|AO, SAMADANGLA - University Of Minnesota|
|COULTER, JEFFREY - University Of Minnesota|
|RUSSELLE, MICHAEL - University Of Minnesota|
|VARGA, TAMAS - University Of Minnesota|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2020
Publication Date: 4/6/2020
Citation: Ao, S., Coulter, J.A., Russelle, M.P., Varga, T., Feyereisen, G.W. 2020. Drought tolerance in maize is influenced by timing of drought stress initiation. Crop Science. 60:1591-1606. https://doi.org/10.1002/csc2.20108.
Interpretive Summary: Climate changes include shifts in rainfall patterns that increase probability of growing season droughts for corn producers worldwide. To offset drought-induced loss of productivity, corn breeders have developed drought-tolerant hybrids. This experiment was performed to test yields of a drought-tolerant and a standard hybrid under drought-induced conditions with three rates of nitrogen fertilization and, if differences were found, to discover the physiological reasons for them. Three experimental conditions were tested: fully irrigated, drought stress induced 10 to 14 days before tasseling, and drought stress induced 10 to 12 days after tasseling. The three levels of nitrogen fertilizer applied were: less-than normal (50%), normal (100%), and greater than normal (150%) rates. Corn grain yields were 10% greater for the drought-tolerant hybrid when stress was applied 10 to 14 days before tasseling. However, there was no difference in grain yield between conditions of no drought stress (fully irrigated) and of drought stress induced 10 to 12 days after tasseling. When a greater than normal rate of fertilizer nitrogen was applied, grain and silage yields were 7 and 12% greater for the drought-tolerant than standard hybrid, respectively. Greater grain yield of the drought-tolerant hybrid when drought stress occurred 10 to 14 days before tasseling was associated with greater aboveground biomass, nitrogen uptake, and kernel number. The findings of this research will be of interest to producers/producer groups, seed companies, researchers, and agency personnel - all those with an interest in adapting our agricultural systems to changes in climate.
Technical Abstract: Maize (Zea mays L.) hybrids reported as having tolerance to drought are expected to perform better than non-drought-tolerant (‘standard’) hybrids under drought stress, but few studies confirm this with a mechanistic justification. Three experiments were conducted on loamy sand in central Minnesota in which drought-tolerant and standard hybrids were compared under three levels of sustained drought stress established using drip irrigation: no drought stress; drought stress from the 14-leaf collar maize phenological stage (V14) to maize physiological maturity (R6); and drought stress from the blister maize phenological stage (R2) to R6. Sub-optimal, optimal, or supra-optimal fertilizer nitrogen (N) rates were applied to each combination of hybrid and drought stress. Grain yield was 10% greater with the drought-tolerant than standard hybrid with drought stress from V14 to R6, but did not differ between hybrids when drought stress occurred from R2 to R6 or in the absence of drought stress. Grain and silage yields with the supra-optimal N rate were 7 and 12% greater for the drought-tolerant than standard hybrid, respectively. Kernel number and mass did not differ between hybrids in the absence of drought stress. With drought stress from R2 to R6 and V14 to R6, kernels per square meter were 6 and 23% greater and kernel mass was 3 and 10% less with the drought-tolerant than standard hybrid, respectively. Aboveground N uptake was 9% greater with the drought-tolerant than standard hybrid at the supra-optimal N rate, but did not differ between hybrids for the optimal and sub-optimal N rates. Greater grain yield of the drought-tolerant hybrid when drought stress occurred from V14 to R6 was associated with greater aboveground biomass, N uptake, and kernel number. Hybrids exhibiting such characteristics may have enhanced ability to tolerate sustained drought stress over a similar period of phenological development.