Heterosis most often exploited in

Heterosis is most often exploited in Cross pollinated species.
cross-pollinated (hybrid) plants have “greater height, weight, and fertility” than their self-pollinated counterparts. The observation that cross-pollinated hybrids is more vigorous than their parents is nowadays commonly referred to as heterosis.
Heterosis describes the phenomenon in which hybrids formed between individuals of the same or closely related species are more robust or vigorous than their parents.
Thus, cross-pollinated species are often exploited.