WATERLOGGING EFFECTS ON YIELD AND PHOTOSYNTHESIS IN 8 WINTER-WHEAT CULTIVARS

Winter wheat (Triticum aestivum L. emend. Thell.) yields in Louisiana are consistently below the national average because of a combination o f biotic and abiotic environmental factors prevailing in the Gulf Coas t region. This study was undertaken to estimate the yield loss for whe at that is attributable to soil waterlogging and to compare physiologi cal performance under waterlogging-stressed conditions by cultivars gr own in Louisiana. In a 3-yr pot study conducted in a greenhouse, water logging stress was imposed by raising the water level to the soil surf ace. This treatment reduced the soil redox potential in the pots from an average of 409 to 149 mV, indicating an absence of free oxygen in t he rootzone. Compared with a well-drained control treatment, grain wei ght was depressed 37 to 45% by waterlogging in the eight cultivars tes ted. In a field experiment with 'Coker 9877, grain weight was depresse d 51% in poorly drained plots compared with well-drained plots. Yield depression was due to reduced kernel number and kernel weight rather t han to an effect on stand establishment. In the greenhouse experiments , flag-leaf photosynthesis correlated well with grain weight in the cu ltivars tested. Waterlogging caused only it small suppression of flag- leaf photosynthesis and leaf conductance, and there were no significan t interactions between treatment and cultivar. These commercially avai lable cultivars showed an equally poor tolerance of waterlogging stres s. The results emphasize the need for identification of waterlogging t olerance in wheat cultivars developed for the Gulf Coast states.