The increase in the traits of hybrid strength due to crossing over is called hybrid vigour or heterosis. The hybrid vigour in maize is exploited by crossing of an inbred parental line.
Related Theory
The explanation for heterosis phenomenon is based on ideas: (i) every trait of an organism depends on many genes. (ii) Inbreeding depression and heterosis are related to individual genetic diversity. The changes of individual genetic diversity caused by selfpollination and cross-pollination reveals that self-pollinating plants of natural crosspollinating leads to the decrease in individual genetic diversity of offspring and crossing between pure lines of genetic difference leads to the increase in individual genetic diversity. Thus, the decrease in individual genetic diversity is the cause the of depression and the increase in individual genetic diversity is the cause of heterosis.