Heat impact on yield components of fertile primary tillers in wheat can inform crop modelling for future climates

Karine Chenu, Florianne Oudin

The University of Queensland, Queensland Alliance for Agriculture and Food Innovation (QAAFI), Toowoomba, QLD, Australia
Email: karine.chenu@uq.edu.au


In recent decades, rising temperatures have increasingly affected wheat crops in major producing regions around the world. Climate models predict further increases in mean temperature and in the frequency of temperature extremes for the near to mid-future.

The impact of heat on wheat at different periods of the crop cycle was studied in two experiments conducted with finely controlled temperatures in a glasshouse. While heat shocks affected the main stem and primary tillers of a plant differently, a common response to heat was found for all stems (irrespective of their rank), when considering the timing of the stress relative to stem anthesis. The greatest impact on grain number was observed for stress applied ~10 days before stem anthesis. The impact of pre-anthesis stress on grain set were slightly compensated by an increase in individual grain weight. Overall, grain yield was substantially affected for early pre-flowering stress and early-to-mid post-flowering stress. The results of this study have been used to improve estimations of heat impact in crop modelling and thus improve the accuracy of crop simulations for future climate scenarios.

Canola yield and its association with phenological, architectural and physiological traits across the rainfall zones of southwestern Australia

Heping Zhang, Jens Berger, Chris Herrmann, Adam Brown, Sam Flottmann

CSIRO Agriculture and Food, Private Bag 5, Wembley, WA6014


Canola yield is a complex trait determined by environmental and genetic factors, and their interaction. We investigated yield performance of 21 canola across multiple environments and its association with flowering time, architectural and physiological traits. Pattern analyses showed that environment discriminated varieties differently, from which two mega-environments and four variety groups were identified. Principal component analysis (PCA) revealed specific adaptation: i.e. yield was associated with early flowering in the low/medium rainfall zone (LMRZ) and with late flowering in the high rainfall zone (HRZ). A few varieties outperformed all other varieties across environments and were broadly-adapted. PCA revealed that yield was positively associated with biomass and HI but negatively with days to flowering in the LMRZ, and positively with biomass, longer days to flowering and more seeds m-2 but negatively with HI in the HRZ. The combination of high harvest index and biomass of broadly-adapted varieties enabled them to produce high yield across the environments.

Linking wheat grain quality to environmental processes

Garry O’Leary1, Cassandra Walker1, Joe Panozzo1, Thabo Thayalakumaran2, Malcolm McCaskill3, James Nuttall1, Kirsten Barlow4, Brendan Christy4 and Senthold Asseng5

1 Agriculture Victoria, 110 Natimuk Road, Horsham, VIC 3400 garry.oleary@ecodev.vic.gov.au gjoleary@yahoo.com, 
2 AgriBio, 5 Ring Road, Bundoora, VIC 3083,
3 Agriculture Victoria, 915 Mount Napier Road, Hamilton, VIC 3300,
4 Agriculture Victoria, 124 Chiltern Valley Road, Rutherglen, VIC 3685 Australia Present address: Precision Agriculture, 113 High Street Rutherglen, VIC 3685,
5 University of Florida, Gainesville, FL 32611-0570, USA


Maintaining high quality grain from Australian dryland production systems is under threat from three main environmental factors.  These are rising atmospheric CO2 concentrations, increasing frequency of drought and higher temperatures both as average increase and more frequent heat waves.   For wheat, we propose a new hypothesis and simulation model for predicting the environmental effects on the synthesis of glutenin and gliadin proteins, two important quality parameters which control end-use properties.  This model is applicable for the diverse environments encountered in Australia and France.  Mechanistically linking changes in composition of these rheologically-important proteins to environmental conditions should support targeted breeding selection of suitable genes to help maintain grain quality in wheat and provide a marketing edge for Australian grain.

Impact of post-flowering heat stress on stay-green and grain development in wheat

Najeeb Ullah1, Karine Chenu1

1 The University of Queensland, Queensland Alliance for Agriculture and Food Innovation (QAAFI), Toowoomba, QLD, Australia Email: n.ullah@uq.edu.au;  karine.chenu@uq.edu.au


With recent and projected changes in climate, wheat crops are increasingly likely to experience post-flowering heat stress. An experiment was conducted to assess the impact of post-flowering heat on wheat crop. Recombinant inbred lines SB062 and SB003 were exposed to a 7-day heat shock (32.7/21.6°C day/night temperature) at different periods during the grain filling. These post-flowering heat shocks accelerated leaf senescence, with a greater impact on older leaves and for mid post-flowering stresses. Substantial genotypic differences were observed, with SB062 maintaining leaf greenness longer than SB003 especially when submitted to a heat stress. High temperature also reduced grain dimension and weight, especially for stresses applied during early-to-mid grain filling. SB062 was found as heat tolerant, as neither senescence of its two top leaves nor its grain size were significantly affected by heat in the tested conditions. Delayed leaf senescence appeared to play a role in maintaining grain size in SB062 under heat stress. The research findings will assist improving crop models for post-flowering heat effects and developing techniques for screening heat tolerant wheat lines.

