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|a Strawberry (Fragaria × ananassa Duch.) is an important and very popular fruit around the world because they have unique taste, special fragrance and rich nutrition (Hashmi et al., 2013; Neri et al., 2015). However, mature fruits have the characteristics of smooth texture, high softening rate and re-breathing rate were easily infected by various pathogens (Lara et al., 2004). In June 2022, a few postharvest strawberry fruits were found to rot, soften and cover with a green or yellow mycelium in Kunming city, Yunnan Province (25°02' N; 102°42' E), southwest China. The symptoms of fruits initially observed a tiny white mycelium and water damage, then the mycelium became yellow, with water-soaked areas extended rapidly. Eventually, the entire fruit was covered with yellow, dense mycelium (Fig. 1A, B). The incidence of this postharvest decay in strawberry fruits ranged from 35 to 45% and caused serious loss. This pathogen was isolated from diseased fruit tissues, transferred to potato dextrose agar (PDA) and malt extract agar (MEA), and incubated in the dark at 25 ± 1 ℃. Then purify and separate again. Four pure strains (BDFM1 to BDMF4) were obtained and stored in 15% glycerol at -80 ℃ in the State Key Laboratory for Conservation and Utilization of Bio-Resources Room 1012, Yunnan Agricultural University. On PDA, the colonies were initially white and the reverse was light yellow, after 5 days, the hyphae became golden yellow, and the diameter of the colony reached 5 cm (Fig. 1C). On MEA, the colonies were initially light yellow, and after 4 days, yellow-orange and the reverse were yellow to dark yellow (Fig. 1D). Unbranched sporangiophores are up to 26.7-30.8 μm diameter with columellae frequently pyriform, oblong or ellipsoid, obovoid (43- 60 × 90-135 μm), colorless or yellowish (Fig. 1E), simple or with long or short sympodial branches. Sporangia yellow, globose or subglobose, 55.3-123.7 μm in diameter, wall echinulate, which are spherical formed at the top of the main sporangiophore and each branch (Fig. 1F), Sporangiospores yellow, which are spherical (5.0-8.5 × 5.5-9 μm), oval (21.5-7 × 11-20 μm), thin and smooth-walled. To further identify the fungus, the total genomic DNA was extracted from four strains using the CATB method (Aboul-Maaty & Oraby, 2019). The partial fragments of internal transcribed spacer (ITS), and partial 28S rRNA gene sequence were amplified with the primers ITS1/ITS4, and LR0R/LR5 respectively. These sequences of strains BDFM1 to BDMF4 were uploaded to NCBI GenBank as accessions ON951610, ON951611, ON951612 and ON951613, OP430532, OP430533 OP430534 and OP430535. Using NCBI's BLASTn tools, the nucleotide sequences of strains showed 96.12 - 99.21 % identity to JN206177 (M. inaequisporus strain CBS 496.66). BDFM1 to BDMF4 isolates were used to MEGA11 construct a phylogenetic tree. Maximum likelihood phylogenetic analyses (Fig. 2) and phylogenetic tree from Bayesian method (Fig. 3) further confirmed the results. Pathogenicity tests were conducted with healthy strawberry fruits. We selected two stains (BDFM1, BDFM2) from four same isolates for this test, cultured on MEA for 4 days, then washed with sterilized water and the spore suspensions were adjusted at 1.0 × 106 spores/ml. Ten fruits were surface-disinfected with 75% alcohol for 15 s, rinsed with sterile water 3 times, then air-dried, and sprayed with the spore suspension on the surface, while the control fruits were sprayed with sterile water. The fruits were incubated at 26 °C with 90% relative humidity in a plastic container. This test was performed in triplicate. After 2 days, the fruits sprayed with the spore suspensions showed light yellow hyphae (Fig. 1H), which covered one-third of the fruit surface (Fig. 1G). After 4 days, yellow-orange mycelia covered the entire fruit, with yellow oil-droplets at the tip of the mycelium (Fig. I). Control fruits remained healthy. The fungus was re-isolated and identified as Mucor inaequisporus thus completing Koch's postulates. Mucor inaequisporus was identified by symptoms, morphology (de Freitas et al., 2021), rDNA-ITS sequence analysis, and pathogenicity test. As we know, this is the first report of M. inaequisporus on strawberry fruits in China
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