Abstract:
Chocolate spot (Botrytis fabae Sard.) is one of the major diseases menacing faba bean (Vicia faba L.)
production and restraining its productivity in Ethiopia and other African countries. The yield losses
reach up to 100% on susceptible cultivars. Although a number of faba bean varieties with good yield
potential have been released, their reaction to this major disease and yield performance are little
understood in southwest Ethiopia. Thus, chocolate spot epidemics on 13 improved faba bean
varieties were studied under natural infections at three sites varying in altitudes from 1805 to 2660 m
in the Dawuro zone of southwest Ethiopia. The field experiments consisted of 14 treatments (13
varieties and a local cultivar) are laid out in a randomized complete block design (RCBD) with three
replications (40 plants/plot) during the 2011/2012 crop season. The onset and progress of chocolate
spot severity was assessed (with a 1-9 scale) every seven days until the epidemic attained peak and
then grain yield and 100-seed weight were recorded and statistically analysed. The varieties varied
significantly (P < 0.001) in disease severity index, AUDPC and infection rates (r) values, grain yield and
100-seed weight. CS20DK, Degaga, Nc-58, Bulga-70, Tesfa and Kasa exhibited high to moderate
resistance to chocolate spot with consistently slow progression and terminal disease severity,
AUDPC- and r-values at all testing sites. The yield performance of CS20DK and Degaga were also
superior at Tocha and Turi while Nc-58 (2027 kg/ha) and Moti (1973 kg/ha) that showed susceptible
reaction gave good yield only at Tocha. This study indicated that improved faba bean varieties reacted
differently to chocolate spot infection and yield potentials across varying localities, and thus better
performing varieties such as CS20DK, Degaga and Nc-58 are recommended for faba bean production
in southwest Ethiopia
