Physiological characterization of recent drought-tolerant maize hybrids at varying stress levels

Jason Roth, Purdue University

Abstract

Maize (Zea mays L.) is very vulnerable to moisture stress, especially when it occurs around the flowering period. Seed companies are increasingly developing drought-tolerant maize hybrids and promoting their use across geographies with varying climates (e.g. Western vs. Eastern Corn Belt). Few evaluations of these recent hybrids have been performed in the Eastern Corn Belt, and much is still unknown concerning their physiological mechanisms that may elevate tolerance to drought stress. This two-year study in northwestern Indiana attempted to characterize what physiological differences exist between similar-maturity drought-tolerant (non-transgenic) and non-drought-tolerant maize hybrids, as well as the impact of varied management practices (plant density – PD, and N rates) on these hybrids. AQUAmax™ (DuPont Pioneer) hybrids were compared to non-drought-tolerant hybrids at two PDs (79,000 and 104,000-109,000 pl ha-1) and four N rates (0, 134, 202, and 269 kg N ha-1). Grain yields (GYs) for the experiments averaged 11.2 Mg ha-1in 2011 (near normal precipitation), but only 7.4 Mg ha-1 in 2012, when extreme drought stress occurred from V12 into R1 stage (followed by frequent rainfall during grain fill). Overall leaf photosynthesis, transpiration, leaf chlorophyll content, and several other measurements of physiological differences between hybrids were minor; no clear pattern of drought-tolerant adaptive traits was discernible for the drought-tolerant hybrids in either year. Plant trait responses were often negative to increased PD (when significant) but positive to increased N rate (as expected). Hybrid by N rate and hybrid by plant density interactions; however, were generally non-significant. One drought-tolerant hybrid displayed lower leaf water transpiration that became more evident when using a cumulative season-long "scaling up" canopy approach. The same hybrid also exhibited slightly lower leaf area index, suggesting it may possess a drought-avoidance mechanism via water conservation. This may have proven beneficial had drought continued into the grain fill period. Unfortunately, this hybrid also exhibited greater anthesis-silking interval asynchrony both growing seasons—a generally detrimental trait with respect to drought tolerance. Total whole-plant N, P, and K nutrient uptake (2012) did not differ between comparable maturity drought- and non-drought-tolerant hybrids; however, nutrient harvest indices and internal efficiencies tended to be lower for the AQUAmax™ hybrids. Under the specific climatic conditions experienced each year, the drought-tolerant hybrids evaluated in this research did not demonstrate greater tolerance to stresses resulting from higher PD or lower N.

Degree

M.S.

Advisors

Vyn, Purdue University.

Subject Area

Agronomy|Plant sciences

COinS