New soybean offers respite from deadly Asian rust

Asian rust-resistant TGx 1835-10E, at right, compared to a susceptible variety. Photo by IITA.
Asian rust-resistant TGx 1835-10E, at right, compared to a susceptible variety. Photo by IITA.

The Asian soybean rust is a fungal disease that is capable of laying waste as much as 80 percent of infested crops. This year, a soybean variety resistant to the disease that we developed was approved for release by the Nigerian National Variety Release Committee (NNVRC). The rust-resistant soybean is the first of its kind to be made available for cultivation not only in Nigeria but also in West and Central Africa.

Tagged TGx 1835-10E, our scientists bred the variety and further developed it in collaboration with the National Cereal Research Institute. Its release for general cultivation was approved in December 2008 and notified in June 2009 by the NNVRC.

Field trials in Nigeria showed that aside from being resistant to the Asian rust, the variety is also high-yielding, averaging 1655 kg/ha grain and 2210 kg/ha fodder. It is also early-maturing, has good promiscuous nodulation character, and resists pod shattering and other prevalent diseases.

The variety can be used for direct cultivation in tropical Africa or as a source of resistance genes in soybean breeding programs. It was previously released in Uganda through the initiative of Makerere University, a local partner, and has already shown excellent performance in trials carried out in Southern Africa, suggesting that it is well-adapted.

Its resistance is effective against all currently known types of the rust fungus in Nigeria. We have bred several other lines with rust resistance genes from various sources, which can be deployed quickly if this variety succumbs to newer forms of the rust fungus.

It was in 1996 that the Asian soybean rust first arrived in Africa, rapidly spreading through Uganda, Malawi, Mozambique, Rwanda, South Africa, Zambia and Zimbabwe. The disease was first noted in Nigeria in 1999.

The causal fungus of the Asian soybean rust, Phakopsora pachyrhizi, is very aggressive and can produce billions of spores capable of turning lush green crops with healthy foliage into brown fields with bare stalks in 2-3 weeks.

For most African farmers, using resistant varieties is the most viable method to control the disease as applying fungicides proves very costly.