The influence of growth conditions on biomass, toxins and pathogenicity of Fusarium oxysporum f. sp. orthoceras, a potential agent for broomrape biocontrol

Abstract

The influence of different combinations of illumination and shaking on the growth dynamics, pathogenicity and toxin production of the fungus Fusarium oxysporum f. sp. orthoceras, a biocontrol agent of Orobanche cumana, was studied. The fastest biomass accumulation was obtained under shaking, with or without illumination, with the highest biomass obtained after 3-4 weeks of growth. The biological activity of chloroform extracts of the culture filtrate was characterised: it contained at least two main toxic metabolites that caused necrosis and wilting of various plants and led to mortality of germinating seeds of O. cernua, O. aegyptiaca, O. ramosa and O. cumana. The highest toxic activity of the chloroform extract was obtained under illumination without shaking after 3-4 weeks of growth. The two toxic metabolites were purified and identified as fusaric acid (FA) and 9,10-dehydrofusaric acid (DFA). Both FA and DFA production began in the first week of growth, increasing gradually to their maxima after 4 weeks. The highest level of pathogenic activity of the fungus was obtained after three or more weeks of fungal growth. It can be concluded that in order to produce high levels of toxin and pathogenic activity, the fungus should be grown under illumination without shaking for 4 weeks

Fusarium verticillioides as a new pathogen of the parasitic weed Orobanche spp.

“…orthoceras, a highly specific fungal pathogen of O. cumana, has already demonstrated high potential as a biocontrol agent for this broomrape species (Dor et al 2007), yet there is still a need for a variety of biocontrol agents toward other parasitic weeds, each occupying different environmental and climatic conditions, and thus the identification of F. verticillioides as an effective pathogen of various broomrape species is potentially applicable, possibly also in synergism with other pathogens, as suggested by Sauerborn et al (2007).…”

“…orthoceras, a pathogen of O. cumana that causes complete mortality of Orobanche spp. germinating seeds and wilting of broomrape flowering shoots, has also been found to produce fusaric acid (Dor et al 2007). …”

“…The filter paper was inserted into a PEB (Dor et al 2007;Hershenhorn et al 1996). A window, approximately 12×20 cm, was cut on one side of the bag to allow easy access.…”

“…Fusaric acid, produced by F. verticillioides, is a well-known toxin of various Fusarium species including those pathogenic to parasitic weeds such as Striga hermonthica, Orobanche cumana and O. ramosa (Abouzeid et al 2004;Dor et al 2007;Idris et al 2003;Zonno et al 1996). Fusaric acid produced by F. nygamai has been proposed as a bioherbicide against Striga spp.…”

Effects of different methods to control the parasitic weed Phelipanche ramosa (L.) Pomel in processing tomato crops

“…In recent years, biological control agents such as fungi have received more attention for the reduction of P. ramosa seed germination (Amsellem et al, 2001;Dor et al, 2007;Joel et al, 2007;Sauerborn et al, 2007). Among the several fungal species used, Fusarium oxysporum Schltdl isolated from diseased P. ramosa has been shown to be highly virulent against this parasite.…”