Response of Chickpea to Imidazolinone Herbicide.

Weed management in chickpea (Cicer arietinum L.) in Canada has been restricted by limited options of registered herbicides.  Only metribuzin and sulfentrazone are registered for use in chickpea in Canada.  The chickpea breeding program at the Crop Development Centre, University of Saskatchewan, has developed chickpea cultivars with tolerance to imidazolinone (IMI) class of herbicides. Two field experiments were conducted in 2012 at two locations in Saskatchewan, Canada. The first experiment was conducted to evaluate the response of two IMI tolerant cultivars and two conventional cultivars to different rates of imazamox (20 & 40g a.i/ha), imazethapyr (50 & 100g a.i./ha), and a combination of imazamox and imazethapyr (30 & 60g a.i./ha). The second experiment was conducted to examine the response of the same cultivars to IMI applications at multiple growth stages: 2-4 node, 5-8 node, and 9-12 node stage. For each experiment, visual injury ratings, leaf chlorophyll content, plant height and internode length were recorded at 7, 14, 21, and 28 days after each herbicide application (DAA). These measurements were used to derive a crop growth curve. Days to flowering, days to maturity, degree of branching, pods per plant, harvest index, and seed yield were additional measurements for elucidating physiological responses.  Visual injury ratings showed significantly lower rate in the tolerant cultivars than in the conventional ones. High injury rating in the conventional cultivars delayed days to flowering and days to maturity. Growth, in terms of height, was arrested until 21 DAA in conventional cultivars, contrasting no growth alteration in tolerant cultivars.  These experiments confirmed the tolerance of the selected cultivars to different rates of IMI herbicide applications. The tolerance to IMI in these cultivars is maintained across multiple IMI herbicide applications at different growth stages. These results open new options for broadleaf weed control in chickpea to include IMI herbicides.