Identification and fungicide sensitivity of Microdochiumchrysopogonis (Ascomycota, Amphisphaeriaceae), a new species causing tar spot of Chrysopogonzizanioides in southern China.

Vetiver grass (Chrysopogonzizanioides) has received extensive attention in recent years due to its diverse applications in soil and water conservation, heavy metal remediation, as well as essential oil and phenolic acids extraction. In 2019, the emergence of tar spot disease on C.zizanioides was documented in Zhanjiang, Guangdong Province, China. Initially, the disease manifested as black ascomata embedded within leaf tissue, either scattered or clustered on leaf surfaces. Subsequently, these ascomata became surrounded by fisheye lesions, characterised by brown, elliptical, necrotic haloes, which eventually coalesced, resulting in leaf withering. Koch's postulates demonstrated that the fungus isolated from these lesions was the causal agent. Microscopic examination showed that the pathogen morphologically belonged to Microdochium. The phylogenetic tree inferred from the combined ITS, LSU, tub2 and rpb2 sequences revealed the three isolates including GDMCC 3.683, LNU-196 and LNU-197 to be a novel species of Microdochium. Combining the results of phylogenetic, pathogenicity and morphological analyses, we propose a new species named M.chrysopogonis as the causal agent of C.zizanioides in southern China. The optimum growth temperature for M.chrysopogonis was determined to be 30 °C. The in vitro fungicide sensitivity of M.chrysopogonis was determined using a mycelial growth assay. Four demethylation-inhibiting (DMI) fungicides, including difenoconazole, flusilazole, propiconazole and tebuconazole and one methyl benzimidazole carbamate (MBC) fungicide, carbendazim, were effective against M.chrysopogonis, with mean 50% effective concentration (EC50) values of 0.077, 0.011, 0.004, 0.024 and 0.007 µg/ml, respectively. These findings provide essential references for the precise diagnosis and effective management of M.chrysopogonis.

Comprehensive utilization of edible mushroom Auricularia auricula waste residue-Extraction, physicochemical properties of melanin and its antioxidant activity.

In order to promote the comprehensive utilization of the Auricularia auricula waste residue, the extraction process and the physicochemical properties of melanin from A. auricula waste residue were studied. Furthermore, the chemical antioxidant activity of waste residue melanin and its protective effect on cell oxidative injury induced by H2O2 were investigated. The results indicated that the ultrasonic-assisted extraction process could be used to extract the melanin from A. auricula waste residue. Melanin had a good solubility in alkali solution and exhibited a certain stability to thermal. There was no significant difference between A. auricula melanin control group and waste residue melanin on ABTS, DPPH, and hydroxyl radical scavenging activity. Waste residue melanin significantly inhibited the cell death caused by H2O2, and the cell viability was restored to 98.09 ± 5.97% when the melanin concentration was 1.6 mg/ml. Cell morphology observation confirmed that the melanin ameliorated the morphological changes of cells induced by oxidative stress.