The most important constraint to wheat production in Australia is water scarcity. In the last decade, Australia has suffered multi-year droughts and, based on FAO statistics, yield in 2006 dropped by 46% below the average 1960-2010 yield levels. Towards the end of the growing season, the risk of severe drought often coincides with high temperatures, further reducing yield and quality.
Average wheat yield losses due to heat stress in Australia have been estimated at 10-15%, a loss of $300M-400M per year. Heat stress during the heading stage most severely reduces floret fertility and thereby yield. Crop failures and yield reduction due to heat and drought stresses are predicted to increase due to increasingly variable climate and the frequency of severe weather events. It is therefore important to develop wheat varieties with tolerance to both stresses.
– Individual tolerance mechanisms can be “pyramided” into superior genotypes by marker-assisted backcrossing, a technique now routinely applied by breeders. Our first aim is to transfer known QTL and markers for breeding drought and heat tolerant Australian wheat varieties.
– Plant breeding is based on the use of genetic variation to generate new genetic combinations that lead to improved performance. Our second aim is to discover novel traits and allelic variations for the development of wheat with combined drought and heat tolerance using a diverse collection of germplasm.
Subprogram 1.1. Validation and transfer of known drought and heat QTL
Through extensive field trialling of Australian wheat populations in the former ACPFG, a number of QTL for yield in dry environments were identified. QTL for heat tolerance were also defined in greenhouse experiments.
The Hub is seeking to validate these QTL in field environments across Australia where drought and heat occur concurrently. The performance of the drought tolerance QTL is being assessed in the genetic backgrounds of a number of current Australian varieties, using backcross-derived lines.
Subprogram 1.2. Novel traits and alleles for drought and heat tolerance
Drought or heat stress individually reduce grain number, grain weight and final yields. The combination of the two stresses leads to more severe yield loss than either individual stress. By increasing our knowledge of the physiological processes triggered by combined drought and heat stress, we are identifying novel traits than can be measured to identify more tolerant wheats. Making use of advanced phenotyping platforms and tools, we are investigating plants’ water use, hydraulics and allocation of resources following drought and heat stress. We have also studied a diverse panel of 300 wheats under combined stress to identify QTL with dual tolerance using association mapping. We are making use of the new germplasm developed by the Hub to validate these novel alleles in Australian backgrounds.