In maize, heterosis is particularly evident and has been used commercially with great benefit. And also maize is a model system for the investigation of genetic and molecular basis of heterosis. Root systems of terrestrial plants serve many important tasks such as anchorage of the plant, uptake of water plus nutrients. Root performance also influence grain yield of maize directly or indirectly. To understand the genetic basis of heterosis for complex quantitative traits, it is a good choice to start from ro...