Cheatgrass Inhibits Wild Potato (Solanum jamesii) Tuber Sprouts

Cheatgrass (Bromus techtorum) is an non-native grass that has invaded the natural range of the two wild potato species in the USA. We sought to detect evidence that it suppresses Solanum jamesii (jam). We grew flats of 12 cheatgrass populations and dried and stored the straw and the media containing the roots. In the following year, we again prepared flats of actively growing grass as well as flats with plain potting medium as control. One sprouted tuber of each of 35 jam populations was planted in flats of each of the 12 cheatgrass populations for each treatment: Control, Grass, Straw, and Roots. Percent shoots emerged in Root media treatment was not significantly different from Control, each at about 93%, but Grass (70%) and Straw (80%) were significantly lower than Control. The 12 cheatgrass populations inhibited jam tuber shoots compared to Control differently, as Grass (8% to 43% reduction) and as Straw (0% to 33% reduction). Subjective scores of the vigor of cheatgrass and emerged jam stands indicated that a more vigorous stand of cheatgrass is associated with less vigorous jam shoots. It appears that cheatgrass can significantly inhibit jam shoots from sprouted tubers even when growing in optimal conditions.