In article from Science Daily, the growth of root hair is key to a plant pushing its roots further into the soil and not popping out of the soil.

“This ability is governed by a self-reinforcing cycle. A protein at the tip of root hairs called RHD2 produces free radicals that stimulate the uptake of calcium from the soil. Calcium then stimulates the activity of RHD2, producing more free radicals and further uptake of calcium. When an obstacle blocks the hair's path, the cycle is broken and growth starts in another location and direction.”

Have hard soil and/or low calcium soil, plan on a poor root system. Even the best genetics cannot over come hard or low calcium soil.