QTL Associated with Waterlogging Tolerance and Related Physiological Traits in Wheat.

Waterlogging is a major constraint to crop yield worldwide.  In the soft winter wheat growing region of the eastern United States, yield losses as high as 30% have been observed in years with high rainfall during early vegetative growth.  It is also predicted that global climate change will result in increased winter precipitation and waterlogging of cereals.  Waterlogging causes an ‘energy crises’ due to the depletion of oxygen available to the plant for respiration, resulting in low ATP production.  Wheat has developed different mechanisms to adapt to waterlogging including both anatomical and biochemical changes.  Anatomical changes include the development of adventitious roots, aerenchyma and stem elongation.  Differences in physiological traits such as photosynthesis, chlorophyll content and stomatal conductance have also been associated with variation for waterlogging tolerance.  However, despite its impact on wheat yields, little is known about the genetic control of waterlogging tolerance.  In this study we report data from a set of 130 Jaypee/USG3209 RILs segregating in their agronomic and physiological response to waterlogging.  RILs were screened using a greenhouse waterlogging protocol where wheat seedlings were waterlogged for 28 days starting at 21 days after emergence.  Traits measured weekly included quantum yield and chlorophyll content (SPAD).  Following waterlogging both root and vegetative biomass were harvested and quantified.  Results showed that the two traits most affected by waterlogging were vegetative and root biomass, with reductions of 70% and 30% observed, respectively.  Tillering was also significantly reduced, with waterlogged plants having 17% less tillers compared to control.    A strong co-localization of QTL for flooding tolerance index (FTI), vegetative biomass, quantum yield and chlorophyll content was observed in the RIL population.  Other genome regions showed co-localization of QTL for FTI and root characteristics including root biomass and number of adventitious roots.  On-going work is focused on fine mapping of candidate QTL regions and field waterlogging of wheat cultivars and mapping populations.