A phenotyping platform for transgenic wheat: method and initial results

In recent years, the interest in new technologies for wheat improvement has increased greatly. As methods for conventional and molecular breeding have advanced, more efficient procedures for phenotyping have become a bottleneck. At the Australian Centre for Plant Functional Genetics (ACPFG), a centre for the improvement of wheat and barley's tolerance to environmental stresses, we developed a phenotyping platform for transgenic wheat and barley. After the initial selection of single/low copy number plants in the T0 generation, the T1 and T2 generation are screened under competitive growth conditions in large plastic bins. At present, the setup consists of 32 bins which can be used two times a year. All bins are fully equipped with irrigation system and sensors for soil water tension, soil temperature, air temperature, and air humidity, recording data at the time step of 5 minutes. The T1 generation is preferably grown in the summer season (January to June) whereas the T2 generation is evaluated in the main growing season (July to December). The first screening of T1 plants serves to remove off-types (for growth duration, plant height, and other growth anomalies) and to select homozygous plants. In the next step, T2 plants are phenotyped under different soil water and nitrogen regimes in a replicated experimental design in comparison with the wild type and null controls (drought and nitrogen response traits). Plant traits recorded in stage 2 for each individual plant were: tiller number, spike number, empty spikes, plant height, number of seeds, seed weight, and above ground biomass. The soil moisture tension curves of the drought treatments did show a gradual water stress increase over several days to weeks, closely mimicking field conditions. The observed average grain yields per plant were realistic for both well watered and droughted conditions, but seemed still to be too high under the low fertility regime. However, interpreting grain yield data from this setup remained difficult mainly because of the relatively high variability between replications. Further trials are needed to show if this variability can be reduced. We concluded that the new high throughput platform for the testing of transgenic wheat growing in a field-like situation but under controlled conditions was functioning. First season results showed that screening conditions for drought and nutrient use efficiency were as planned and that the platform served its objective. Improvements of the platform to achieve more homogenous results are outlined and the establishment of a digital imaging and analysis system is ongoing. These changes are intended to further increase the diagnostic value of the platform.