First Report of Cylindrocladium Black Rot of Peanut Caused by Cylindrocladium parasiticum (Teleomorph Calonectria ilicicola) in Jiangxi Province, China

Abstract

In July 2010, a serious disease of peanut (Arachis hypogaea) resembling Cylindrocladium black rot (CBR) was found in Longnan County, Jiangxi Province, China. Symptoms included chlorotic, yellowish and blighted leaves, and wilting of the plants. Taproots and hypocotyls were blackened and rotted. Clusters of reddish orange spherical fruiting bodies appeared in the lesions present on basal stems, pegs, pods, and roots of peanut. Disease incidence reached as much as 50% in some patches of the field. Plants with symptoms were sampled from fields. Microscopic examination revealed that the reddish orange, spherical fruiting bodies were the perithecia and measured 461.6 (337.5 to 609.4) × 395.5 (309.4 to 496.9) μm. With gentle pressure, asci and ascospores were exuded from perithecia. The asci were hyaline, thin walled, and long stalked. Ascospores were hyaline, falcate with one septum, and measured 43.5 (27.3 to 54.5) × 5.6 (4.1 to 6.8) μm with a length/width (L/W) ratio of 7.8 ± 1.3. A fungus with white-to-pale buff border mycelia and yellowish brown pigment was consistently isolated from the edge of basal stem lesions on potato dextrose agar at 25°C. Mycelia grew at temperatures ranging from 8 to 32°C and the optimum was 25 to 26°C. To determine the species, single-conidial isolates of the fungus were cultured on carnation leaf agar for 7 days at 25°C and 12 h of light/dark conditions. Conidia were hyaline, cylindrical with one to three septa (mostly three septa), and measured 49.3 (27.3 to 70.9) × 5.9 (4.1 to 6.8) μm with L/W ratio of 8.4 ± 1.6. Vesicles were globose and measured 5.5 to 10.9 μm in diameter. The fungus was identified as Cylindrocladium parasiticum (teleomorph Calonectria ilicicola) (1,2). A PCR assay was conducted on one representative isolate (JXLN32) by analyzing multilocus sequences of the TUB2 (coding β-tubulin protein), ACT (coding actin), and CaM gene (coding calmodulin protein) and were amplified and sequenced using the primers reported by Crous et al. (3). Sequences of the studied DNA regions were submitted to GenBank (Accession Nos. TUB2: JF429649; ACT: JQ070809; and CaM: JQ070808). BLAST searches with the existing sequences in GenBank showed that there was 99 to 100% identity with the existing sequences of C. ilicicola (GenBank Accession Nos. TUB2: AY725643; ACT: GQ280446; and CaM: GQ267402). To complete Koch's postulates, inoculum was prepared by mixing the microsclerotia (MS) suspension of the isolate (JXLN32) with soil at a proportion of 10 MS per g of soil. Ten replicate plastic pots containing five peanut seeds (cv. Yueyou 7) each were planted and placed in a glasshouse at 25 ± 2°C. The same number of peanut seeds was used as an uninoculated control. Typical basal stem and roots rot symptoms of CBR were observed in 2 months and C. parasiticum was reisolated from these inoculated diseased plants. No symptoms were detected on the control plants. To our knowledge, this is the first finding of Cylindrocladium black rot in Jiangxi Province, which is the main peanut-producing area in China. The disease has been previously reported in Guangdong Province in southern China but is not known elsewhere (4). Because of its ability to spread through seed and soil and its destructive potential, this pathogen may pose a serious threat to peanut production in China. References: (1) D. K. Bell and E. K. Sobers. Phytopathology 56:1361, 1966. (2) P. W. Crous et al. Mycol. Res. 97:889, 1993. (3) P. W. Crous et al. Stud. Mycol. 50:415, 2004. (4) R. Pan et al. Plant Pathol. 58:1176, 2009.

Two novel species of Calonectria isolated from soil in a natural forest in China

“…In agriculture, the Fabaceae and Arecaceae plant families are susceptible to infection by Calonectria species, including Ca. ilicicola, which causes black rot (CBR) of Arachis hypogaea (peanut) and Medicago sativa (Gai et al 2012, Pei et al 2015, Ca. ilicicola causes red crown rot of Glycine max (soybean) (Guan et al 2010), and Ca.…”

“…Based on previous studies, Calonectria species have been reported in nine provinces and one Special Administrative Region (SAR), which with the exception of LiaoNing and ShanDong Provinces belong to temperate regions (Luan et al 2006, Li et al 2010. Most Calonectria have been isolated from agronomic crops or forestry plantations in subtropical and tropical regions, including FuJian, GuangDong, GuangXi, GuiZhou, HaiNan, JiangXi and YunNan Provinces, as well as Hong Kong SAR (Crous et al 2004, Lombard et al 2010a, Chen et al 2011, Gai et al 2012, Pei et al 2015.…”

Diseases of Edible Oilseed Crops

“…In other parts of the United States, outbreaks of CBR have remained static, and yield losses are generally of secondary importance to other soilborne diseases. The first report of its occurrence with 50% incidence from the Guangdong Province in China has been made in (Pan et al 2009) followed by another first report of its occurrence from the Jiangxi Province in China in 2012 (Gai et al 2012). Depending on the age of plant at the time of infection, the effect of the disease can be devastating.…”

A phylogenomic tree of fungi: evolutionary relationships among Calonectria ilicicola and 586 fungal mitochondrial genomes

“…Calonectria ilicicola is a soil-borne fungal pathogen of global importance, which was first recorded in Georgia, the USA in 1965 and has since spread throughout peanut production areas in the southeastern United States (Bell and Sobers 1966;Wright et al 2010). CBR was first recorded on peanut in several counties in Guangdong Province in southern China in 2008, and subsequently observed on peanut in Jiangxi and Fujian Provinces, China, from 2010 to 2012 (Pan et al 2009(Pan et al , 2012Gai et al 2012). RCR was first recorded on soybean in Boluo County, Guangdong Province, China, and subsequently reported on soybean in Tonglu County, Zhejiang Province in eastern China in 2015 (Guan et al 2010;Gao et al 2012;Gai et al 2016).…”