Population, Virulence, and Mycotoxin Profile ofFusariumspp. Associated With Basal Rot ofAlliumspp. in Vietnam

Abstract

Fusarium basal rot (FBR) is particularly problematic to Allium producers worldwide. In Vietnam, information on the profile of FBR is scarce, despite the presence of Fusarium spp. in Allium plants has long been recorded. In the present study, a total of 180 isolates of Fusarium spp. were recovered from Allium bulbs/plants showing symptoms of FBR in 34 commercial Allium fields around Da Lat, Lam Dong (Vietnam). These isolates were identified to the species level by using sequencing the ITS region and the translation elongation factor 1α (TEF-1α) gene. F. oxysporum was found to be most prevalent (81%) in samples from all locations and Allium varieties, followed by F. solani (15%) and F. proliferatum (4%) which was only found in onion (Allium cepa L.). Pathogenicity tests on onion seedlings (56 isolates) and mini bulbs (10 isolates) indicated that onion can be infected by all these species, but that the virulence varied greatly between isolates. Moreover, isolates that were virulent on seedlings were sometimes not virulent on bulbs and vice versa, which points to a specialization of isolates for the host phenology. Mycotoxin analyses showed that the highest amounts of beauvericin were detected in seedlings and bulbs infected by F. oxysporum, whereas F. proliferatum was mainly responsible for the presence of fumonisin B1 in bulbs, suggesting a natural occurrence of beauvericin and fumonisin B1 in onions infected by these pathogens.

Phenology‐regulated defence mechanisms as drivers for Fusarium basal rot in onion (Allium cepa)

“…For F. proliferatum , research on its interaction with Allium is still in its infancy and no information is available on virulence factors involved in host colonization. A set of interesting cyclodepsipeptide secondary metabolites, including beauvericin (BEA) and fumonisin B 1 (FB 1 ), were recently detected in onion after artificial infection with Fusarium species (Le et al, 2020). BEA is an intracellular phytotoxin and an inhibitor of young leaf respiration (Pavlovkin et al, 2012).…”

“…The incidence of the disease decreases with seedling age (Le et al, 2021) but becomes more severe again once the bulbs are either fully developed or at the postharvest stage (Cramer, 2000). We have previously found that the aggressiveness across Fusarium isolates associated with FBR varies according to the host developmental stage (Le et al, 2020).…”

Assessment of Commercial Fungicides against Onion (Allium cepa) Basal Rot Disease Caused by Fusarium oxysporum f. sp. cepae and Fusarium acutatum

“…Furthermore, there is a fear that infected onions without visual symptoms will reach markets across the country. This concern is strengthening since known toxins are produced by this pathogen genius [6].…”

Streptomyces Strains Promote Plant Growth and Induce Resistance Against Fusarium verticillioides via Transient Regulation of Auxin Signaling and Archetypal Defense Pathways in Maize Plants

“…In this study, an F. verticillioides strain F01.12 (accession number MZ559332 ) isolated by Tran et al (2021a) was used. In addition, five other Fusarium strains comprising F. proliferatum and F. mangiferae were isolated from maize grains in the central highlands of Vietnam ( Tran et al, 2021b ), F. oxysporum , and F. solani isolated from onion in Dalat, Vietnam ( Le et al, 2020 ) and F. graminearum PH1 isolated from wheat ( Gale et al, 2005 ) were also used. Each fungus was cultured on a PDA plate (Potato Dextrose Agar, 40 g L –1 ) (Sigma Aldrich, Overijse, Belgium) for 7 days at 25°C before performing assays.…”