Seed size and adventitious (nodal) roots as factors influencing the tolerance of wheat to waterlogging

In a glasshouse study, two experiments were conducted to understand how inherent variability, such as the seed size or mass, and formation of adventitious nodal roots might influence the tolerance of various wheat and triticale cultivars at different growth stages to waterlogging. Waterlogging at germination resulted in 11% seedling mortality, but the waterlogged seedlings had a 19% increase in shoot mass per plant, with no difference in root mass compared with non-waterlogged seedlings. Waterlogging at the 3-leaf stage was deleterious to only a few cultivars. On average, larger seed resulted in greater plant growth for most of the cultivars, and seed mass was positively related to the plant biomass and adventitious nodal root mass under waterlogged conditions. A decreasing oxygen concentration with increasing duration of waterlogging and soil depth did not affect the plant growth and visual stress symptoms, chlorosis, until the oxygen concentration decreased to less than 10% in the bottom depths. The highest yielding triticale cultivar, Muir, and wheat cultivars Brookton and Frame had the greatest seed mass, plant biomass, and relative growth rates under waterlogged conditions, compared with the lowest yielding wheat cultivars, Amery, Silverstar, and More. However, the degree of 'waterlogging tolerance', expressed as the percent ratio of plant biomass or growth rates under waterlogged conditions relative to the non-waterlogged control conditions, appeared to be greatest for the low-yielding cultivars, indicating a 'cautious approach' when screening tolerant cultivars.