Aetiology of garlic rot, an emerging disease in France

Abstract

The incidence of garlic rot has constantly increased in France since the early 2000s.To set up an efficient method of garlic protection against this disease, we have clarified its aetiology. This was achieved by surveying garlic from the two main French basins of garlic production over 3 years. Fungi were isolated from 5,493 garlic cloves belonging to pink, purple, and white garlic types. Sequencing of the translation elongation factor 1α gene of 1,171 strains revealed that 94% of the strains belonged to the species Fusarium proliferatum and 6% belonged to F. oxysporum. The pathogenicity of both species on garlic was confirmed by artificial inoculations and reisolations. There was significantly more F. oxysporum in garlic cloves with symptoms coming from the southeast basin (9.44%) than from the southwest basin (2.76%). This study confirms that garlic rot is present in pink, purple, and white types. However, pink type garlic harbours F. oxysporum significantly less frequently (1.59%) than white (9.39%) and purple (7.34%) types. Sequencing of rpb1, rpb2, ITS, and IGS regions of a subsample of strains revealed that there is little genetic diversity in the French population of F. proliferatum.

Fusarium Dry Rot of Garlic Bulbs Caused by Fusarium proliferatum: A Review

“…In all cases, F. proliferatum has been the predominant Fusarium species associated with dry rot. FDR is the most frequently detected postharvest disease in Spain, found in up to 50% of the samples analyzed [9], coinciding with the results of Chrétien et al [2] in France, who observed 55% of the peeled cloves with typical Fusarium symptoms. In Italy, FDR was observed in 71.4% at harvest and 82.1% during postharvest storage [16].…”

“…Fusarium culmorum [23] and F. verticillioides [35] have rarely been isolated [16]. In Spain, Gálvez and Palmero [9] reported isolation percentages of F. proliferatum over 80%, agreeing with Chrétien et al [2] in France. In all cases, F. proliferatum has been the predominant Fusarium species associated with dry rot.…”

“…F. proliferatum is the most frequently isolated species from symptomatic cloves. Moreover, F. oxysporum [2,16,32,35] and F. solani [9,31] have also been reported. Fusarium culmorum [23] and F. verticillioides [35] have rarely been isolated [16].…”

“…Thus, DNA sequencing is the best option for the identification to species level using the TEF1 gene and currently, it is complemented with multilocus sequence typing (MLST) through the addition of two partial sequences from the two largest DNA-directed RNA polymerase subunits (RPB1 and RPB2) [59,60]. In fact, in most studies on garlic, F. proliferatum has been identified by sequencing of the TEF1 gene [2,9,10,[28][29][30]. Torres-Cruz et al [61] discussed using portions of three phylogenetically informative genes (i.e., TEF1, RPB1, and RPB2) for resolving at or near the species level in every Fusarium species.…”

“…The worldwide production of garlic has been steadily increasing over the last 20 years. In 2020, more than 28 million tons were produced on more than 1.6 million ha, mostly located in tropical and temperate regions [2,3]. Garlic is a strategic crop for many regions from not only the economic point of view, but also the social [4].…”