First Report of Fusarium equiseti as the Causal Agent of Seed Rot of Matthiola longipetala in Serbia

Abstract

Matthiola longipetala (Vent) DC, commonly known as “night-scented stock” or “evening stock”, is the most widely cultivated species of the genus Matthiola in the family Brassicaceae. It is a common garden flower, available in a variety of colors, many of which are heavily scented and also used in floristry. An elevated incidence of Fusarium was observed during a routine quality control seed assay of M. longipetala obtained from a private production facility in Đurđevo (South Bačka District) in 2018. Fungal infection was noticed on an average of 30% of the tested seed, followed by a reduction in germination. The infected seed was covered with white to beige mycelium. Prior to isolation, seeds were surface sterilized for 10 min with a 1% sodium hypochlorite solution to reduce contaminants, washed twice in sterile water, and plated on potato dextrose agar (PDA). After 7 days of incubation at 25°C under a 12-h/12-h photoperiod of fluorescent light, 14 Fusarium (JBL4089/1 to 14) isolates were single spored and subcultured on both PDA and carnation leaf agar (CLA). Pathogenicity was performed in vitro using a modified PDA slant method in a test tube (Porter et al. 2015). A piece of mycelium of each isolate grown on PDA for 7 days was placed at the bottom of each tube, and dried M. longipetala seed was carefully placed 2 cm above the inoculum. After 10 days, fungal mycelia of 14 isolates completely covered the seedlings, causing seed rot and seedling decay. The Fusarium was reisolated on PDA and used for further analysis in order to morphologically identify the species. Isolate JBL4089/2 formed abundant, loosely floccose, whitish aerial mycelium with beige pigmentation. After transfer to CLA, the isolate formed macroconidia with a tapered and elongated apical cell and prominent foot-shaped basal cell, which were typically four to five septate, with average dimensions of 21 to 60 × 2.8 to 4.6 µm. The isolate formed chlamydospores, but microconidia were not observed. Based on the morphological characteristics, isolate JBL4089/2 was identified as Fusarium equiseti (Corda) Sacc. according to Leslie and Summerell (2006) and Gerlach and Nirenberg (1982). Identification of isolate JBL4089/2 was confirmed by amplification and sequencing of a portion of the translation elongation factor-1 alpha (EF-1α) gene. Total DNA was extracted directly from fungal mycelium with a DNeasy Plant Mini Kit (Qiagen, Hilden, Germany), and PCR amplification was performed with primer pair EF-1/EF-2 (O’Donnell et al. 1998). Sequence analysis of the EF-1α gene revealed 100% nucleotide identity of isolate JBL4089/2 (GenBank accession no. MK061538) with the EF-1α sequences of two F. equiseti isolates from Canada (KU587617 from Pisum sativum and MH315936 from Glycine max) and a Hyssopus officinalis isolate (MK061540) of F. equiseti from Serbia. To our knowledge, this is the first report of F. equiseti as a causal agent of seed rot on M. longipetala in Serbia. The presence of the pathogen could cause significant economic losses in M. longipetala production, and for that reason control strategies for the management of the disease should be implemented.