EVALUATING WHEAT CULTIVARS FOR WATERLOGGING TOLERANCE

Waterlogging is a serious environmental stress on winter wheat (Tritic um aestivum L.) grown in the Gulf Coast region. We hypothesized that w aterlogging tolerance differs in currently available lines and cultiva rs and that suitability of physiological parameters to distinguish yie ld responses could be evaluated. Three types of studies were conducted : a 2-yr greenhouse study of eight cultivars, a 4-yr irrigated field s tudy of 20 cultivars and breeding lines, and a 3-yr field study of six cultivars under rain-excluding shelters which allowed comparison of p erformance under waterlogged and well-drained renditions. In the rains helter study, waterlogging caused a 45% decrease in grain weight, resu lting from a 45% decrease in number of kernels and a 5% decrease in ke rnel weight. Cultivars differed for grain yield under waterlogged cond itions in the field (P = 0.1), and Coker 9877 and line LA 862A16-3-3-X yielded 32 and 33% above the mean, respectively. Greenhouse measures of photosynthesis under waterlogging were weakly predictive of yield ( r(2) = 0.61) and correlated to measures under well-drained conditions (r(2) = 0.87). Yield was well correlated with biomass (r(2) = 0.84) an d root mineral content (Fe + Mn + P) (r(2) = 0.94). Waterlogged yields x cultivar did not correlate with yield under well-drained conditions (r(2) = 0.14) and the same differential response to waterlogging was shown for biomass and root mineral content. The negative correlation b etween root mineral content and yield was attributed to processes invo lved in the formation of a mineral plaque on the surface of the wheat roots. This emphasizes the need to explore differences in root functio n when selecting wheat lines for enhanced waterlogging tolerance.