Sample size is critical when exploring the grain set in wheat cultivars grown under frost-prone field conditions in Western Australia

Brenton Leske1, Ben Biddulph2, Mario D’Antuono2, Ifeyinwa Olive Onyemaobi2 and Timothy Colmer

1 University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, brenton.leske@research.uwa.edu.au2 Department of Primary Industries and Regional Development, 3 Baron-Hay Court, South Perth, WA 6151


Quantifying the grain set and floret sterility (FS) of wheat cultivars is crucial to benchmarking their susceptibility to frost and exploring cultivar differences so that genetic improvement can be made. Ensuring that the measurement of grain set and FS is accurate and adequately captures the variation within and between spikes and cultivars, is vital to making progress in this space. A field trial with eight times of sowing blocks (from mid-April to early-June) was established at Dale, Western Australia to evaluate the susceptibility to frost of 15 wheat cultivars, of which three are reported on in this paper. Variance component analysis was used to determine the optimal sample size from a sub-set of three wheat cultivars with known differences in their susceptibility to frost damage (Impose CL Plus, Kunjin and Magenta). The optimal sample size was determined to be 15 to 20 spikes per plot, when grain positions per spike ranged from 25 to 35.. Future phenotyping experiments exploring stresses or traits related to spike fertility would benefit from undertaking a variance component analysis to ensure efficient use of their resources.


Can 15N- isotopic methods be used to estimate plant associated nitrogen fixation in hybrid perennial sorghum?

Matthew T. Newell1, Timothy E. Crews2 and Richard C. Hayes3

1 NSW Department of Primary Industries, Cowra Research and Advisory Station, Binni Creek Rd, Cowra, NSW 2795 matt.newell@dpi.nsw.gov.au,
2 The Land Institute, 2440 E. Water Well Rd., Salina, KS 67401, United States of America,
3 NSW Department of Primary Industries, Wagga Wagga Agricultural Institute, PMB, Wagga Wagga, NSW 2650


A redesign of current cropping systems that incorporates grain production from perennial species has been proposed as a method of sustainable staple grain production. Perennial sorghum is one such species under development as a grain crop, which has been suspected of hosting endophytic nitrogen fixing bacteria in its stems or crowns. A pilot study using isotope dilution methodology was used to measure the percent nitrogen derived from the atmosphere (%Ndfa) in perennial sorghum. Plants were grown in three metre columns over 90 days set in the field. Three treatments providing high (HN), low (LN) and zero (0N) N applied as urea were compared, with each treatment consisting of a perennial sorghum plant grown in the same column with Lolium rigidum and L.perenne. Additional nitrogen from urea significantly (P< 0.05) increased total shoot and root dry matter, compared to the 0N treatment. Interestingly, perennial sorghum plants in the 0N treatment had significantly (P< 0.05) longer roots and a higher root:shoot ratio (P< 0.05) compared to both additional N treatments. This suggests that N scarcity stimulated increased root allocation. Perennial sorghum showed no evidence of N2 fixation under the HN and LN treatments at all sampling dates. However, over time in the 0N treatment there was a trend for increasing levels of biologically sourced N with an average of 30 %Ndfa at the final sampling date, although calculations varied with the reference species used. The current study provides evidence of N2 fixation in perennial sorghum but highlights concerns about the adequacy of the reference plant δ15N values.

Chickpea yield potential in cool conditions – making the most of early flowers

Neroli Graham1, Annie Warren2, Rosy Raman3 and Kristy Hobson1

NSW DPI, 4 Marsden Park Road Calala NSW 2340, neroli.graham@dpi.nsw.gov.au,
2 NSW DPI, 4 Marsden Park Road Calala NSW 2340,
3 NSW DPI, Pine Gully Road Wagga Wagga NSW 2650


The sensitivity of current Australian chickpea cultivars to cool temperatures during flowering and podset results in delayed and interrupted podset. In 2016 in north-western NSW, this sensitivity resulted in an estimated yield loss of 0.5 to 0.7 t/ha based on observationsin commercial paddocks. This project aimed to improve our knowledge of the response of current genotypes to cool temperatures and identify elite chickpea breeding lines with superior chilling tolerance. Twenty-four genotypes were sown at Tamworth and Wagga Wagga in early May and June to encourage flowering under suboptimal temperatures. Comparative phenology was tracked among the lines throughout the season and conversion of flowers to pods and seeds mapped on individual plants. Genetic variation in the ability of genotypes to flower and set pods under suboptimal temperatures were identified.Identification of chilling tolerance in elite breeding material will inform breeding efforts, , potentially improving the ability of future cultivars to set pods under sub optimal temperatures,  enabling shifts in the cropping window to avoid terminal heat and moisture stress.

