January 19, 2003

A ProMED-mail post
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Source: Journal of Phytopathology, vol. 151 [edited]
RS Kawuki, E Adipala <acss@starcom.co.ug>, P Tukamuhabwa. Department of  Crop Science, Makerere University, PO Box 7062, Kampala, Uganda. Received 12 Jul 2002; accepted 9 Oct 2002

Studies were conducted to quantify yield loss attributable to soya bean rust caused by _Phakopsora pachyrhizi_, of soya bean (_Glycine max_), which is a new and emerging disease in Uganda. Data was collected from 3 consecutive seasons in the central, eastern, northern, and western parts of the country, using 3 commercial varieties (Nam 1, Nam 2, and Namsoy 3) and 2 elite varieties (UG-5 and GC-00138-29).

The commercial varieties recorded higher yield losses (26.9-36.3 per cent) and higher rust severities >50 per cent, whereas the elite varieties recorded lower yield losses of <10 per cent and rust severities of <30 per cent. Yield losses were highest in the central region of Uganda (22.9 per cent) and lowest in the northern region (15.1 per cent).

Yield losses differed significantly between seasons and were associated with reduction in seed weight and filled pod per plant.

Reference:
Kawuki RS, Adipala E, Tukamuhabwa P. Yield loss associated with soya bean rust (_Phakopsora pachyrhizi_ Syd.) in Uganda. J Phytopathol 2002; 151 (1): 7-12.

[This is apparently the first report of soybean rust in Uganda. Given the marked distinction between commercial and elite lines with regard to soybean yield, I asked Professor Adipala Ekwamu whether the elite soybean lines were essentially breeding lines for use in increasing yields, or were they lines to be used for commercial soybean production. He responded that elite lines UG-5 and GC-00138-29 were introduced as breeding lines. After satisfactory evaluation, these lines have been adopted in the breeding program to improve the 3 commercial varieties that are highly susceptible to rust. However, some soybean farmers in eastern Uganda have adopted them as suitable substitutes for the previous commercial varieties, which are being abandoned. - Mod.DH]

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