Identification of tolerance to metribuzin and imazethapyr herbicides in faba bean. Issue 4 (7th June 2021) - Abou‐Khater, Lynn
Abstract: Weeds cause serious constraint to faba bean ( Vicia faba L.) productivity. Broad weed control is hampered by the availability of postemergence herbicides to control them, as the current faba bean cultivars are highly susceptible to them. Therefore, the deployment of postemergence herbicide tolerance is desirable in faba bean. To address this, 130 accessions were screened for their response in mature plants under field conditions to the recommended dosage of two herbicides, metribuzin at 250 g a.i. ha −1 and imazethapyr at 75 g a.i. ha −1 at Marchouch and Terbol stations. The recorded herbicide damage score (HDS) varied from 1 (no visual damage) to 5 (full damage with death of more than 50% of plants) at both locations. Low but highly significant ( p < .01) and positive correlation (+0.26) was obtained between the recorded HDS at both locations. Both herbicides significantly delayed flowering and maturity time occurrence, reduced plant height and grain yield, and increased number of branches. Reduction index (RI) correlated positively with HDS score at Terbol station in different seasons and at Marchouch in 2016–2017 seasons. Eleven tolerant accessions were identified and further evaluated to 1×, 1.5×, and 2× of recommended dose of both herbicides. The results indicated that the harmful effect of herbicides on grain yield reduction intensified from 13.4 to 27.2% and from −7.6 to 1.8% as the dose of metribuzin and imazethapyr increased respectively from 250 to 500 g a.i. ha −1 and from 75 to 150 g a.i. ha −1 . Tolerance to metribuzin and imazethapyr in eight faba bean accessions was confirmed with no significant reduction in grain yield. Core Ideas: Integration of faba bean in the cropping system increases its sustainability & soil fertility. The sources for herbicide tolerance will be combined with other traits to develop new cultivars. The identified lines reduce the cost of the production by limiting the laborious hand weeding. The identified new sources of herbicide tolerance in faba bean will be the first reported. Scope toward the development of postemergence herbicide tolerant faba bean cultivars.