G. J. Rebetzke

Commonwealth Scientific and Industrial Research Organisation

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Anthony G. Condon

Commonwealth Scientific and Industrial Research Organisation

Richard A. Richards

Commonwealth Scientific and Industrial Research Organisation

R. A. Richards

NOAA National Marine Fisheries Service Northeast Fisheries Science Center

David Bonnett

Centro Internacional de Mejoramiento de Maíz Y Trigo

Scott Chapman

University of Queensland

John A. Kirkegaard

Commonwealth Scientific and Industrial Research Organisation

Michelle Watt

University of Melbourne

Marc H. Ellis

Centro Internacional de Mejoramiento de Maíz Y Trigo

Karine Chenu

Agriculture and Food

Graham D. Farquhar

Australian National University

Cooperative Institutions

Commonwealth Scientific and Industrial Research Organisation

175

Agriculture and Food

136

Plant Industry

111

Centro Internacional de Mejoramiento de Maíz Y Trigo

ACT Government

University of Western Australia

University of Queensland

Australian National University

University of Adelaide

University of Sydney

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Phenotypic variation and QTL analysis for oil content and protein concentration in bread wheat (Triticum aestivum L.)

Euphytica (2015)

Chris Moore Richard A. Richards G. J. Rebetzke

Germ plasm

Coefficient of variation

10.1007/s10681-014-1346-3

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Citations (16)

High Throughput Determination of Plant Height, Ground Cover, and Above-Ground Biomass in Wheat with LiDAR

Frontiers in Plant Science (2018)

José A. Jiménez-Berni David M. Deery Pablo Rozas Larraondo Anthony G. Condon G. J. Rebetzke

Crop improvement efforts are targeting increased above-ground biomass and radiation-use efficiency as drivers for greater yield. Early ground cover and canopy height contribute to biomass production, but manual measurements of these traits, and in particular above-ground biomass, are slow and labour-intensive, more so when made at multiple developmental stages. These constraints limit the ability to capture these data in a temporal fashion, hampering insights that could be gained from multi-dimensional data. Here we demonstrate the capacity of Light Detection And Ranging (LiDAR), mounted on a lightweight, mobile, ground-based platform, for rapid multi-temporal and non-destructive estimation of canopy height, ground cover and above-ground biomass. Field validation of LiDAR measurements is presented. For canopy height, strong relationships with LiDAR (r² of 0.99 and root mean square error of 0.017 m) were obtained. Ground cover was estimated from LiDAR using two methodologies: red reflectance image and canopy height. In contrast to NDVI, LiDAR was not affected by saturation at high ground cover, and the comparison of both LiDAR methodologies showed strong association (r²=0.92 and slope=1.02) at ground cover above 0.8. For above-ground biomass, a dedicated field experiment was performed with destructive biomass sampled eight times across different developmental stages. Two methodologies are presented for the estimation of biomass from LiDAR: 3D voxel index (3DVI) and 3D profile index (3DPI). The parameters involved in the calculation of 3DVI and 3DPI were optimised for each sample event from tillering to maturity, as well as generalized for any developmental stage. Individual sample point predictions were strong while predictions across all eight sample events, provided the strongest association with biomass (r²=0.93 and r²=0.92) for 3DPI and 3DVI, respectively. Given these results, we believe that application of this system will provide new opportunities to deliver improved genotypes and agronomic interventions via more efficient and reliable phenotyping of these important traits in large experiments.

10.3389/fpls.2018.00237

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Citations (262)

Wheat genotypes with high early vigour accumulate more nitrogen and have higher photosynthetic nitrogen use efficiency during early growth

Functional Plant Biology (2013)

Jiayin Pang Jairo A. Palta G. J. Rebetzke S.P. Milroy

Genotypic differences in early growth and nitrogen (N) uptake among 24 wheat (Triticum aestivum L.) genotypes were assessed in a field trial. At late tillering, large genetic variation was observed for shoot biomass (23–56 g m–2 ground area) and N uptake (1.1–1.8 g m–2 ground area). A strong correlation between aboveground biomass and N uptake was observed. Variation around this relationship was also found, with some genotypes having similar N uptake but large differences in aboveground biomass. A controlled environment experiment was conducted to investigate the underlying mechanisms for this variation in aboveground biomass using three vigorous genotypes (38–19, 92–11 and CV97) and a non-vigorous commercial cultivar (Janz). Vigorous genotypes had lower specific leaf N in the youngest fully expanded leaf than Janz. However, there was no difference in chlorophyll content, maximum Rubisco activity or the rate of electron transport per unit area. This suggests that Janz invested more N in non-photosynthetic components than the vigorous lines, which could explain the higher photosynthetic N use efficiency of the vigorous genotypes. The results suggest that the utilisation of wheat genotypes with high early vigour could improve the efficiency of N use for biomass production in addition to improving N uptake during early growth.

