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Ground Cover Supplement : GC Supplement - Wheat pre-breeding
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5 GROUNDCOVER Issue 127 | March – April 2017 | GRDC GROUNDCOVERTM SUPPLEMENT: WHEAT PRE-BREEDING EARLY SOWING ENVIRONMENTAL TAILORING Led by Dr Greg Rebetzke, CSIRO researchers identified six alternative dwarfing genes that can reduce crop stature without stunting coleoptile length and early growth. Dr Rebetzke says that this gene collection amounts to biodiversity that can be used to tailor height reduction and early growth properties for particular environments or agronomic practices. Field trials identified that a range of wheat heights can be achieved with the alternative dwarfing genes, including reductions that match those seen with the old dwarfing genes, and also shorter and taller statures (see Figure 1). Further more, grain yields, harvest index, grain number, grain protein concentration and nitrogen yield achieved with the alternative dwarfing genes generally matched the values seen with the existing dwarfing genes. In addition, Dr Rebetzke’s CSIRO colleague Dr Wolfgang Spielmeyer has identified a gene that actively promotes coleoptile length and it has been combined with the alternative dwarfing genes within Australian-adapted wheat. The resulting 24 lines underwent two years of intensive field testing at the GRDC’s Managed Environment Facilities at Yanco, Merredin and Narrabri within the southern, western and northern growing regions during 2015 and 2016. One clear outcome is a gain in the biodiversity available to adapt early wheat growth to different agro-climatic conditions. For instance, genes that strongly reduce wheat stature (such as the Rht-18 gene) were found to be better suited to maintaining yields in the wetter eastern wheatbelt, but had a negative effect on yields in drier environments, where weaker genes (such as the Rht-8 gene) are more suitable. Interest in the new wheat ger mplasm is growing among breeders, who have been consulted during its development and have hand-selected the material of greatest use to their breeding programs. To further assist adoption of the establishment trait into new varieties, molecular markers were developed that radically simplify selection of the new gene package. Markers are the preferred selection tool among breeding companies that have invested in high-throughput marker-assisted selection platfor ms. o GRDC Research Codes CSP00199, CSP00200 More information: Greg Rebetzke, 02 6246 5153, greg.rebetzke@csiro.au SOURCE: GREG REBETZKE, CSIRO FIGURE 1 Alternative dwarfing genes produced a range of reductions in plant height, including reductions similar to those achieved by the dwarfing genes present in Australian wheat varieties (Rht-B1b and Rht-D1b). Yanco Coleoptile length (mm) 120 100 80 60 40 20 0 Rht-B1bRht-D1bRht1Rht2Rht3Rht5Rht12Rht13Rht18TallsibsHalberdRht8(1)Rht8(2)Tall Narrabri Merredin Dr Greg Rebetzke PHOTO:BRADCOLLIS DRY SOILS AND EARLY DROUGHT By Dr Jairo Palta University of Western Australia n The trend towards declining early winter rainfall is especially noticeable in Western Australia, where it has been a steady trend for more than 100 years. As a consequence of this declining winter rainfall, wheat crops that are sown at the onset of autumn are exposed to increased risk of early season drought. This is exacerbated when wheat is sown dry – an increasing practice – with 82 per cent of wheat growers in WA now routinely sowing their whole crop dry. Wheat sown into dry soil will germinate on the first rainfall, potentially leaving crops vulnerable to 20 to 32 days of drought after emergence. While seedlings subjected to early drought often survive, their growth and development can be significantly slower, reducing biomass at flowering, duration of grain filling and grain yield. In severe cases, yield can be cut by half. Starting in 2012, and led by Dr Bob French of the Department of Agiculture and Food, Western Australia (DAFWA) Dryland Research Institute, initial trials were undertaken at the GRDC’s Managed Environment Facility (MEF) at Merredin, WA. A preliminary trial showed that wheat varieties experiencing a soil water shortage after emergence subsequently experienced delays in time to flowering of up to 20 days compared with the same varieties under irrigated conditions. Yields were found to vary between wheat varieties, indicating the existence of genetic diversity in the response to early drought. In 2015, a further and detailed trial was undertaken (also at the MEF in Merredin) to assess plant traits that could account for the variation in grain yield as a result of soil water shortage after seedling emergence. The traits evaluated were high leaf area under early-season drought and, upon recovery, tiller survival and time to anthesis (or flowering). The varieties MagentaA and EGA Bonnie RockA were found to be sensitive to the mild early-season drought, but
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