First report of the gall midge Asphondylia serpylli on thyme (Thymus vulgaris), and identification of the associated fungal symbiont

Abstract

Asphondylia spp. (Diptera: Cecidomyiidae) are known for inducing gall formation on many diverse plants in both wild and agricultural contexts. The species Asphondylia serpylli is herewith reported for the first time on thyme (Thymus vulgaris) cropped in Poland. The associated fungus has been identified as Botryosphaeria dothidea, representing its first record from cecidomyiid galls on a species of Lamiaceae. Moreover, a short account is given on the parasitoid species active in this particular ecological context. These findings point out the basic role of B. dothidea in the organization of these three-component biotic systems regardless of the varied assortments between the midge species and their host plant.Asphondylia serpylli on thyme B. Zimowska et al.

Phylogenetic Characterization of Botryosphaeria Strains Associated with Asphondylia Galls on Species of Lamiaceae

“…They were smooth, hyaline, mostly with granular content, fusiform or irregularly fusiform, wider in the middle to upper third, base-truncate or subtruncate with rounded apex, and quite variable in size (Table 4). Muriform conidia referable to the synanamorphic stage Dichomera were never observed, unlike what previously resulted in subcultures of strains from galls collected on T. vulgaris directly prepared from the isolation plates [3]. This failure was assumed to possibly derive from prolonged storage at 4 • C of the stock cultures of our strains.…”

“…and Alternaria spp., have been frequently reported as gall associates, basically in connection with their saprophytic aptitude, which occasionally makes them conceal the real symbiont during the isolation procedure [1][2][3][4]. On the other hand, nomenclatural inconsistency, which only recently has been resolved after the epitypification of B. dothidea [5], may account for some previous incorrect reports referring to Macrophoma, Diplodia, and Dothiorella [2,3,6,7]. Indeed, taxonomists recommend a careful interpretation of past literature concerning this fungus [8,9].…”

“…However, their distribution appears to reach Central Europe, following the geographical spread of some hosts, as documented in the case of A. serpylli and A. hornigi, respectively associated with Thymus spp. and Origanum vulgare [3,13]. In the course of our investigations on a number of species of Lamiaceae, we had the opportunity to collect isolates from galls of Asphondylia spp.…”

New Cladosporium Species from Normal and Galled Flowers of Lamiaceae

“…Asphondylia galls were only found on Clinopodium nepeta, C. vulgare, Micromeria fruticulosa, M. graeca in Italy, and T. vulgaris in Poland, which implies that the isolates from the other species were all obtained from normal flowers. Isolation of fungal associates from gall walls and inquilines, that is midge larvae or their parasitoids, was carried out as specified in previous papers [ 23 , 24 ]. Isolations from the inner flower parts (receptacle, ovaries, or achenes developing inside the flower calyx) were carried out on potato-dextrose agar (PDA: Difco, Paris, France) amended with streptomycin sulphate (200 mg L −1 ), after dissecting the flowers with a sterilized scalpel in a laminar flow hood.…”

“…In the course of a cooperative investigational activity on the fungal associates developing in galls produced by midges of the genus Asphondylia in flowers of several species of Lamiaceae [ 23 , 24 ], strains of Cladosporium were frequently recovered during the isolation attempts. However, unlike Botryosphaeria dothidea which was only isolated from galls [ 25 ], Cladosporium isolates were also obtained from the inner parts of normal flowers and from achenes, indicating that their presence in the flower microenvironment is independent by the insect, and is likely to not affect flower physiology.…”