First report of Fusarium commune Causing Bulb Rot on Lily (Lilium brownii var. Viridulum Baker) in Hunan Province of China.

Lily (Lilium brownii var. Viridulum Baker) is a well-known edible plant with large, white and sweet bulb scales that has important medicinal value (Zhou et al. 2021) and is grown mainly in the Hebei, Shanxi and Henan provinces of China. In May 2021, a case of bulb rot was discovered in a 3.33 hm2 plantation in Huaihua, Hunan Province, affecting 20% of the area (27°59'30″N, 110°32'20″E). The disease is most severe during the rainy season in May and June. In the early stage, irregular brown spots appeared on the lily scales, the necrosis was depressed and gradually enlarges, and in the later stage, the scales were scattered from the base of the disc and slough off. Ten samples were taken randomly from different plants in the plantation area to isolate the pathogens. After washing with sterile water, they were cut into small pieces and sterilised with 3% hydrogen peroxide for 30 s, 75% ethanol for 90 s, rinsed three times with sterile water and dried on sterile filter paper, then placed on a water agar plate and incubated in the dark in a constant temperature incubator at 28℃ for 3 to 5 days. After 2 days, the mycelium at the edge of the colony was transferred to a PDA plate and incubated for 3-5 days at 28°C in the dark to obtain pure fungal isolates. Eighteen purified fungal isolates were obtained, of which sixteen looked like Fusarium (88.9% isolation rate) and three representative isolates (BHBR2, BHBR3 and BHBR5) were selected for further study. The surface of this fungus was white with dense aerial mycelium. Some had an orange centre in the medium. Microconidia were oval in shape and appeared either straight or slightly curved. These microconidia were colourless, had 0-1 septa and measured 3.334 to 14.724 × 2.216 to 5.385 µm (n=100). Macroconidia were predominantly three-septate, crescent-shaped structures that were thin-walled and slightly curved. Cells at the apex and base were similarly curved. Macroconidia measured 17.956 to 32.150 × 2.788 to 4.492 µm (n=100). The mitochondrial small subunit (mtSSU) and translation elongation factor 1-α (TEF1) genes were amplified and sequenced using the NMS1/NMS2 and TEF-R/TEF-F primers to verify the identity of the pathogens (Stewart et al. 2006). The sequences were submitted to GenBank (BHBR2: mtSSU, PP273435; TEF, OR900976; BHBR3: mtSSU, PP277729; TEF, OR900977; BHBR5: mtSSU, PP277728; TEF, OR900978). A concatenated phylogenetic tree of the two genes was constructed and analysis showed that BHBR2, BHBR3 and BHBR5 were significantly clustered with Fusarium commune. Based on the results of morphological identification and phylogenetic tree analysis, the three isolates were identified as Fusarium commune. We carried out pathogenicity tests using two methods, one in which 6 × 6 mm fungal blocks were inoculated on lily (L. brownie var. viridulum Baker) scales and controls inoculated with sterile blocks, and the other in which strain BHBR2 was selected to carry out pathogenicity tests on bulbs of live plants soaked with 50 ml of a 1 × 106 conidial suspension and bulbs of control plants soaked with sterile water, all in three replicates. They were placed in a growth chamber at 28°C and 80% relative humidity, and the scales were moistened with moistened sterile filter paper. After 3 days of rearing treated scales, lesions appeared on lily scales inoculated with mycelial blocks and expanded with time, whereas no lesions appeared on lily scales inoculated with sterile blocks. One month later, whole plants soaked in the spore suspension wilted, while the control plants grew well. The pathogens re-isolated from the diseased tissues had the same morphological characteristics as representative isolates. This confirms Koch's hypothesis. Fusarium commune has been shown to be the most important pathogenic fungus causing root rot in Alfalfa (Medicago sativa) (Yang et al. 2022) and blueberry (Vaccinium uliginosum L.) (Li et al. 2023) in China. To our knowledge, this is the first report of Fusarium commune causing lily bulb rot in the world, which will lay the foundation for future control of lily bulb rot.

First report of Fusarium tricinctum Causing Leaf Blight on Amorphophallus konjac in Hunan Province of China.

Konjac (Amorphophallus konjac) is a perennial herbaceous plant of the Araceae family, cultivated mainly in south-western China and used extensively for weight loss (Chua et al. 2010). In June 2022, leaf blight was detected on a 2,00 ha A. konjac plantation in Chenxi County, Huaihua City, Hunan Province. It infected almost 20% of the area under cultivation and tends to occur each year during warm, humid weather from May to July, causing significant economic losses to A. konjac production. There were small brown spots on the leaves which gradually spread to form irregular brown lesions. In severe cases the entire plant turned yellow and died. Nine samples were collected randomly from different plants in three plantation forests to isolate the pathogens. They were washed with sterile water and the lesions were excised. They were subsequently disinfected with 3% hydrogen peroxide for 30 s, 75% ethanol for 90 s and rinsed three times with sterile water. The cut sections were then placed on water agar plates and grown in the dark in a constant temperature incubator at 28℃ for 3-5 days, when mycelia grew they were transferred to potato dextrose agar medium and grown in the dark at 28℃ for 3-5 days. Eleven purified fungal isolates were obtained, ten of which looked like Fusarium (90.9% isolation rate), and three representative isolates (MY5, MY7 and MY9) were chosen for further study. The fungal colonies initially appeared white and gradually turnned dark red. Macroconidia were crescent-shaped, elongated, slightly curved and had 2 to 4 septations, with a predominance of 3 septations. They measured 15.540 to 42.083 × 2.760 to 4.558 µm (n=100). Microconidia were oval or pyriform, with a maximum of one septum and measured 6.135 to 24.990 × 2.158 to 4.412 µm (n=100). Two genetic regions, the translation elongation factor-1 (TEF1-α) and RNA polymerase II largest subunit (RPB1) genes, were amplified and sequenced to verify the identity of the fungus (Qiu et al. 2023). The universal primers TEF1-F/R, G2R/Fa were used for amplification and sequencing, and the sequences were submitted to GenBank (TEF1-α: OR545395, OR545397, OR545399; RPB1: OR545394, OR545396, OR545398). A joint phylogenetic tree of the two genes was constructed and analysis showed that the three isolates were significantly clustered with Fusarium tricinctum. Based on the results of morphological identification and phylogenetic tree analysis, the three isolates were identified as F. tricinctum. Pathogenicity tests were carried out on 12 uniformly growing leaf expansion stages of konjac plants，each inoculated with five young leaves. Mycelial blocks of 6 × 6 mm grown on PDA media for 5 days were placed on the surface of the leaves, while sterile PDA blocks were placed on the control plant. After 10 days of rearing the treated plants in a constant temperature chamber at 28°C and 90% relative humidity, the lesions appeared and the pathogens re-isolated from the diseased tissues had the same morphological characteristics as representative isolates. F. tricinctum has been shown to be the major pathogenic fungus causing leaf blight in wheat (Triticum aestivum L.) (Castañares et al. 2011) and orchardgrass (Dactylis glomerata L.) (Wu et al. 2020). To our knowledge, this is the first time in the world that F. tricinctum has been reported to cause leaf blight in A. konjac. This research could provide a foundation for future control of leaf blight disease.