Integrated management of Orobanche crenata in faba bean in Ethiopia

Broomrape (Orobanche crenata) is a major constraint to faba bean (Vicia faba) production particularly in northern Ethiopia. Few resistant faba bean varieties are capable of reducing the level of damage from O. crenata infestation in faba bean. There is therefore a need to enhance the level of productivity of resistant varieties through the adoption of management options that can be used in combating the parasitic weed problem in Tigray. Thus, the study was conducted July to December 2015 with the objective of evaluating the synergistic effect of host plant resistance, bio-inoculant (Rhizobium legimunosarum) and a bio-control agent (Trichoderma harzanium) on the severity of O. crenata and seed and biomass yield of faba bean varieties. Four faba bean varieties including one resistant variety and a local check, and a bio-inoculant (Rhizobium legimunosarum) and a bio-control agent (Trichoderma harzanium) were applied singly or in combination to treated plots. Uninoculated plots with neither of the inoculants were considered as control. The experiment was arranged in randomized complete block design with three replications. Data were collected from each plot and included days to Orobanche emergence, faba bean seed and biomass yield, number of emerged Orobanche shoots per m2, O. crenata biomass per plot, days to crop maturity and thousand seed weight. Bio-inoculation with R. leguminosarum and T. harzanium singly or in combination resulted in significant grain yield improvements in faba bean. The faba bean grain yield for the different treatments of the Orobanche resistant variety “Hashenge”, inoculated with both R. leguminosarum and T. harzanium, had yield advantage of 1012%, 527%, and 727% over Walkie, Moti and the local variety, respectively. Variety Hashenge treated with both inoculants had yield advantage of 29% over the control, uninoculated Hashenge, but only 13 and 9% yield advantage over the same variety singly treated with T. harzanium and R. leguminosarum, respectively. The yield difference between the Trichoderma harzianum+ Rhizobium treated and untreated showed significant yield differences of 36%, 44%, and 55% for varieties Walkie, Moti and the local variety. The current study has demonstrated that the combination of the right resistance type with the application of both R. leguminosarum and T. harzanium can improve plant growth and both biomass and seed yield of faba bean.