International Research Highlights: 2018
Investigation of a devastating new disease of corn in Eastern Africa
By: Ben E. Lockhart, Professor, Department of Plant Pathology, University of Minnesota, and Roy Kiambi, Research Technician, Kenya Agricultural and Livestock Research Organization
Maize Lethal Necrosis (MLN) disease, a mixed infection by Maize chlorotic mottle virus (MCMV) and Sugarcane mosaic virus (SCMV), was first reported and was identified as MLN in Kenya in 2011. The disease spread rapidly to neighboring countries and by 2013 was identified in Rwanda, Uganda, Ethiopia and Tanzania. The effect on crop yield was significant and posed a serious threat to food security in this area where maize constituted 80% of the staple food. As a result, the Stakman-Borlaug Center for Sustainable Plant Health (SBC) worked in partnership with the Kenya Agricultural Livestock Research Organization (KALRO), the International Maize and Wheat Improvement Center (CIMMYT), the International Institute of Tropical Agriculture (IITA; Nigeria) and the United States Department of Agriculture and The Ohio State University (USDA/OSU) on a project financed by the Bill and Melinda Foundation to study the epidemiology of the disease and develop disease management strategies aimed at minimizing the effects of the disease on food security.
Significant conclusions were that MCMV infection was the primary driver in field infection and crop loss, and that the disease had not been recently introduced but had been in the area for some significant amount of time and was spread by infected seed. In addition, the emergence of a new vector corn thrips, with much higher population densities and reproduction rates in contrast to the previous known vector, corn rootworm, contributed greatly to the impact of the disease in the field.
The current collaboration between the SBC, Department of Plant Pathology and KALRO is focused on determining the modalities of seed and water transmission in order to identify cropping practices that will reduce disease infection. CIMMTY activities are focused on developing disease-resistant varieties, while USDA/OSU is working on the detection techniques of corn seeds.
International research on wheat stem rust
Wheat stem rust is a re-emerging disease, posing a significant threat to wheat production worldwide. The occurrence and spread of races in the Ug99 race group in East Africa, coupled with other races causing severe epidemics and localized outbreaks in Ethiopia, Europe, and Central Asia, is evidencing a strong comeback of this devastating disease. The Department of Plant Pathology and the USDA-ARS Cereal Disease Laboratory have been heavily involved in international stem rust research aiming to reduce vulnerability of bread and durum wheat to stem rust. We are part of an international surveillance system to detect and monitor the occurrence and spread of current and new virulent races of the stem rust pathogen. We have been actively participating in monitoring the development and spread of races in the Ug99 group and in characterizing races responsible for local epidemics and outbreaks in Ethiopia, Germany, and Kazakhstan. Partnering with several national and international research institutions, we have also been playing a leading role in improving the basis of stem rust resistance by identifying, characterizing and mapping new genes effective against Ug99 and other highly virulent races. Every year, thousands of bread and durum wheat entries are evaluated for stem rust resistance at the BSL-3 facility in St. Paul campus and in field nurseries in Ethiopia and Kenya. In addition to our research collaboration, in Ethiopia, we have been playing a critical role in capacity building, including training of Ethiopian young scientists and assisting in the establishment of disease screening centers and a race-typing laboratory.