2018 ASHS Annual Conference

The ability of plants to respond to disease causing pathogens by acquiring systemic resistance when exposed to those pathogens has been widely studied. Previous research with Arabidopsis has established that such acquired defenses can be even more pronounced in the progeny than the parental plant population, analogous to vaccinating a parent and seeing immunity in their children. The ability of weeds to similarly induce weed resistant crops has not yet been established. Plants can sense when other plants are close, a response referred to as shade avoidance, attributed to their response to red:far-red ratio of the light spectrum. Given that plants absorb the red-light spectrum for photosynthesis, far-red light spectrum is normally reflected. Consequently, there would be a lower red:far-red ratio in densely spaced plants such as a weedy environment compared to a non-weedy environment. This study aims to determine if these responses are heritable and can make the progeny more tolerant to weeds, without compromising their productivity. Greenhouse studies were started in 2015 at Rodale Institute and the University of Wyoming to determine if resistance to weed pressure is a heritable trait induced through competition in the F1 generation. The experiment was designed as a one by three factorial completely randomized block design replicated three times. Oat or wheat plants were planted in cone-tainers surrounded by annual ryegrass, redroot pigweed or soil (control). Test plant measurements of plant height, leaf length and width, and seed counts were taken on a weekly basis. At Rodale, F1 generation seed were saved and planted in the same environment as F1 generation. In Wyoming, saved F1 seed were factorially inter-planted in such a way that they had all possible combinations of weed/soil environments. Preliminary results from Rodale indicated that F2 oat plants exposed to ryegrass tended to be taller than controls. Preliminary results from Wyoming revealed that F2 progeny exposed to weeds or soil, whose parents were exposed to weeds, had 63% and 75% heading respectively while F2 progeny whose parents were not exposed to weeds had only 0% and 13% heading respectively. These results suggest that heading date in second generation wheat was influenced by previous generation's growing environment than current growing environment– implying that shade avoidance response to weed exposure is heritable.