Biophysical factors and agronomic practices associated with Fusarium ear rot and fumonisin contamination of maize in multiple agroecosystems in Ethiopia

Authors: DERESSA, TEMESGEN - Jimma University; GIRMA, ADUGNA - Jimma University; SURESH, L - International Maize & Wheat Improvement Center (CIMMYT); BEKEKO, ZELALEM - Ethiopia Haramaya University; Opoku, Joseph; Vaughan, Martha; Proctor, Robert; Busman, Mark; BURGUENO, JUAN - International Maize & Wheat Improvement Center (CIMMYT); PRASANNA, BODDUPALLI - International Maize & Wheat Improvement Center (CIMMYT)

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2023
Publication Date: 12/8/2023
Citation: Deressa, T., Girma, A., Suresh, L.M., Bekeko, Z., Opoku, J., Vaughan, M., Proctor, R.H., Busman, M., Burgueno, J., Prasanna, B.M. 2023. Biophysical factors and agronomic practices associated with Fusarium ear rot and fumonisin contamination of maize in multiple agroecosystems in Ethiopia. Crop Science. https://doi.org/10.1002/csc2.21159.
DOI: https://doi.org/10.1002/csc2.21159

Interpretive Summary: Corn is a major cereal crop that contributes to the food security and self-sufficiency of Ethiopia. One of the major limitations of corn production is Fusarium ear rot (FER) which is predominantly caused by the fungus Fusarium verticillioides. ARS scientists in collaboration with scientists at Haramaya University and Jimma University in Ethiopia and at CIMMYT in Kenya, conducted a two year (2020 and 2021) survey of 480 farmer fields located in 20 districts to determine the distribution of FER and how FER diseases varied across locations, and which agronomic practices were associated with FER in Ethiopia. Results revealed that FER was widespread, and districts with highest disease severity corresponded with highest yield losses. High insect infestation, high weed infestation, low nitrogen fertilizer application, and low frequency of insecticide spraying, contributed to high FER. Moreover, good agricultural practices such as early planting date, three round tillage, crop rotation, and inter-cropping systems significantly reduced FER and the associated grain yield loss in the study areas. The present study also confirmed the strong positive association of disease intensity with fumonisin contamination produced by F. verticillioides. This research is a first report of widespread occurrence of FER and high preharvest contamination of fumonisin in Ethiopian corn. The study further recommends use of integrated preharvest ear rot management strategies to control FER in Ethiopia.

Technical Abstract: Maize ear rots negatively impact yield, quality, safety, and economic gains of maize growers in Ethiopia. A survey was conducted in 2020 and 2021 growing seasons in 480 farmer fields located in 20 districts to determine the spatial distribution, fumonisin contaminations, biophysical factors, and other agronomic practices association with fusarium ear rot (FER) in Ethiopia. Results revealed that FER was significantly (p< 0.001) prevalent with varied disease intensity and yield loss levels among the assessed zones and districts. The highest disease severity was recorded in West Wallaga (33.19%), East Wallaga (29.45%), Hawassa (26.75%), and Jimma (22.91%) zones with correspondingly maximum estimated mean yield loss of 1.36, 1.29, 117, and 0. 99 %. Fumonisin (FB1, FB2, FB3, and FB4) was detected in 98% of the samples and levels ranged from 5 ug kg-1 to 7517 ug kg-1 (mean, 540 ug kg-1 and median 82.4 ug kg-1). However the concentration of AFB1, AFB2, AFG1, and AFG2 were below detectable level. Mean fumonisin contamination of 1524.4, 1316.8, 745.6, and 744.5 ug kg1 were recorded for West Wallaga, East Wallaga, Hawassa, and Jimma zones respectively. In total, about 11.3% of the maize samples exceeded the maximum tolerable total fumonisin limit set by the European Union in maize flour (>2, 000 µg kg-1), and are not suitable for human consumption. Disease severity significantly correlated with biophysical factors such as insect infestation (r=0.60) and weed infestation (r=0.64), and agronomic practices such as low-rate nitrogen fertilizer application (r=-0.39) and insecticide spray frequency (r=-0.55). Other agronomic practices such as early sowing date, three round tillage, crop rotation and inter-cropping systems significantly reduced (P <0.001) disease intensity (severity and incidence) and the associated grain yield loss in the study areas. This study confirmed a strong positive association (P<0.001) between disease intensity with contamination of different fumonisin groups (FB1, FB2, FB3, and FB4). The study also showed a wider distribution of FER and fumonisin contamination of maize in the major maize growing agro-ecologies of Ethiopia. Thus, appropriate integrated pre-harvest ear rot management strategies including the use of resistant cultivars and suitable agronomic practices are recommended for the management of FER disease and its associated mycotoxins in Ethiopia.