First report of Kabatiella zeae causing eyespot of maize (Zea mays L.) in Uruguay

Maize (Zea mays L.) is a major crop worldwide used as livestock feed, for human food and in industry. In March 2025, in a field located at 33°31'31.0"S, 58°09'03.1"W, Dolores (Uruguay), small circular to oval lesions (1-3 mm diameter) were observed on maize cultivar DK72-70TRE, particularly on upper leaves, at R4 phenological stage. The lesions were cream to brown in colour and surrounded by a narrow halo, which sometimes coalesced to form larger necrotic areas. Disease incidence was 100% and severity on leaves calculated visually was approximately 40% on 500 plants surveyed. Six representative affected plants were randomly collected. Leaf fragments, 5-cm length, containing lesions were cut, surface sterilized using 1% sodium hypochlorite for 30 s, followed by 70% ethanol for 30 s, and then rinsed twice with sterile distilled water. Then, the samples were placed in humid chambers at room temperature. After 48 h of incubation, mycelial growth on the lesions was picked with a hypodermic needle, placed on acid potato dextrose agar (APDA) and incubated at 25°C. Growing colonies were transferred to fresh potato dextrose agar (PDA). Colonies were slow-growing and initially colourless assuming a pink leathery appearance after 7 days, and becoming black after 15 days. Hyaline hypha were broad, branched, septate with slight constrictions at the septa. Spores were produced successively on the tips of short conidiophores or along the hyphae near septa. Conidia were hyaline, long, curved to falcate with pointed ends, and non-septate measuring 20 to 35 × 2.5 to 3.75 μm (average: 28.16 × 3.54 μm, n = 100). These morphological features were similar to those of Kabatiella zeae Narita & Y. Hirats. (syn. Aureobasidium zeae) (Narita and Hiratsuka, 1959). Internal transcribed spacer (ITS) and large subunit ribosomal RNA (LSU) regions of isolate KO were sequenced to confirm its identity. Both sequences were deposited in GenBank under accession numbers PV875371 for ITS and PV875375 for LSU, which exhibited 99.45% and 100% sequence identity, respectively, to K. zeae strain JIMHK-9 (Chen et al., 2021). Maize plants cv. DK72-70TRE at V6 phenological stage, grown in 15 cm-diameter pots were inoculated with isolate KO. Inoculum suspension (106 conidia/ml) was prepared by washing PDA cultures incubated at 25°C for 7 days. Inoculum was applied on the leaves with a hand sprayer until runoff. Plants were kept in a growth chamber at 25°C and 90-95% relative humidity for 24 h, and then they were placed in a greenhouse at around 25°C. Eight plants were inoculated, and water was sprayed over the same number of control plants. Four days post-inoculation, typical small lesions of the disease were observed on the leaves of all plants, while the control plants did not develop symptoms. Morphologically identical isolates to those inoculated were recovered from the leaf lesions on PDA, and their identity was confirmed as K. zeae based on LSU sequencing. This is the first report of K. zeae causing eyespot of maize in Uruguay. The detection of this pathogen could have a negative impact in maize production, as yield losses up to 9% have been reported in United States (Reifschneider and Arny, 1983). Furthermore, it has become one of the major yield limiting factors in maize growing areas of China and it was recognized as a major emerging threat to sorghum (Yu et al., 2024).