Evaluation of Corn Genotypes for Drought and Heat Stress Tolerance Using Physiological Measurements and a Microcontroller-Based Monitoring System.

Moisture deficit accompanied by high temperature are major abiotic stress factors that affect corn production in the southern United States, particularly during the reproductive stage of the plant.  In evaluating plants for environmental stress tolerance, it is important to monitor changes in their physical environment under natural conditions, especially when there are multiple stress factors, and integrate this information with their physiological responses. A low-cost microcontroller-based monitoring system was developed to automate measurements of canopy, soil and air temperatures, and soil moisture status in field plots. The purpose of the present study was to examine how this system, in combination with physiological measurements, could assist in detecting differences among corn genotypes in response to moisture deficit and heat stress. Three commercial hybrids and two inbred germplasm lines were grown in the field under irrigated and non-irrigated conditions in 2009 and 2010 at Stoneville, MS. Leaf water potential, photosynthetic pigments, cell membrane thermostability (CMT), and maximum quantum efficiency of PSII were determined on these genotypes under field and greenhouse conditions. In the month of July, under non-irrigated treatments, maximum canopy temperature among the genotypes ranged from 35-39⁰C, with air temperature as high as 40⁰C and soil water potential as low as -230 kPa. Variations observed in air and soil temperatures, and soil moisture in plots of the individual corn genotypes helped explain the genotypic differences in canopy temperature (CT), and these variations were reflected in the physiological responses. One of the commercial hybrids, having the lowest CT and the highest CMT, was the most tolerant among the genotypes under moisture deficit and heat stress conditions. These results demonstrated that the low-cost microcontroller-based monitoring system, in combination with physiological measurements, was effective in evaluating corn genotypes for drought and heat stress tolerance.