Ground Cover Supplement : GC Supplement - Statistics for Australian Grains
GROUNDCOVER 15 Issue 126 | Jan -- Feb 2017 | GRDC GROUNDCOVERTM SUPPLEMENT: SAGI QUALITY VALIDATION FAST FACTS n Valid experimental designs, in particular the replication and randomisation in all phases of the testing processes and appropriate statistical analyses, are vital to ensure the GxE investigation of key APH classification traits delivers sound results for growers. APH WHEAT EXPANSION PROJECT RAISES BAR ON DATA ANALYSIS By Clare Johnson, Daniel Tolhurst and Dr Alison Smith n Calls for the expansion of the Australian Prime Hard (APH) wheat zone into Victoria, South Australia and Western Australia have led to rigorous experimental design and analysis of genotype by environment (GxE) variation to determine whether grain produced in these zones can satisfy APH quality demands. APH wheat is currently zoned for segregation in Queensland and New South Wales, but heightened interest by Victoria, SA and WA has seen trials conducted across the wheatbelt over three years to determine whether the genetic traits required to produce APH grain will hold up in these environments. APH is an internationally recognised premium wheat grade, which requires at least 13 per cent protein on an 11 per cent moisture basis for APH2, or at least 14 per cent protein at 11 per cent moisture for APH1. APH wheat is in high demand and can attract a premium price. QUALITY To consider a change of zone the Wheat Classification Council (WCC) requires three years of rigorous scientific data to ensure that the grain produced will satisfy all the requirements for APH, which include not only protein, but also physical grain and milling, flour and processing functionality properties. This requires quantification of genotype by environment (GxE) interaction for a range of key quality traits for a specified set of varieties across a range of environments spanning the four classification zones. These traits are complex, making it difficult, if not impossible, to see clear effects of the varieties or the in-crop management, unless the laboratory process and the field trial are both taken into account in the design and analysis. Many past studies examining GxE for wheat grading traits have been flawed. Traits were typically measured using samples bulked up from all field replicates and without replication or randomisation in any of the laboratory processes. EXPERIMENTAL DESIGN The project team, which involved CSIRO and later Wheat Quality Australia (WQA), engaged Statistics for the Australian Grains Industry (SAGI) to use its multi-phase methodology to address the aims of the study. Multi-phase design helps to distinguish between genetic and non-genetic sources of variation when varieties are first grown in field trials (phase I); then grain samples are tested in the laboratory using one or more processes (phase II and higher). For the APH expansion project SAGI developed experimental designs that encompass replication and randomisation in all phases of the testing process to ensure statistical validity for the project while meeting budgetary and time constraints. Project analyses from the first two seasons showed at least some non- genetic variation in all trials. Sometimes this variation was quite substantial and its cause needs to be further investigated. Once the full three seasons of data have been analysed, findings such as these will help the WCC decide whether APH wheat quality can be produced outside the current classification zones. o GRDC Research Codes WQA00004, CFF00004 More information: Clare Johnson, GRDC, 0477 742 924, email@example.com; Daniel Tolhurst, University of Wollongong, 02 4221 3491, firstname.lastname@example.org; Dr Alison Smith, University of Wollongong, 0417 947 115, email@example.com SOURCE: CLARE JOHNSON FIGURE 1 APH wheat variety field sites. 2013 (10) Perth Albany Adelaide Sydney Brisbane Melbourne Geraldton 2014 (12) 2015 (14) Each year APH varieties are grown at between 24 and 32 field sites in both current and potential APH zones. Based on receival data a subset of these (see map above) are chosen for detailed functionality testing.
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