First Report of Fusarium lacertarum Causing Fusarium Wilt on Sesame ( Sesamum indicum ) in Hebei Province, China
Sesame (Sesamum indicum L.) is an important oilseed crop widely cultivated in China. In August of 2025, wilt symptoms were observed on sesame (cv. Jizhi No. 1, 2, etc.) in a field in Shijiazhuang, Hebei, China. Affected leaves turned yellow and necrotic from the lower to upper portions but remained attached. Longitudinal yellowish-brown lesions occurred at the stem base, with pink sticky sporodochia under high humidity. Infected plants eventually died. Disease index was calculated according to Xu et al. (2026) with minor modifications, ranging from 11.2% (cv. Jiheizhi No. 8) to 55.2% (cv. Jizhi No. 1) across nine plots (250 plants/plot, with three replicates). Symptomatic stems were collected for fungal isolation. Small pieces (5 ⅹ 5 mm) were surface-sterilized (70% ethanol 30 s, 1% NaClO 2 min), rinsed, and plated on PDA at 25°C with 12-h photoperiod for 3-7 days. The single-spore method was used to purify the obtained isolates. Based on morphological and cultural characteristics, combined with ITS sequencing, a total of 48 isolates were preliminarily divided into two groups, with isolation frequencies of 68.8% and 31.2%, respectively. Representative isolates, ZM1 and ZM2, were selected for further study. On PDA, ZM1 colonies reached 70.9±3.3 mm diameter after 7 days, with white to pale-violet aerial mycelia, irregular margins, and purple reverse pigment. Macroconidia were hyaline, slender, straight to slightly curved, foot-shaped basal cell, tapering apical cell, 3–5 septate, 34.3±10.6 × 4.0±0.3 μm (n=200). Microconidia were abundant, hyaline, oval to kidney-shaped, 0–1 septate, 11.9±3.3 × 3.2±0.2 μm (n=200). Chlamydospores absent. ZM2 colonies reached 85.8±1.6 mm diameter after 7 days, with white aerial mycelia, orange reverse pigment, irregular margins. Macroconidia were hyaline, slender, curved, falcate, with foot-shaped basal cell, tapering to hooked apical cell, 1-4 septate, 26.0±8.8 × 4.5±0.7 μm (n=200). Microconidia absent. Chlamydospores were globose to subglobose, in chains, intercalary or terminal, with an average diameter of 10.9±1.6 μm. These traits matched Fusarium species (Leslie and Summerell, 2006). Molecular characterization was performed based on ITS, TEF-1α, and RPB2 (Xu et al., 2026). BLAST analysis revealed that ZM1 showed 100% (ITS and RPB2) and 99.5% (TEF-1α) similarity with F. oxysporum references, and ZM2 showed 100% similarity with F. lacertarum references across all three loci. Multi-locus phylogenetic analysis (ML), based on TEF-1α-RPB2 sequences, confirmed that ZM1 clustered with F. oxysporum (CBS 144134, 97% bootstrap) and ZM2 with F. lacertarum (NRRL20423, 99% bootstrap). All sequences were deposited in GenBank (ZM1: PZ288046/PZ291680/PZ453744; ZM2: PZ288047/PZ291681/PZ453745). Pathogenicity tests were conducted on 1-month-old sesame seedlings (cv. Jizhi No.1). Conidial suspension (1 × 10⁶ conidia/mL, 25 mL/pot) was poured around the stem base and root zone without wounding (ten plants per treatment, twice replicates); controls received sterile water. All plants were covered with plastic film for 24 h, then uncovered and maintained at 25°C, 12-h photoperiod. After 14 days, all inoculated plants exhibited typical wilt symptoms; controls remained symptomless. F. oxysporum and F. lacertarum were reisolated from ZM1- and ZM2-inoculated plants, respectively, fulfilling Koch’s postulates. F. oxysporum is a well-known causal agent of Fusarium wilt on sesame worldwide (Duan et al., 2020). Although less frequent, F. lacertarum was confirmed pathogenic and represents the first report of this species causing sesame wilt in China. F. lacertarum has previously been reported on Sorghum bicolor in North Carolina (Beacorn and Thiessen, 2021) and Casuarina equisetifolia in Brazil (Poletto et al., 2015). The identification expands the host range of F. lacertarum and highlights the importance of monitoring emerging Fusarium species in sesame production.