Efforts of the government and development partners have stirred the interest of soybean production among farmers in Tanzania. The crop that is mainly cultivated for human consumption, utilization in animal feeds, soil fertility improvement and as source of income has increased in demand over the recent years.
Globally soybean rust poses a major threat to soybean production. Soybean rust (SBR), caused by a fungus- Phakopsora pachyrhizi, was first reported on soybean in Africa in Uganda, Kenya and Rwanda in 1996 and rapidly spread to several other countries in the continent. The disease that significantly reduces yields, is threatening soybean production in Tanzania. Information on its distribution, variability and potential spread through prevailing winds in Tanzania is not known. Through N2Africa support, field surveys were conducted in the major soybean growing regions of Tanzania namely: Ruvuma, Songea, Mbeya and Morogoro in the 2012-2013 growing seasons. Symptoms of SBR included yellowing of leaves and tan sporulating lesions. These symptoms were observed at flowering through seed maturity. From fields surveyed in 2012 and 2013, SBR was observed in 5 of 14 and 7 of 11 fields respectively. Incidence and severity ranged between 35 to 63% and 20-80% respectively. To confirm the pathogen, DNA was extracted from asymptomatic soybean leaf tissue and subjected to PCR analysis. The samples were confirmed positive of soybean rust. Fungicides are commonly used for controlling rust however they increase the cost of production and pose threat to the environment. Host resistance is considered as the best control option however, there are no resistant varieties available due to the variability of the fungus. Therefore, further studies to understand the virulence and genetic diversity of soybean rust population in Tanzania are on progress. Information from these studies will assist breeders deploy screen, and develop resistant germpalsm to the dominant rust populations in the country to help in controlling the disease in Tanzania. The first report of soybean rust in Tanzania was published in the Plant Disease Journal.
Harun Muthuri Murithi (Graduate Research Fellow) International Institute of Tropical Agriculture (IITA) & Wageningen University -Laboratory of Phytopathology. h.murithi@cgiar.org