Ecophysiology

Photosynthetic efficiency

10.1071/fp13143

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Citations (85)

Improvement of the model capacity and assessment traits related with water use efficiency for wheat in Australia

Bangyou Zheng Karine Chenu M. Fernanda Dreccer Tingyu Duan G. J. Rebetzke

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Evaluation of reduced-tillering (tin) wheat lines in managed, terminal water deficit environments

Journal of Experimental Botany (2013)

J. H. Mitchell G. J. Rebetzke Scott Chapman S. Fukai

Small or shrivelled wheat kernels (screenings) that reduce crop value are commonly produced in terminal drought environments. The aim of this study was to establish whether the incorporation of the tiller inhibition (tin) gene would contribute to maintenance of kernel weight and reductions in screenings under terminal water deficit. Five Silverstar near-isogenic lines contrasting in high and low tiller potential and their recurrent Silverstar parent were established at two plant densities under managed terminal water deficit (mild and severe) and irrigated conditions. With irrigation (grain yield of 5.6 t ha–1), kernels of all lines weighed ~31mg, with restricted-tillering (R-tin) lines producing an average 15% lower grain yield. Under both mild and severe terminal water deficit (4.1 t ha–1 and 2.8 t ha–1), free-tillering lines had relatively high screenings ranging from 11.9% to 16.2%. Compared with free-tillering lines, R-tin lines maintained large kernel weight (~29mg kernel–1) and had 29% and 51% fewer screenings under the two stresses, and a significantly greater (+11%) grain yield under mild stress. Higher kernel weights in tin lines were realized even with the greater kernel number per spike. The higher kernel weight of the R-tin lines under stress conditions was associated with greater anthesis biomass and increased stem water-soluble carbohydrates, ensuring more assimilate for later translocation to filling grain. The incorporation of the tin gene into genetic material adapted to the target environments provides scope for improvement in both grain yield and kernel weight, and a reduction in screenings in terminal water deficit environments.

Tiller (botany)

Drought Tolerance

Anthesis

Water Stress

10.1093/jxb/ert181

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Citations (53)

Facets of the maximum crop yield problem

Field Crops Research (2015)

J. E. SHEEHY Lucas Borrás G. J. Rebetzke Víctor O. Sadras

Cold stress

WRKY protein domain

Transcription

10.1016/j.fcr.2015.08.011

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Citations (3)

Euphytica (2001)

G. J. Rebetzke Anthony G. Condon Richard A. Richards John J. Read

Stomatal Conductance

Transgressive segregation

10.1023/a:1012035720423

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Citations (31)

Variation in Adult Plant Phenotypes and Partitioning among Seed and Stem-Borne Roots across Brachypodium distachyon Accessions to Exploit in Breeding Cereals for Well-Watered and Drought Environments

PLANT PHYSIOLOGY (2015)

Vincent Chochois John P. Vogel G. J. Rebetzke Michelle Watt

Seedling roots enable plant establishment. Their small phenotypes are measured routinely. Adult root systems are relevant to yield and efficiency, but phenotyping is challenging. Root length exceeds the volume of most pots. Field studies measure partial adult root systems through coring or use seedling roots as adult surrogates. Here, we phenotyped 79 diverse lines of the small grass model Brachypodium distachyon to adults in 50-cm-long tubes of soil with irrigation; a subset of 16 lines was droughted. Variation was large (total biomass, ×8; total root length [TRL], ×10; and root mass ratio, ×6), repeatable, and attributable to genetic factors (heritabilities ranged from approximately 50% for root growth to 82% for partitioning phenotypes). Lines were dissected into seed-borne tissues (stem and primary seminal axile roots) and stem-borne tissues (tillers and coleoptile and leaf node axile roots) plus branch roots. All lines developed one seminal root that varied, with branch roots, from 31% to 90% of TRL in the well-watered condition. With drought, 100% of TRL was seminal, regardless of line because nodal roots were almost always inhibited in drying topsoil. Irrigation stimulated nodal roots depending on genotype. Shoot size and tillers correlated positively with roots with irrigation, but partitioning depended on genotype and was plastic with drought. Adult root systems of B. distachyon have genetic variation to exploit to increase cereal yields through genes associated with partitioning among roots and their responsiveness to irrigation. Whole-plant phenotypes could enhance gain for droughted environments because root and shoot traits are coselected.