Evaluating wheat, barley and oat for early sowing under frost-prone field conditions in Southern Australia

Ariel Ferrante1, Ben Biddulph2, Jason A. Able1

1 School of Agriculture, Food and Wine. The University of Adelaide, Adelaide, Australia, ariel.ferrante@adelaide.edu.au,
2 Department of Agriculture and Food, Western Australia, South Perth, Australia


Low temperatures during the flowering period of cereals can lead to floret sterility and yield reduction, resulting in economic losses in Australian crops. In this study, we investigated the relative suitability of wheat, barley and oat in a frost-prone landscape. In addition, we analysed across the sowing program the most stable and profitable cereal (i.e. gross margin). We tested the hypothesis that wheat was as profitable as barley and oat when phenology matched the optimum time of sowing.

Yield and yield components, and floret sterility were measured, while gross margins were calculated. The factorial experiment combined six wheat, three barley and three oat varieties under three sowing dates (19th April, 4th May, and 22nd May 2017).

Results suggested that long-maturity varieties were best suited to an early sowing time (mid-April). Kittyhawk (wheat), Urambie (barley) and Banister (oat) avoided frost damage during the critical period around anthesis. Later sowing was best suited to short-maturity types such as La Trobe (barley) and Cutlass (wheat). Oat was not economically viable in the frost-prone trial region, returning a negative gross margin across all sowing times. While heat and drought stress were not quantified in this study, these abiotic stress constraints play a crucial role during the grain filling stage; and as such can have a profound effect on the final number of grain number m-2 and therefore grain yield.

Assessing frost damage in a set of historic wheat varieties using a passive heating system

Ariel Ferrante1, Cesar M. Cossani1, 2, Jason A. Able1, Victor O. Sadras1, 2

1 School of Agriculture, Food and Wine. The University of Adelaide, Adelaide, Australia, ariel.ferrante@adelaide.edu.au,
2 South Australian Research and Development Institute, Adelaide, Australia


Low temperatures during the flowering period of cereals can lead to floret sterility, yield reduction, and economic losses in Australian crops. In this study we investigated the physiological bases of yield determination in a historic set of wheat varieties grown under frost-prone field conditions in Southern Australia. We tested the hypothesis that selection for yield inadvertently improved frost tolerance. We measured yield and yield components, including the distribution of grains within the spike, in a factorial experiment combining twelve wheat varieties (released from 1973 to 2015), two sowing dates (19th April and 22nd May 2017), and two thermal regimes, ambient control and frost-protected. To protect crops from frost we used moveable, lightweight passive heating systems before each frost event (≤ 0°C). Phenotypic plasticity of yield, grain number and grain weight were analysed. We found a positive relationship between phenotypic plasticity of grain yield and phenotypic plasticity of grain number, but no correlation between yield and year of release. Across varieties, the average numbers of grains per spike was 35.1 ± 0.3 in frost-protected crops compared to 16.1±0.1 in frosted controls in the first sowing, and 29.7 ± 0.3 and 22.9 ± 0.2 respectively in the second sowing. Preventing frost improved spike fertility by increasing the proportion of grains in distal positions within spikelets in relation to controls.

Dynamics of Evaporation and Transpiration in Overhead Sprinkler Irrigation

Jasim Uddin1

1 Trangie Agricultural Research Centre, NSW Department of Primary Industries, Mitchell Highway,  Trangie, NSW, 2830



Evaporation and transpiration are the central components of the water balance in irrigated and rain-fed cropping systems. Their dynamics and the energy budget at pre, during- and post-overhead sprinkler are unique from other irrigation methods such as surface and drip. The photosynthesis process and net exchange of carbon dioxide (CO2) are also different in wet canopy conditions compared with dry canopy conditions. However, these phenomena are not well understood in water and energy budget during the different phases of overhead irrigation events. A study was conducted in a cotton field using eddy covariance and sap flow systems to observe the dynamics of evaporation, transpiration, energy fluxes and exchange of (CO2) in different phases of overhead irrigation. Data showed a marked increase in evapotranspiration rate during   irrigation, a consequence of the high evaporation rate of water intercepted by the canopy. Canopy development has a distinct effect on evaporation rates. Evapotranspiration rates declined after irrigation as the canopy dried. Transpiration rates considerably reduced during irrigation but quickly recovered in the post-irrigation phase. The exchange of CO2 decreased substantially during irrigation, possible due to a reduction in photosynthesis and closure of stomatal openings under wet canopy conditions. The energy fluxes show that sensible and latent heat act in opposite ways. Both may contribute to the evaporation of canopy intercepted water.



The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

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