Variation in Characteristics and Imazamox Tolerance of Feral Rye

Rye (Secale cereale L.) is a minor crop in America, with similarities to wheat (Triticum aestivum L.) in growth habit and distribution. However, feral rye has become a weed in wheat. Little is known about variation in feral rye morphological characteristics that influence success of cultural controls. Thus, 21 feral rye populations were sampled from wheat fields in central Oklahoma to characterize their morphology. Wide variation was found in characteristics that could favor perpetuation in wheat fields. Tillers per plant ranged from 1 to 19 and time to 50% spike emergence varied by 9 d. Mature height of the shortest and tallest spikes varied widely with almost all populations producing some spikes too short and too tall to be collected by typical direct harvesting. Lodging of stems at maturity ranged from 0 to 14%. Dormant seed varied from 0.3 to 3.9%. Variation in these and other morphological characteristics suggested a potential for differences in response to imazamox {2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-(methoxymethyl)-3-pyridinecarboxylic acid}. Mature spikes were harvested from 52 feral rye populations in Oklahoma. Seed from these feral rye populations as well as from popularly grown rye cultivars was individually planted. Mean leaf necrosis with imazamox at 27 and 54 g a.i. ha-1 applied to tillered plants was 66 and 89%, respectively. Necrosis of individuals varied from 0 to 100%. Among plants not controlled by imazamox, an exponential relationship in growth and reproduction suggested a wide range in herbicide tolerance.