Streptomyces albidoflavus Strain CARA17 as a Biocontrol Agent against Fungal Soil-Borne Pathogens of Fennel Plants

Abstract

Fennel crop is a horticultural plant susceptible to several soil-borne fungal pathogens responsible for yield losses. The control of fungal diseases occurring on fennel crops is very difficult with conventional and/or integrated means; although several chemical fungicides are able to contain specific fungal diseases, they are not registered for fennel crops. The intensive use of some fungicides causes public concern over the environment and human health. The main aims of this study were to assess the ability of a strain of Streptomyces albidoflavus CARA17 to inhibit the growth of fungal soil-borne pathogens, and to protect fennel plants against severe fungal soil-borne pathogens such as Athelia rolfsii, Fusarium oxysporum, Plectosphaerella ramiseptata, Sclerotinia sclerotiorum and Verticillium dahliae. This study confirmed that the CARA17 strain has been able to inhibit the mycelium growth of pathogens in vitro conditions with significant inhibition degrees, where S. sclerotiorum resulted in being the most controlled. The strain CARA17 was also able to significantly protect the fennel seedlings against fungal soil-borne pathogens used in vivo conditions, where the treatment with an antagonist strain by dipping resulted in being more effective at limiting the disease severity of each fungal soil-borne pathogen. Moreover, any treatment with the CARA17 strain, carried out by dipping or after transplanting, produced benefits for the biomass of fennel seedlings, showing significant effects as a promoter of plant growth. Finally, the results obtained showed that CARA17 is a valid strain as a biocontrol agent (BCA) against relevant fungal soil-borne pathogens, although further studies are recommended to confirm these preliminary results. Finally, this study allowed for first time worldwide the association of Plectosphaerella ramiseptata with fennel plants as a severe pathogen.

Biological Control of Severe Fungal Phytopathogens by Streptomyces albidoflavus Strain CARA17 and Its Bioactive Crude Extracts on Lettuce Plants

“…The identification and characterization of fungal phytopathogens and CARA17 strain, as well as the antagonistic activity in dual culture were ascertained as reported in previous research [ 15 ]. Regarding the antagonistic activity played by the culture filtrate of the CARA17 strain, the results are reported in Table 1 .…”

“…against several phytopathogens [ 14 ]. It is known that actinomycetes are extensively present micro-organisms in the environment that have potential to produce bioactive compounds against phytopathogens [ 15 , 16 ]. Among the actinomycetes, Streptomyces is the largest genus belonging to the family Streptomycetaceae [ 17 ], with interesting potential to produce compounds for antibiotics and agro-antibiotics, or other bioactive compounds [ 18 , 19 , 20 ].…”

“…Although a few studies have been carried out to assess the biocontrol efficacy and mechanism of Streptomyces spp. [ 15 , 17 ], to date, there has been no research related to the control of soilborne pathogens on lettuce crops.…”

Chitosan and Trichoderma harzianum a new Challenge for managing Fusarium crown and root rot in asparagus plant

“…Nowadays, alternative control methods without using fungicides, mainly on chemical-synthetic origin, that can be harmful to human health and the environment are considered (du et al 2022). Numerous studies have been published about the ability of eco-friendly agents to control soil-borne fungal pathogens in different crops (Carlucci et al 2022;Gao et al 2022;Viejobueno et al 2021), however there are few studies based on biological agents to control fusarium crown and root rot in asparagus plant, as far as we know (elmer 2015;farahani-Kofoet et al 2020).…”

Two cyanobacteria culture filtrates as potential biocides for controlling damping-off and root-rot diseases of fennel plants

“…and Sclerotium rolfsii, stem-rot by Sclerotinia sclerotiorum) and Fusarium wilt (Fusarium oxysporum f.sp. funiculi) are the common and most serious diseases of fennel in Egypt and in the world [3,4,5]. Damping-off and root rot causes seeds, seedling death at early to late stage resulting in very poor plant stand which ultimately produces very low yield [6,7,5].…”