Crop improvement is dependent upon genetic diversity. The rate of genetic gain in breeding programs can increase by extending the amount or nature of variation available for selection using land races and wild relatives. However, exotic germplasm carries a range of undesirable traits, such as grain shattering, tall plant type, lodging, low yield potential, that limit their suitability for modern agriculture. Back-crossing to locally adapted varieties and pre-selection for traits is therefore required to ensure that meaningful data can be generated in field trials.
Multiparental schemes such as Nested association mapping (NAM) populations enabled to use exotic germplasm as a resource for the discovery of novel traits and QTL/genes. NAM combine the power of linkage analysis and the precision of association mapping. In NAM population development, founder lines are crossed with the same reference line to develop sets of related mapping progeny. When jointly analysed, NAM populations can provide higher power to detect QTL than in any of the constituent biparental families separately. NAM also have the advantages of association mapping of high diversity and resolution. Many historical recombination events between founders provides fine resolution as in association mapping allowing high resolution to localise QTL.
The program aim to develop a large NAM population using two Australian modern wheat varieties as reference parents and a diverse set of donor lines. Some of the donor lines are known for their tolerance to drought and heat, and nitrogen use efficiency.
Backcrossing and early plant culling will enable to avoid undesirable traits and generate populations amenable to modern agronomical practices.
The NAM population was generated by crossing 73 wheat accessions from the diversity panel from different continents and two Australian varieties, Gladius and Scout, as recurrent parents. Altogether the NAM population is composed of around 150 families, each of 20-24 lines to give a total population of over 3,000 BC1F4 derived lines.
All lines were genotyped using a targeted genotyping by sequencing approach. Families have been grown for two years in the field in different Australian growing regions and phenotyped with our UAV platform. Data will be used to identify loci associated to yield and grain protein content in Australian environment.
The parents of the NAM population will also be evaluated for disease resistance by Dr Manisha Shankar (DPIRD-WA) and for tolerance to drought in India by Dr Sigrid Heuer from Rothamsted Research as part of the TIGR2ESS project (https://www.globalfood.cam.ac.uk/keyprogs/TIGR2ESS). Dr Rhiannon Schilling from the University of Adelaide (https://researchers.adelaide.edu.au/profile/rhiannon.schilling) is also evaluating the NAM population for yield in regions of dispersive soils across Southern Australia.
More lines are available for specific families. If you are interested in our genetic material, please contact Melissa Garcia.
Langridge P and Fleury D (2011) Making the most of “omics” for crop breeding. Trends in Biotechnology 29: 33.