Disease Note Diseases Caused by Fungi and Fungus-Like Organisms First Report of Fusarium Sheath Rot of Rice Caused by Fusarium incarnatum-equiseti Species Complex in the United States Muhammad Imran, 1,2 Sabin Khanal, 2 Xin-Gen Zhou, 2,† Sanjay Antony-Babu, 3 and Muhammad Atiq 1 1 Department of Plant Pathology, University of Agriculture, Faisalabad 38000, Pakistan 2 Texas A&M AgriLife Research Center, Beaumont, TX 77713, U.S.A. 3 Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843, U.S.A. M. Imran and S. Khanal contributed equally to this work. Funding: This work was financially supported by the Higher Education Commission of Pakistan and Texas Rice Research Foundation (TRRF 2021- 2022). Plant Dis. XXX:XX, XXXX; published online as https://doi.org/ 10.1094/PDIS-12-21-2693-PDN. Accepted for publication 25 April 2022. Fungal diseases, including sheath rot (Sarocladium oryzae), cause sig- nificant losses of yield and milling quality of rice (Oryza sativa). In August 2021, symptoms like sheath rot were observed on 20% of rice plants (cv. Presidio) in a 1-ha field in Eagle Lake, Texas. Initial lesions occurred on the upper flag leaf sheaths and were oblong or irregular oval, with gray to light brown centers, and a dark reddish-brown diffuse margin. Lesions enlarged, coalesced, and covered a large area of the sheath. Infection led to panicle rot with kernels turning dark brown. Unlike sheath rot, sheath infection also led to inside culm infection with irregular dark brown lesions. Infected tissue pieces were sterilized with 1% NaOCl for 2 min, followed by 75% ethanol for 30 s, washed in sterile H 2 O three times, air dried, and incubated on PDA at 27°C. Fungal isolates were obtained from 15 diseased plant samples, and their singled-spored fungal colonies were whitish, loosely floccose, and produced light yellow pigmentation. On carnation leaf agar, macroconidia were slightly curved and tapered at the ends, with three to five septa, and measured 17.5 to 34.3 × 3.1 to 5.0 μm. Microconidia were ovoid, usually with zero to one septa, and 4.0 to 15.5 × 2.5 to 4.5 μm. Spherical chla- mydospores were produced in chains. These morphological characteristics were consistent with those described for the Fusarium incarnatum-equiseti species complex (O’Donnell et al. 2009), including F. incarnatum (Wang et al. 2021) and F. equiseti (Avila et al. 2019). For molecular identification, DNA of a representative isolate was extracted and the ITS, LSU, and EF1 of the fungus were amplified using the primers ITS1/ITS4 (Wang et al. 2014), D1/D2 domain region of LSU (Fell et al. 2000), and EF1 (Wang et al. 2014), respectively, and sequenced. The ITS sequence (OL344049) was 99.61% identical to the F. incarnatum-equiseti species complex (FD_01692) in the Fusarium-ID database and 99.61% identical to F. equiseti (LC514690, KY523100, MW016539) and F. incarnatum (MH979697) in the NCBI database. The LSU sequence (OK559512) was 98.77% similar to F. equiseti (MN877913, MN368509) and F. incarnatum (MH877332, MH877326); the EF1 sequence (OK570044) was 99.27% similar to F. equiseti (MK278902) in NCBI. A phylogenetic analysis based on the concatenated nucleotide sequences grouped this isolate in the F. incarnatum-equiseti species com- plex clade at 100% bootstrap support. To evaluate pathogenicity, a conidial suspension of 1 × 10 6 conidia/ml or sterilized water (for controls) was injected into the sheaths and young panicles of three rice plants (cv. Pre- sidio) at boot. Treated plants were maintained in a greenhouse at 25 to 30°C. After 3 weeks, typical symptoms, like those observed in the field, developed on the inoculated plants but not on the controls. The same fungus was consistently reisolated from the diseased plants. To our knowledge, this is the first report of Fusarium sheath rot caused by the F. incarnatum-equiseti species complex in rice in the United States. The F. incarnatum-equiseti species complex has been reported to be associated with panicle infection in wild rice (O. latifolia) in Brazil (Tralamazza et al. 2021). F. incarnatum has also been reported to cause panicle rot in China (Wang et al. 2021). F. proliferatum has been reported to cause Fusarium sheath rot in India (Prabhukarthikeyan et al. 2021) and the United States (Cartwright et al. 1995). This research demonstrates the potential of different pathogens being involved in causing sheath rot of rice. References: Avila, C. F., et al. 2019. Int. J. Food Microbiol. 306:108267. Cartwright, R. D., et al. 1995. Phytopathology 85:1199. Fell, J. W., et al. 2000. Int. J. Syst. Evol. Microbiol. 50:1351. O’Donnell, K., et al. 2009. J. Clin. Microbiol. 47:3851. Prabhukarthikeyan, S. R., et al. 2021. Plant Dis. 105:704. Tralamazza, S. M., et al. 2021. Int. J. Food Microbiol. 345:109127. Wang, L., et al. 2021. Plant Dis. 105:3306. Wang, Q.-M., et al. 2014. Persoonia 33:41. The author(s) declare no conflict of interest. e-Xtra Keywords: Fusarium equiseti, Fusarium incarnatum, Fusarium incarnatum- equiseti, Fusarium proliferatum, Fusarium sheath rot, Oryza latifolia, Oryza sativa, rice, Sarocladium oryzae, sheath rot † Indicates the corresponding author. X.-G. Zhou; xzhou@aesrg.tamu.edu © 2022 The American Phytopathological Society Plant Disease / 1