title: A rapid phenotyping method for adult plant resistance to leaf rust in wheat.
abstract: BACKGROUND
  Leaf rust (LR), caused by Puccinia triticina and is an important disease of wheat (Triticum aestivum L.). The most sustainable method for controlling rust diseases is deployment of cultivars incorporating adult plant resistance (APR). However, phenotyping breeding populations or germplasm collections for resistance in the field is dependent on weather conditions and limited to once a year. In this study, we explored the ability to phenotype APR to LR under accelerated growth conditions (AGC; i.e. constant light and controlled temperature) using a method that integrates assessment at both seedling and adult growth stages. A panel of 21 spring wheat genotypes, including disease standards carrying known APR genes (i.e. Lr34 and Lr46) were characterised under AGC and in the field.
  
  
  RESULTS
  Disease response displayed by adult wheat plants grown under AGC (i.e. flag-2 leaf) was highly correlated with field-based measures (R(2) = 0.77). The integrated method is more efficient-requiring less time, space, and labour compared to traditional approaches that perform seedling and adult plant assays separately. Further, this method enables up to seven consecutive adult plant LR assays compared to one in the field.
  
  
  CONCLUSIONS
  The integrated seedling and adult plant phenotyping method reported in this study provides a great tool for identifying APR to LR. Assessing plants at early growth stages can enable selection for desirable gene combinations and crossing of the selected plants in the same plant generation. The method has the potential to be scaled-up for screening large numbers of fixed lines and segregating populations. This strategy would reduce the time required for moving APR genes into adapted germplasm or combining traits in top crosses in breeding programs. This method could accelerate selection for resistance factors effective across diverse climates by conducting successive cycles of screening performed at different temperature regimes.
authors.affiliation: Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD 4072 Australia.
authors.forename: Adnan
authors.initials: A
authors.lastname: Riaz
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture, General Post Office Box 1600, Canberra, ACT 2601 Australia.
authors.forename: Sambasivam
authors.initials: S
authors.lastname: Periyannan
authors.affiliation: School of Agriculture and Food Science, The University of Queensland, St Lucia, QLD 4072 Australia.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Aitken
authors.affiliation: Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD 4072 Australia.
authors.forename: Lee
authors.initials: L
authors.lastname: Hickey
keywords: Accelerated growth conditions; Adult plant resistance; Disease screening; Leaf rust; Puccinia triticina; Wheat; Wheat breeding