutase, and phenylalanine ammonium lyase were determined. In conclusion, the mixed treatment containing D. hansenii, S. rhizophila, and ulvan delayed fruit rot disease, preserved fruit quality, and increased antioxidant activity. The combined treatment is a promising and effective biological control method to promote the shelf life of harvested muskmelon.

A Novel Podophage StenR_269 Suggests a New Family in the Class Caudoviricetes

“…Stenotrophomonas rhizophila was first described in 2002 as a rhizobacterium associated with plants and possessing anti-fungal activity [2]. It has been reported that S. rhizophila strains promote root growth and can be used as biocontrol agents [3,4]. Like many other members of the genus, S. rhizophila has high metabolic activity and is able to digest various aromatic compounds, such as phenol, catechol, cresols, benzoic acid, vanillic acid, hydroquinone, and polycyclic pharmaceutical naproxen [1].…”

“…Moreover, it has been shown that the plantassociated strain S. rhizophila DSM14405T (biocontrol agent) possesses unique genes for Viruses 2023, 15, 2437 2 of 13 the synthesis and transport of the plant-protective spermidine, plant cell wall-degrading enzymes, and high salinity tolerance [7,8]. These peculiarities make S. rhizophila a perspective candidate for applications in agriculture and for soil bioremediation [3,4]. Bacteria used as biocontrol agents in agriculture are likely to encounter environmental phages, and those can affect bacterial fitness and characteristics [9].…”

Draft genome sequence of Stenotrophomonas goyisp. nov., a novel bacterium associated with the algaChlamydomonas reinhardtii

“…Finally, some Stenotrophomonas spp. can synthetize useful bioproducts such as antimicrobial and enzymes of biotechnological interest (Rivas-Garcia et al, 2022;Wolf et al, 2002). Here we report the genome of Stenotrophomonas goyi.…”

Stenotrophomonas goyi sp. nov., a novel bacterium associated with the alga Chlamydomonas reinhardtii

“…Finally, some Stenotrophomonas spp. can synthetize useful bioproducts such as antimicrobial and enzymes of biotechnological interest ( Rivas-Garcia et al ., 2022 ; Wolf et al ., 2002 ).…”