No abstract

In October 2006, occurrence of a disease on soybean (Glycine max) was observed in Guangdong Province of southern China with symptoms resembling red crown rot (3,4). Reddish brown lesions girdled the basal stems with numerous reddish orange perithecia on the lesion surface. Roots became black and rotted and whole plants wilted and died. More recently, outbreaks of this disease were observed in several counties in Guangdong. Disease incidence reached as much as 80% on cv. Huaxia 3 in some fields, causing severe yield losses. Isolation was made from the edge of lesions on potato dextrose agar at 25°C. The fungus produced white, aerial mycelia and a burnt orange-to-dark brown submerged growth. Conidiophores were borne laterally on a stipe, terminating in a hyaline, globose vesicle measuring 4.0 to 13.0 μm in diameter. After branching from the stipe, the conidiophore continued to develop by forming two to three single-celled branches. These cells might give rise to two or three shorter branches (14.8 to 36.9 μm long) and phialides. The phialides were doliform, nonseptate, and measured 7.4 to 19.7 × 3.7 to 4.9 μm. Conidia were hyaline, cylindrical with one to three septa (mostly three septa), and measured 54.1 to 76.3 × 4.9 to 7.4 μm. Perithecia were orange to red, subglobose to oval or globose, 212.1 to 454.5 μm high, and 111.1 to 333.3 μm wide. Asci were hyaline, clavate, thin walled, long stalked, measured 121.0 to 200.8 × 11.5 to 25.6 μm, and each contained eight ascospores that became aggregated in the upper half of the ascus at maturity. The ascospores were hyaline, fusoid to falcate with one to three septa (mostly with one septum), constricted slightly at the septum, and measured 29.5 to 73.8 × 4.9 to 9.8 μm. The fungus was identified as Cylindrocladium parasiticum (teleomorph Calonectria ilicicola) (1,2). The beta-tubulin gene fragment sequences of three isolates were obtained (one sequence being GenBank Accession No. GU073284) and comparisons with GenBank showed 99 to 100% similarity with Calonectria ilicicola (EF159730 and AY725643). Pathogenicity was confirmed by inoculation of 2-week-old seedlings of cv. Huaxia 3 in plastic pots (10 × 9 cm) by drenching with a conidia suspension (105 conidia per ml). All inoculated plants showed similar red crown rot symptoms on stem bases and roots 1 week after inoculation. C. parasiticum was reisolated from the diseased plants, and many orange-to-red perithecia of Calonectria ilicicola were formed on the lesions 3 weeks after inoculation. This pathogen may pose a serious threat to >300,000 ha of soybean production as well as >300,000 ha of peanut production in Guangdong Province. It has been previously reported in Jiangsu Province in eastern China (3) and Yunnan Province in western China (4). 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) J. Y. Gai et al. Soybean Sci. (in Chinese) 11:113, 1992. (4) Z. H. Ma et al. Plant Pathol. 53:537, 2004.

In June 2009, disease symptoms on peanut (Arachis hypogaea) were observed in several fields in Huoping county, Guangdong Province. The characteristic symptoms were black rot of the basal stems and roots, with many orange-brown fruiting bodies on the diseased parts. Entire vines eventually wilted and died. The disease incidence reached as much as 30% in some fields, causing severe yield losses. A fungus was consistently isolated from the edge of lesions and grown on potato dextrose agar at 25°C. Mycelia were white and floccose. Conidia were cylindrical to oblong-ellipsoidal, hyaline, one-celled, and measured 3-15 · 1-5 lm. Perithecia were glabrous apart from a number of rhizoidal hyphae, ostiolate and with a neck. The asci were cylindrical, thin-walled, stalk 5-27 lm long, 101-161 lm tall and 10-15 lm in diameter, without discernible apical structures, not evanescent, eight-spored. Ascospores were uniseriately arranged, pale, globose to ellipsoidal, and 7-16 · 7-12 lm.

In 2003 and 2005, routine disease surveys were conducted in rice (Oryza sativa) fields in Artvin and Samsun provinces, Turkey. In total, 41 fields were sampled from four districts. Distinct symptoms consisting of brown to black lesions that expanded and girdled the sheath were observed in one of the five fields surveyed in the Yusufeli district (Artvin), and two in each of the series of eight, 12 and 16 fields surveyed in the Alaçam, Terme and Bafra districts (Samsun), respectively.Infected leaf sheaths were surface disinfected for one minute in 1% NaOCl, transferred to potato dextrose agar (PDA) and incubated at 25°C. Colonies of pure cultures on PDA were white at first and then turned light brown or brown with increasing age. Four days after sub-culturing, large numbers of round or oval shaped sclerotia formed on the surface of the PDA, completely covering the culture. The sclerotia were initially white, turning reddish brown to black upon maturity and measuring 276-597 (413) · 249-483 (352) lm (n = 50). Two nuclei per hyphal cell were observed when the mycelium was stained with a mixture of Saffranin O and 3% KOH (Bandoni, 1979). Hyphal diameters ranged from 3AE2 to 7AE6 (5AE1) lm. The fungus was identified as Sclerotium hydrophilum based on its micro-morphology and cultural features (Cedeno et al., 1997; Aye et al., 2009).To satisfy Koch's postulates, four week-old rice sheath tissues (cv. Osmancık) were inoculated with 4 mm diameter plugs of five-day-old cultures on PDA that contained mycelium and sclerotia. Sterile, noncolonized PDA plugs were used as controls. The plugs were covered with parafilm and the plants were maintained in a greenhouse. Symptoms, similar to those originally observed in the field, began to appear on the leaf sheaths after 14 days at 25°C. No symptoms developed on control plants. The fungus was successfully re-isolated from the symptoms of artificially inoculated plants. Histological observations revealed brownish runner hyphae, and lobed hyphopodia were produced on the surface of infected leaf sheaths by S. hydrophilum. Sclerotium hydrophilum has been recorded previously on rice in Venezuela (Cedeno et al., 1997) 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 diseased parts. 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 151AE5-353AE5 lm and width 252AE5-404AE0 lm. 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 measured 2AE5-7AE4 · 29AE5-71AE3 lm. Isolation was made from basal stem tissues at the edge of disease lesions on potato dextrose agar (PDA) a...

The exit of Baise ship lift on the Right River is only about 700 m away from Dongsun Hydropower Station. Its dispatching operation, especially the unsteady flow, has a direct impact on the navigable water flow conditions of the approach channel gate area and river channel downstream of the Baise ship lift. According to some characteristics of Baise Junction and Dongsun Junction and the measured topography of Baoai River, a plane two-dimensional numerical model of the research river section is constructed, and the water flow changes in the mouth area under different working conditions are simulated and calculated. The research results show that the safety of navigation in the entrance area can be guaranteed from two aspects: optimizing the operation mode of the Baise and Dongsun cascade hydropower stations, and rationally formulating the downstream ship navigation management mode. Under the operating conditions of the four units of Baise Power Station, it is recommended that the ship wait for 0.5 h after the two units in Dongsun are started, so as to avoid the maximum water level increase period in the first half hour.