Drought tolerant corn hybrids
Several major seed companies have recently introduced corn hybrids that specifically target enhanced drought tolerance. Optimum AQUAmax hybrids from DuPont Pioneer and Agrisure Artesian hybrids from Syngenta were commercially available last year. In 2013, Monsanto is conducting a “stewarded” commercial introduction of Genuity DroughtGard hybrids in several Western Corn Belt states.
Most seed companies generally provide drought tolerance ratings for the hybrids they market (e.g. 1= poor; 9= excellent) but the recently introduced AQUAmax, Artesian and DroughtGard hybrids represent an effort to develop hybrids with traits affecting response to water stress. DuPont Pioneer and Syngenta drought tolerant hybrids involve native traits and those from Monsanto involve a transgenic trait. The companies marketing these hybrids emphasize that the enhanced drought tolerance associated with these hybrids is not associated with “yield drag”.
The hybrids are primarily targeted for use in the Western Corn Belt especially in areas where corn growers are looking for ways to reduce irrigation and conserve water supplied by aquifers. Nevertheless AQUAmax and Artesian hybrids adapted to Eastern Corn Belt conditions are available and Ohio growers had an opportunity to assess the performance of these hybrids during the 2013 drought.
Unlike Bt insect or herbicide resistant traits which involve single gene qualitative traits, drought tolerance is more complex and involves many genes. Some of the physiological traits associated with improved drought tolerance include a short anthesis silking interval (ASI, the time between the onset of pollen shed and silk emergence), delayed leaf rolling and senescence (leaf greenness), reduced barren and nubbin ears, better ear fill (greater kernel set and reduced abortion under stress), improved root development and architecture and photosynthetic/transpiration rates under stress.
A corn crop may be subjected to different types of drought stress - droughts may be protracted and season long in duration, or they may be limited to one or more developmental stages ( early to late vegetative growth, early and late grain fill). High temperatures in conjunction with drought during one or more of these stages can magnify the impact of stress. Hybrids may react differently to the varied types of drought stresses. Moreover drought tolerance may be strongly influenced by management practices. Greater corn plant populations promote more stressful conditions, and delayed and late planting dates often result in drier and hotter weather during critical development stages (i.e., flowering, grain fill).