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Ear rot is one of the most prevalent and destructive diseases on maize. During field surveys in recent years, it was found that a Penicillium ear rot broke out in some areas of Shanxi, Shaanxi, Hebei and Tianjin in China, with an incidence of 3%-90%. A Penicillium sp. was isolated from diseased kernels covered with greyish green mold, and three isolates were identified by morphological and molecular characteristics. The pathogenicity of isolate ZBS205 to maize ears was further determined by artificial inoculation in a field. Furthermore, the sensitivity of isolate ZBS205 against six commonly-used fungicides was also evaluated. According to macro- and micro-morphological characteristics, isolate ZBS205 was generally identical to Talaromyces funiculosus (teleomorph of P. funiculosum). The partial gene sequences of the nuclear ribosomal ITS1-5.8S-ITS2 (ITS) region, β-Tubulin, putative ribosome biogenesis protein (Tsr1) and the second largest subunit of the RNA polymerase II (RPB2) from isolates ZBS205, D49-1 and S73-1 showed the highest nucleotide identity to T. funiculosus strain X33, and the phylogenetic analysis conducted by neighbor-joining method with the combined data of the four genes demonstrated that these three isolates clustered with T. funiculosus strain X33. These results suggested that the fungus isolated from diseased maize kernels was T. funiculosus. Pathogenicity testing showed that the T. funiculosus isolate ZBS205 was pathogenic to maize ears, which showed symptoms of rotted cob and deteriorated kernels. This is the first report of T. funiculosus as the definitive pathogen causing maize ear rot. The result of fungal sensitivity against fungicides showed that pyraclostrobin exhibited the highest toxicity to mycelial growth and could be used as a candidate agent for the prevention and control of T. funiculosus ear rot. Results of the present study provide a basis for understanding ear rot caused by T. funiculosus, and should play an important role in disease management.

Maize (Zea mays L.) is one of the most important cereal crops in China, and the planting area reached 41.3 million hectares in 2019. Root rot is a widespread disease that occurs at the seedling stage of maize, resulting in leaf wilting, root rot and even plant death, and consequently yield and quality losses. During an investigation of spring maize in 2020, seedlings with wilted leaves and dark brown necrotic spots on root were observed in the fields in Kuancheng Manchu Autonomous County, Hebei Province, China. Symptomatic plants were collected for pathogen isolation and identification. The soil on roots was washed off with running water. Then, 2-3 mm necrotic root segments were sampled and surface sterilized with 75% ethanol for 2 min, rinsed three times with sterile distilled water, air-dried on sterile filter paper, and plated on potato dextrose agar (PDA). Plates were incubated at 28℃ in darkness for 3 days. A nonsporulating, dematiaceous fungus growing from root segments was transferred to fresh PDA plates. The colonies were round or irregular round, black, villiform with dense grayish white mycelia. Water agar amended with wheat straw was used for sporulation. Conidiophores were single, light brown, multiseptate, geniculate. Conidia were 38.68 x 10.69 to 71.98 x 20.57 μm, brown, oval, slightly curved, with 2 to 8 septa, and an obviously flattened hilum on the basal cell. Conidia germinated from both poles. The causal agent was identified as Bipolaris zeicola (G.L. Stout) Shoemaker (teleomorph = Cochliobolus carbonum R. R. Nelson) based on its morphological features. For molecular identification, genomic DNA was extracted from fresh mycelia cultured on PDA plates. Partial sequences of ITS-rDNA region and Brn1 reductase melanin biosynthesis gene were amplified using primers ITS1/ ITS4 (TCCGTAGGTGAACCTGCGG/ TCCTCCGCTTATTGATATGC) (White et al. 1990) and Brn01/ Brn02 (GCCAACATCGAGCAAACATGG/ GCAAGCAGCACCGTCAATACCAAT) (Shimizu et al. 1998), respectively. A DNA fragment of 532 bp was obtained from ITS-rDNA region and the sequence (GenBank Accession No. MW407046) was 100% identical to sequence of B. zeicola (GenBank Accession MH864760). The sequence of Brn1 gene was 816 bp (GenBank Accession No. MW415899) and was 99.75% identical to sequence of C. carbonum (GenBank Accession No. AB011658). The morphological and molecular evidence proved that the causal agent isolated from maize roots in Hebei province was B. zeicola. Pathogenicity assays were conducted with one week old (V1 stage) maize seedlings grown from the surface-sterilized seed of cv. Zhengdan 958. The mesocotyl and radicle of each plant (N=3) were inoculated with a 5 mm fungal disk of B. zeicola. Mock-inoculated plants (N=3) with sterile PDA disk served as the negative control. After 7 days, plants inoculated with B. zeicola were wilted with dark brown necrotic spots on mesocotyl and radicle. Meanwhile, the negative controls did not present any symptoms. Koch’s postulate was proved with successful re-isolation of the same fungus from the inoculated maize plants. These results confirmed the pathogenicity of B. zeicola on maize root. B. zeicola mainly causes an important foliar disease in many regions of the world, known as Northern corn leaf spot, in addition, it can also cause ear rot and stalk rot of maize (Liu et al. 2015). To our knowledge, this is the first report of root rot caused by B. zeicola on maize in China, which extends the known agents of maize root rot. Therefore, it is necessary to explore effective seed-applied fungicides for disease control. Also, more attention should be paid to develop hybrids with resistance to this disease.