Brachypodium distachyon

Root system

Tiller (botany)

Drought Tolerance

Brachypodium

10.1104/pp.15.00095

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Citations (44)

Inheritance of coleoptile tiller appearance and size in wheat

Australian Journal of Agricultural Research (2008)

G. J. Rebetzke Cándido López-Castañeda Tina Acuña Anthony G. Condon Richard A. Richards

Selection for rapid leaf area growth has the potential to increase wheat biomass, and both water-use efficiency and weed competitiveness early in the season. Several morphological components contribute to increased seedling leaf area, including rapid seedling emergence and production of longer, wider leaves. Early emergence of a large coleoptile tiller has also been demonstrated to increase plant leaf area and biomass in wheat and other grass seedlings. Yet little is known of the extent and nature of genotypic variation for coleoptile tiller growth in wheat. A random set of 35 wheat, barley, and triticale genotypes was evaluated in glasshouse and outdoor studies for seedling characteristics, including coleoptile tiller growth and total plant leaf area. Coleoptile tillers were produced more reliably for seedlings grown outdoors and when supplied with additional soil nitrogen. Genotypic differences in coleoptile tiller frequency and leaf area were large, ranging from 0 to 78% and from 0.0 to 1.4 cm2, respectively at very early growth stages. Australian commercial wheats tended to produce fewer coleoptile tillers of smaller size than overseas germplasm where the coleoptile tiller accounted for up to 12% of total seedling leaf area. This compared favourably with mainstem tiller leaf area, which ranged from 0 to 3.5 cm2 and accounted for up to 16% of plant leaf area. Broad-sense heritabilities were high for coleoptile tiller presence and size in favourable conditions (c. 75%) but low (c. 40%) for seedlings evaluated across nitrogen content-varying soils. Generation means analysis was used to investigate genetic control for coleoptile tiller growth across multiple populations. Significant (P < 0.05) differences were observed among generations for coleoptile tiller frequency and growth (numbers of leaves, leaf area, and biomass). These differences reflected strong additive genetic control with little evidence for any gene action × year interaction. Increases in coleoptile tiller frequency and mass were correlated with larger embryo size and wider seedling leaves to increase seedling leaf area (rg = 0.89). Comparisons between reciprocal F1 and F2 generation means indicated strong maternal effects for coleoptile tiller growth in some but not all crosses. Screening in favourable environments will increase heritability and aid in selection for progenies producing large coleoptile tillers. Evidence for additive genetic control should permit early generation selection but not without some progeny-testing for coleoptile tiller growth together with other early vigour components associated with increased plant leaf area.

Coleoptile

Tiller (botany)

10.1071/ar07397

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Citations (31)

Prospects for yield improvement in the Australian wheat industry: a perspective

Food and Energy Security (2016)

M. J. Robertson John A. Kirkegaard G. J. Rebetzke Rick Llewellyn Tim Wark

Abstract For the Australian grains industry, recent progress in wheat yield (the dominant crop) due to genetic improvement and advances in agronomy is assessed, and we propose some of the emerging technologies that are likely to contribute to yield gain in the medium (10–20 years) term. Advances in yield will be underpinned by new genetics tailored to agronomic technologies with progress in water‐limited yield potential expected to increase from current levels of ca. 0.5% per year. This increase will be achieved by selecting traits with greater water productivity, tolerance to frost and high temperature, and resistance to a range of soil constraints through access to novel genetic diversity, and deployment of targeted biotechnology and tools to improve confidence in phenotyping and environmental characterization. Hybrid cereals should halve the time to cultivar delivery to less than 6 years while allowing for more rapid incorporation and delivery of new traits, and capacity to exploit heterosis. There will be better adoption of recent technologies (such as variable‐rate technology, soil testing, soil amelioration, and timely sowing) with the potential to increase yield by 10–80%. Novel technology packages such as earlier sowing systems will be enabled by improvements in integrated weed management, seasonal climate forecasting, plastic mulches, materials science, information and communication technologies, and weather monitoring and soil sensing. With a conservative assumption about maintaining the current rate of genetic progress at 0.5% per year, ongoing adoption of current and new agronomic technologies, continuing investment in R&D, and farm consolidation, at a whole industry level, annual gains in wheat yields of around 20 kg/ha (0.8–1.0%) are feasible over the next 20 years. These gains are likely to be attenuated by only a modest impact (<10% reduction) on crop yield potential due to the negative impacts of climate change.

Emerging Technologies

Genetic gain

10.1002/fes3.81

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Citations (31)