Chromosome Mapping of Post-Anthesis Heat Tolerance in Aegilops geniculata

High temperature stress after anthesis is detrimental to grain yield of wheat (Triticum aestivum, L). Wild relatives are a possible source of genetic diversity for tolerance in wheat.  TA2899, an accession of Aegilops geniculata (Roth), was previously identified as having tolerance to high temperature stress. This accession was also previously used to develop a complete set of chromosome addition lines in a Chinese Spring background.  The objective of this study was to utilize these genetic stocks to identify which chromosome(s) affect high temperature tolerance. Beginning 10 days after anthesis, the addition lines were screened in a high temperature growth chamber (35°C/30°C) for 16 days and compared to plants maintained at optimal temperature (25°C/19°C) for the same duration. Data collected during treatment included SPAD, Fv/Fm, days to flag leaf senescence, and days to physiological maturity. The 14 addition lines, Chinese Spring, two tolerant and two susceptible controls were tested in a completely randomized design with two replications. Four addition lines were observed to have significantly more days to flag leaf senescence than Chinese Spring and were similar to, or better than, the tolerant controls. One of the addition lines was substantially better than the tolerant controls for days to flag leaf senescence and likely contains a major QTL for high temperature tolerance. It, along with the other addition lines that appear to have improved tolerance to high temperature stress will be further tested in replicated experiments and used for targeted introgression into an agronomically desirable background.