First Report of <i>Talaromyces pinophilus</i> Causing Soybean Leaf Blight in China

In June 2025, leaf blight symptoms were observed in five soybean fields (Glycine max L. variety ‘ZH13’), each approximately 300 m2 in size, located in Nantong Municipality, China (32.23° N, 120.73° E), in the northern part of the Yangtze delta. Symptoms, which had not been previously reported in the region, were unusual and consisted of irregular necrotic brown spots surrounded by dried-up yellow halos (Fig. 1). Between 50% and 60% of leaves exhibited symptoms. Five isolates, NJC100, NJC101, NJC102, NJC103, and NJC104, were each obtained from a different symptomatic leaf tissue via single spore isolation. These isolates formed white mycelium with green pigmentation on PDA medium after 5 days at 25 °C. Morphological analysis of isolate NJC101 showed the presence of round conidia (4.12 ± 0.56 μm diameter; n = 75) and branched conidiophores, consistent with the morphology expected for Talaromyces. The ITS and TUB2 fragments were amplified using the primers ITS1/ITS4 and Bt2a/Bt2b, respectively (Huang et al. 2022). Primers for the amplification of CaM and RPB2 were designed using SnapGene 6.0.2 (CaM: 5’-CAATGTTGTGGTGGATGG-3’ / 5’-GAATTCGTTGTCTAGAAAAAACC-3’; and RPB2: 5’-CGTCCAGCGATGCGTTGAAA-3’ / 5’-CAGTGATTGAACACATCAAAGCC-3’). The sequences were submitted to GenBank (NJC100: PX889850, PX899385, PZ196210, and PZ196215; NJC101: PX889849, PX899386, PZ196211, and PZ196216; NJC102: PX897963, PX899387, PZ196212, and PZ196217; NJC103: PX897964, PX899388, PZ196213, and PZ196218; NJC104: PX897965, PX899389, PZ196214, and PZ196219). A BLAST search indicated that the ITS fragments of these isolates were identical and exhibited 98.64% identity with the ITS sequence of the ex-type strain Talaromyces pinophilus CBS 631.66. The TUB2 fragments of the isolates shared between 98.81% and 98.99% identity with the TUB2 gene of the same strain. CaM sequences showed 98.84%-99.30% identity, while RPB2 sequences showed 99.00%-99.33% identity, with the ex-type strain. This suggested that these isolates belong to the T. pinophilus species. A phylogenetic tree was constructed using ex-type and representative Talaromyces strains (Visagie et al. 2024) and is shown in Fig. 2. To confirm pathogenicity, the isolates were spray-inoculated on one-month-old ‘ZH13’ soybean plants. Plants were maintained at 28 °C and 60% relative humidity, and symptoms were photographed after 3 days. The pathogen was re-isolated from the lesions, and its identity was confirmed via ITS sequencing and morphological analysis, fulfilling Koch’s postulates. Interestingly, only isolates NJC100, NJC101, NJC102, and NJC103 caused lesions but not NJC104, suggesting that the latter lacks pathogenicity. A few avirulent T. pinophilus strains have previously been used as biocontrol agents for the management of pathogenic fungi (Bennacer et al. 2025), suggesting the potential use of the isolate NJC104 as a biocontrol strain. Various Talaromyces species have been reported to cause postharvest fruit rot in oranges, tomatoes, quinces, pears, and pomegranates (Mukhtar et al. 2019; Stosic et al. 2020, 2021). T. pinophilus was previously identified as the causal agent of rot in postharvest Lanzhou onions (Wang et al. 2024). Here, we report for the first time T. pinophilus as a pathogen on soybean leaves and the first record of the ability of a Talaromyces species to cause foliar disease. This represents an important milestone in understanding the host range of this fungal species.