Table 2

Annual rate of genetic gain in yield of wheat and rice varieties and maize hybrids in relation to year of release when grown without full control of biotic and abiotic stresses (with stress) or at yield potential levels (minimal stress)

Crop and regionPeriodRate of genetic yield gain, annual percentage rate
With stress Minimal stress
Bread wheat, NW Mexico1962–882.
Tropical rice, Philippines1966–951.00.800
Temperate maize
 Iowa, USA1967–911.20.9
 Nebraska, USA1983–9700
  • Rates of gain are linear in relation to year of release and therefore are computed separately in relation to the yield levels of the oldest and most recent (newest) releases. Yield potential with minimal stress has not changed in rice and maize during the period of study (13, 15, 17, 18).