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

Abstract

In Ethiopia, Fusarium ear rot (FER) reduces yield, quality and safety of maize, and negatively impacts economics of maize growers. However, there is almost no published information on geographic distribution, severity or causal agents of FER in Ethiopia or levels of preharvest fumonisin contamination, biophysical factors, and agronomic practices associated with FER. Therefore, we conducted a survey of 480 agricultural fields located in 10 Ethiopian zones to assess incidence and severity of FER as well as agricultural practices and biophysical factors associated with each field. We also determined the concentration of fumonisin in samples taken from the fields. Results revealed that FER was prevalent with varied disease intensity and yield loss levels among the assessed zones. The highest percent severity index (PSI) was recorded in Mirab Wellega (33.2%), with correspondingly maximum estimated mean yield loss of 13.6% while, the minimum disease severity 11.3% and yield loss 5.4% was recorded from Ilubabor zone. Fumonisins (FB1, FB2, FB3, & FB4) were detected in 98% of the samples and levels ranged from 5 μg kg−1 to 7517 μg kg−1 (mean, 540 μg kg−1 & median 82.4 μg kg−1). Mean fumonisin contamination of 1524.4, 1316.8, 744.5 & 742.6 μg kg−1 were recorded for Mirab Welega, Misraq Wellega, Assosa and Hawassa 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 (>1000 μg kg−1), and are not suitable for human consumption. Disease severity highly significantly (P<0.0001) correlated with biophysical factors such as insect infestation (r = 0.60, P<0.0001) and weed infestation (r = 0.64, P<0.0001), and agronomic practices such as NPS fertilizer application rate (r = ‐0.39, P<0.0001) and insecticide spray frequency (r = ‐0.55, P<0.0001). Other agronomic practices such as earlier or later sowing date, inter‐cropping systems significantly reduced (P<0.001) FER incidence, PSI and the associated grain yield loss. There was significant (p<0.0001) variation among maize cultivars currently under production in reaction against FER disease intensity. Moreover, the result of the present study attests a strong positive association (P<0.001) between disease intensity and maize fumonisin concentrations. Generally, the study revealed a wider distribution of FER and fumonisin contamination of maize in the South west major maize growing belts 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 and the associated mycotoxins in Ethiopia.This article is protected by copyright. All rights reserved

Comprehensive diallel analysis of combining ability and heterosis to Fusarium verticillioides ear rot resistance in maize

“…Maize resistance to FER is influenced by both the weather conditions during the flowering and post-inoculation periods (Deressa et al, 2023;Maschietto et al, 2017) and genotype × environment interactions (Mukanga et al, 2010); thus, highly resistant lines may be susceptible to FER in special environments. In the present study, Do123 and Jing64 exhibited high resistance in 12 environments but were susceptible in the XX22.…”