First report of yellow stunt and root rot of standing milkvetch caused by Embellisia sp. from China

Yanzhong Li* and Zhibiao Nan

 College of Pastoral Agriculture Science and Technology, Lanzhou University, Gansu Pasture Ecological Research Institute, Lanzhou 730020, China

*E-mail: li_yanzhong@163.com

Accepted for publication 19/02/07

Standing milkvetch (Astragalus adsurgens Pall.) is important perennial forage in China. A new disease occurred severely in Huan County, Gansu Province (northern China) in 2004–2006. Symptoms were characterized by yellowing and necrosis of leaf blades, brown lesions of petioles (Fig. 1), discoloration of stems from brown to black (Fig. 2), overgrowth and stunt of shoots (Fig. 3, left side), root and crown rot, and plant death. Healthy plants were free from these symptoms (Fig. 3, right side).

Figure 1: Yellowing and necrosis of blade bases and brown lesions of petioles

A fungus was observed intercellularly and was consistently isolated from symptomatic tissues and seeds. The fungus was identified as Embellisia sp. (Simmons, 1971, 1983), but it differs from all described Embellisia species. Specimens of diseased plants and fungal isolate (MHLZU 0408) were deposited in the Mycological Herbarium of Lanzhou University.

Figure 2: Discoloration of stems (brown)

Pathogenicity was confirmed with three methods of spraying, wounded root and seed inoculation, respectively with 75-day-seedlings, 35-day-seedlings and seeds that were pre-germinated for 2 days. Plants grown in pots containing disinfested soil were maintained in a greenhouse where the temperature was 23±2 ^OC. The symptoms exhibited on inoculated seedlings and seeds were similar to those observed in the field, and the fungus was reisolated from inoculated plants. Untreated seedlings remained asymptomatic.

Figure 3: Diseased plants (left, showing overgrowth and stunt of shoots) and healthy plants (right)

This is the first report of yellow stunt and root rot of standing milkvetch caused by Embellisia sp. Some similar symptoms were previously observed in fields in Inner Mongolia of China (Hou and Bai, 1986; Hou, 2003). However, only in the present study were Koch’s postulates fulfilled and preliminary identification of the pathogen achieved. The disease causes serious degradation of standing milkvetch pastures.

References

Hou TJ. 2003. Forage disease and their control in Inner Mongolia. In: Nan ZB, Li CJ, eds. Forage and turfgrass pathological research in China. Beijing, China: Ocean Press, 11–17.

Hou, TJ, Bai R, 1986. Astragalus adsurgens diseases in Inner Mongolia and western Liaoning Province. Grassland of China 2, 40–43.

Simmons EG. 1971. Helmonthosporium allii as type of a new genus. Mycologia 63, 380–386.

Simmons EG. 1983. An aggregation of Embellisia species. Mycotaxon 17 216–241.

The British Society for Plant Pathology