A Self-Referencing Method for Selecting Heat-Tolerant Corn.

High-temperature is a major limiting factor for corn growth and development.  Current selection for heat tolerance is based on how the field-grown plants respond to high temperatures which may occur at different growth stages over years.   The objective of this research was to determine if changes in leaf chlorophyll fluorescence could serve as a self-referencing index for identifying heat-tolerant genotypes.  Six corn inbred lines were selected based on the field performance under high temperature environments in the west Texas.  Plants were grown in a greenhouse.  Leaf samples were collected at different growth stages from V-5 to V-12 stages and subjected to high temperature treatments.  Leaf chlorophyll florescence was measured.  Results showed that (1) 47°C appeared to be the best temperature to distinguish genotypes for heat tolerance, and (2) the genetic difference in leaf chlorophyll florescence under high temperature treatments varied with the plant growth stages.  Changes in leaf chlorophyll fluorescence at V-7 to V-8 stage may be related to plant response to the high temperatures in the fields.