First Report of Nigrospora oryzae Causing Leaf Spot of Cotton in China

Abstract

Cotton (Gossypium hirsutum L.) is widely cultivated for the important economic value of the fiber. In the summer of 2011, a leaf spot of cotton plants cv. Wanza40 was observed in 11 fields (total of about 4 ha) in Qianshan County in southwest Anhui Province, China. Approximately 30% of the plants in each field were symptomatic. Affected plants exhibited brown to reddish, irregular foliar lesions, each with a brown border near the vein of the leaves. A sign of fungal infection was a dark leaf mold observed on lesions on the abaxial surface of leaves. Sections of symptomatic leaf tissues were surface-sterilized (in 75% ethanol for 30 s, then 1% NaOCl for 1 min), rinsed three times in sterile distilled water, and plated onto potato dextrose agar (PDA). A fungus consistently recovered from symptomatic leaf samples produced colonies that were initially white and then became grayish brown with the onset of sporulation. Black, spherical to subspherical, single-celled conidia (10 to 12 × 14 to 16 μm) were borne on a hyaline vesicle at the tip of each conidiophore. Morphological characteristics of the fungus were similar to that of Nigrospora oryzae (2). The internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) from a representative strain of the fungus, AHC-1, was amplified using the primers ITS1/ITS4 (4) and sequenced (GenBank Accession No. JQ864579). The ITS sequence had 99% identity with >553 bp of the ITS sequence of an N. oryzae isolate (GenBank Accession No. EU918714.1). On the basis of morphological data and ITS rDNA sequence, the isolate was determined to be N. oryzae. A pathogenicity test was performed on detached, young leaves of 4-month-old healthy cotton plants of cv. Wanza40. Six leaves were inoculated by placing a colonized agar piece (5 mm in diameter) from 7-day-old cultures of the fungus on pushpin-wounded leaves. Another six leaves treated with sterile PDA plugs served as a negative control treatment. Leaves were incubated in petri dishes and maintained at 25°C in a growth chamber programmed for 12 hours of fluorescent white light/day. After 5 days, brown to black lesions were observed on all inoculated leaves, whereas no symptoms developed on control leaves. N. oryzae was consistently reisolated from symptomatic leaves but not from the control leaves. N. oryzae is a weak pathogen on a wide range of plants, and has been described as the causal agent of lint rot on cotton (1,3), but to our knowledge this is the first report of N. oryzae causing a leaf spot of cotton in China. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA, Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , April 8, 2012. (2) H. J. Hudson. Trans. Br. Mycol. Soc. 46:355, 1963. (3) A. J. Palmatter et al. Plant Dis. 87:873, 2003. (4) T. J. White et al. In: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

A Victorivirus and Two Novel Mitoviruses Co-Infected the Plant Pathogen Nigrospora oryzae

“…Nigrospora oryzae is a weak parasite plant pathogenic fungus that has a broad host range of over 300 plant species (). This fungus always causes leaf spot and rot diseases, which are responsible for yield losses of many economically important crops, including rice ( Oryza sativa ), wheat ( Triticum aestivum ), maize ( Zea mays ), sorghum ( Sorghum bicolor ), cotton ( Gossypium hirsutum ), aloe ( Aloe vera ), and kiwifruit ( Actinidia Chinensis ) [19,20,21,22]. At present, a few mycoviruses have been characterized from N. oryzae , including a novel partitiviruses [23] and a fusarivirus [24].…”

Genome Sequence Resource for Nigrospora oryzae, an Important Pathogenic Fungus Threatening Crop Production

“…2 aestivum), sorghum (Sorghum bicolor), cotton (Gossypium spp. ), and other crops (Fakhrunnisa et al 2006;Hajano et al 2011;Jagdish et al 1985;Palmateer et al 2003;Paul et al 1982;Prasad et al 1960;Sharma et al 2013;Standen 1945;Sun et al 2020;Zhai et al 2013;Zhang et al 2012;Zheng et al 2012;Zhong et al 2016;Wu et al 2014). The damaging impact of N. oryzae-caused diseases on agricultural production has been noted in the literature for over 70 years (Standen 1945).…”

Estudio de <i>Potyvirus</i> y <i>Nigrospora oryzae</i> como agentes patógenos del género <i>Calibrachoa</i>

“…Suele afectar plantas debilitadas por causas nutricionales y climáticas o por enfermedades o insectos (Sempere y Santamarina, 2008). Produce áreas circulares cloróticas en las hojas que se expanden y oscurecen con el avance del tiempo (Zhang et al, 2012). A su vez, puede causar lesiones en las puntas de las hojas que, en infecciones graves, se unen con las manchas circulares y, consecuentemente, provocan la muerte foliar (Zhai et al, 2013).…”

“…Sus estructuras de reproducción asexual -conidios-son negros, esféricos y unicelulares, y pueden visualizarse como signo de las lesiones de la superficie abaxial de las hojas (Zhang et al, 2012). Este hongo patógeno puede sobrevivir en las zonas infectadas de la planta, que son la fuente de inóculo para una próxima infección.…”

“…Esto coincide con lo indicado por Zhang et al (2012), donde los síntomas de este patógeno aparecieron luego de 5 días de la inoculación en plantas de Gossypium hirsutum (algodón). También Borrelli et.…”