First confirmed report of sugarcane common rust (Puccinia melanocephala) in Ethiopia

In March 2007, researchers at the Ethiopian Sugarcane Research Services Station observed a ‘new’ disease in fields of sugarcane variety DB377/60. Symptoms presented as brown leaf streaks on affected cane in three out of eight fields grown with the variety.Disease incidence of more than 87 %, and disease severity above 9 %, were recorded using the indices developed by Chiarappa (1971).

Infected leaves were sent to the Global Plant Clinic for analysis (Fig. 1). Rust pustules were observed rupturing through the epidermis on the underside of the leaves (Fig. 2).Uredinia were elongate, reddish-brown, with capitate, hyaline to light brown paraphyses. Urediniospores were thick-walled, orange-brown, obovoid, measuring 26-34 x 16-20 µm. The urediniospore surface was echinulate with 4-5 equatorial pores. Teliospores were dark brown and measured 30-43 x 17-23 µm, clavate, two-celled and slightly constricted at the septum. The morphological characteristics fitted the description of Puccinia melanocephala (Virtudazao et al., 2001). A sample has been placed in the dried reference collection of CABI Bioscience UK Centre (IMI 395190).

Sugarcane(Saccharum officinarum) is a major host for P. melanocephala which has also been recorded on wild sugarcane(S. robustum and S. spontaneum) and the closely related Erianthus spp. To our knowledge this is the first confirmed record of P. melanocephala infecting S. officinarum in Ethiopia, although it has been reported from fifteen other African countries (including the bordering countries of Kenya and Uganda), and occurs in many sugar-producing countries throughout the world (CAB International, 2007).The recent discovery in Ethiopiais perhaps surprising given the distribution of the disease in Africa and the dispersal capabilities of rust spores. Indeed, the introduction of sugarcane rust into the Americas is believed to have occurred via the transoceanic transport of spores from Cameroon (Purdy et al., 1985). The neighbouring countries of Somalia and the Sudan should be vigilant, as the rust has not been confirmed from these regions. When the rust spread to the New World in the 1980’s it caused significant losses in susceptible varieties (J. Waller, pers. com.). Indirect costs can also be incurred as varieties are frequently withdrawn from commercial production because of susceptibility to the rust.