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
Over the past years, ACPFG has identified a number of QTL for yield in dry environments in different Australian populations and repeated field trials. ACPFG has also identified QTL for tolerance to heat stress in greenhouse experiments, as well as in late sown field trials under irrigation. The Hub will validate these QTL in environments where drought and heat occur concurrently. To convert these technologies into “breeder ready” platforms, QTL will also be validated in diverse, adapted backgrounds and in different target environments by introgressing the QTL into Australian elite lines and field testing these new lines.
Subprogram 1.2. Novel traits and alleles for drought and heat tolerance
During reproductive development both heat and drought stresses reduce grain number and grain weight. This could be due to various processes, e.g., failed seed set could be due to pollen sterility, failed pollination or accelerated senescence. Tolerance mechanisms may conflict. For instance, evaporative cooling is a beneficial trait under heat stress, but excessive water loss causes drought stress in water-limited environments. Detailed knowledge of the molecular and physiological processes triggered by the combined drought and heat stress is therefore needed. The Hub will study a diversity panel of 300 wheats under combined stress to identify QTL with dual tolerance using association mapping.
Delphine Fleury (program 1 leader)
Nick Collins (subprogram 1.1 leader)
Penny Tricker (subprogram 1.2 leader)
Jessica Schmidt (PhD student)
Abdeljalil Elhabti (PhD student)
Fleury D, Jefferies S, Kuchel H, Langridge P (2010) Genetic and genomic tools to improve drought tolerance in wheat. Journal of Experimental Botany 61:3211-3222