Erik Stokstad in Science:
In early summer, unusual pollinators swoop over rice fields in Texas and Arkansas. Small, nimble helicopters fly low and steady so their rotors blow pollen from one row of plants to another. The flights help RiceTec, a plant breeding company, produce seed for high-yielding, robust varieties of rice grown across the southern United States. It’s an expensive and complicated way to create seed.
But the effort is worthwhile because the seeds sprout into plants with a mysterious robustness and resilience. The phenomenon, called hybrid vigor, comes from crossing two strains of inbred parents. Why hybrids are superior to normal plants is not clear, but one long-standing hypothesis is that favorable versions of genes from one parent dominate poor-performing, recessive genes from the other.
The development of hybrid varieties has boosted the yield of maize, sorghum, and other crops by up to 50% and has resulted in other valuable traits, such as better drought tolerance. But the method is only feasible in some species; there’s no practical way to produce hybrid wheat or soybeans, for example. And when it works, it’s extremely labor intensive.