Abstract:
Faba bean (Vicia faba L.) is an important food and cash crop in the highlands of South Wollo,
northeastern Ethiopia. Its production is increasingly threatened by faba bean gall disease
caused by Physoderma viciae. This study investigated the epidemiology of the disease,
characterized the causal pathogen, evaluated host resistance, and assessed integrated
management options during the 2022 and 2023 main cropping seasons. A total of 200 farmers’
fields were surveyed to determine disease prevalence, incidence, and percentage severity index
(PSI) in relation to agro-ecological and crop management factors. Pathogen characterization
combined symptom assessment, histopathological examination, cultural isolation, and molecular
detection using Physoderma-specific primers. Field experiments evaluated 28 faba bean
genotypes and four varieties × five fungicide treatments using randomized complete block
designs, with analysis of variance in R. Faba bean gall was widely distributed across all
surveyed districts. Prevalence, incidence, and PSI were higher in 2022 (97.41%, 74.81%, and
64.01%, respectively) than in 2023 (90.19%, 64.17%, and 47.21%, respectively), corresponding
with greater rainfall and relative humidity in 2022. Disease intensity increased with altitude,
particularly above 2,844 m a.s.l., and was highest at the flowering stage. Logistic regression
identified district, year, altitude, variety, previous crop, fungicide application, and field drainage
as significant determinants of disease development, with odds ratios and 95% confidence
intervals reported in the main text. Histopathological examination and molecular detection
confirmed P. viciae directly from symptomatic field tissues, whereas culture-based methods
yielded only saprophytic fungi. Among genotypes, Dosha, Obse, Wolkie, and FB-26869 showed
the lowest disease incidence, severity, and AUDPC values, while local varieties and genotypes
EH96048-1, EH00102-8-1, EH97091-2, and Gora were the most susceptible. Grain yield was
negatively correlated with disease parameters (r = −0.75 to −0.86) and decreased by 0.031–
0.040 t ha⁻ ¹ for every 1% increase in disease severity. Integrated management combining
moderately resistant varieties with fungicide application significantly reduced disease incidence,
severity, and AUDPC and increased grain yield. The combination of Dosha with Noble 25 WP
produced the highest grain yield (3.79 t ha⁻ ¹) and the highest net benefit (US$ 2,293.63–
4,168.20 ha⁻ ¹). In conclusion, faba bean gall is a major environmentally driven constraint to
faba bean production in South Wollo, with disease development strongly influenced by altitude,
moisture conditions, and host susceptibility. Integrated management involving moderately
resistant varieties, improved field drainage, cereal-based crop rotation, and timely fungicide
application is recommended for sustainable disease management. Future research should
prioritize DNA sequencing and phylogenetic characterization of P. viciae populations,
development of reliable inoculation techniques, breeding for durable resistance, and
improvement of disease forecasting systems to support sustainable faba bean production in the
highlands of northeastern Ethiopia