New Disease Reports
New Disease Reports (2009) 19, 52.
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Cylindrocladium black rot caused by Cylindrocladium parasiticum newly reported on peanut in China

R. Pan 1,2*, M. Guan 2, D. Xu 2, X. Gao 1, X. Yan 1 and H. Liao 1

*panrq@scau.edu.cn

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Accepted: 01 Jul 2009

In June and October 2008, disease symptoms on peanut (Arachis hypogaea) were observed in several fields in Guangdong Province. The characteristic symptoms were black rot of the basal stems and the below-ground tissues including roots, pegs and pods, with reddish-orange fruiting bodies on the diseasedparts (Figs. 1, 2). Entire vines eventually wilted and died. The disease incidence reached as much as 50% in some fields, causing severe yield losses.

Microscopic examination revealed that the reddish-orange fruiting bodies were perithecia of height 151.5-353.5 μm and width 252.5-404.0 μm.The asci were clavate, thin-walled and long stalked. Ascospores were hyaline, fusoid to falcate, one- to three-septate, constricted slightly at the septum, and measured2.5-7.4 x 29.5-71.3 μm (Fig. 3). Isolation was made from basal stem tissues at the edge of disease lesions on potato dextrose agar (PDA) at 25°C. Conidia and microsclerotia (Fig. 4) were observed after three to four days. Conidiophores were borne laterally on a stipe, terminating in a hyaline, globose vesicle 4.5-13.0 μm diameter. Stipes arose at right angles from procumbent mycelia in culture; they were septate, becoming narrower towards the apex. Conidia were cylindrical and had one to three septa (mostly only one), measured 4.9-7.4 x 36.9-73.8 μm and budded terminally from the conidiophores (Fig. 5). Perithecia were formed in V8-juice medium after 20 days. The fungus was identified as Cylindrocladium parasiticum (teleomorph Calonectria ilicicola) (Bell & Sobers, 1966; Crous et al., 1993). Pathogenicity was confirmed by inoculation of two-week-old seedlings in pots of cv. Bendizhongby drenching the soil near to the shoot with a mixed suspension of mycelia, conidia and microsclerotia. All inoculated plants showed black rot symptoms on stem bases and rootstwo weeks after inoculation, and C. parasiticum was reisolated from inoculated plants.

Cylindrocladium black rot of peanut is a major disease in the United States (Branch & Brenneman, 2003). To our knowledge, this is the first report of this diseaseon peanut in China.This pathogen may pose a serious threat to peanut production in China where peanut is a major crop.

Figure1+
Figure 1: Black rot caused by Cylindrocladium parasiticum on basal stems of peanut, showing reddish-orange perithecia of the fungus
Figure 1: Black rot caused by Cylindrocladium parasiticum on basal stems of peanut, showing reddish-orange perithecia of the fungus
Figure2+
Figure 2: Black rot of peanut pods
Figure 2: Black rot of peanut pods
Figure3+
Figure 3: Ascus and ascospores of Cylindrocladium parasiticum
Figure 3: Ascus and ascospores of Cylindrocladium parasiticum
Figure4+
Figure 4: Microsclerotia
Figure 4: Microsclerotia
Figure5+
Figure 5: Conidiophore and conidia
Figure 5: Conidiophore and conidia

Acknowledgements

This work was supported by the National Key Basic Research Funds of China (Grant No. 2005CB120902).

References

  1. Bell DK, Sobers EK, 1966. A peg, pod, and root necrosis of peanuts caused by a species of Calonectria.Phytopathology56,1361-1364.
  2. Branch WD, Brenneman TB, 2003. Field resistance to Cylindrocladium black rot and tomato spotted wilt virus among advanced runner-type peanut breeding lines. Crop Protection 22, 729-734.
  3. Crous PW, Wingfield MJ, Alfenas AC, 1993. Cylindrocladium parasiticum sp. nov., a new name for C. crotalariae. Mycological Research 97, 889-896.
This report was formally published in Plant Pathology

©2009 The Authors