SYSTEMS ANALYSIS OF SHADE-AVOIDANCE RESPONSES AS A MECHANISM OF CROP YIELD LOSS DUE TO WEEDS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: TERMINATED
• Funding Source: AFRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 1009010
• Grant No.: 2016-67013-24912
• Project No.: WYO-569-16
• Proposal No.: 2015-06767
• Program Code: A1131
• Project Start Date: Feb 1, 2016
• Project End Date: Jan 31, 2021
• Grant Year: 2016

Project Director
Kniss, A.

Recipient Organization
UNIVERSITY OF WYOMING
1000 E UNIVERSITY AVE DEPARTMENT 3434
LARAMIE,WY 82071-2000

Performing Department
Plant Sciences

Non Technical Summary
It is well known that weeds reduce crop yield, but our understanding of the underlying mechanisms that cause yield loss is incomplete. Resource depletion is undoubtedly a major contributor to crop yield loss; as weeds use water, nutrients, and light, there is less available for the crop. But other mechanisms also contribute to yield loss due to weeds, including phytochrome-mediated changes in growth collectively called shade avoidance responses. Preliminary studies suggest shade avoidance can reduce Beta vulgaris yield up to 70%, even without direct competition for resources. This could lead to a fundamental shift in the current weed management paradigm, since no amount of added resources (like irrigation or fertilizer) could reverse the impact of shade avoidance responses caused by early season weeds. The long-term goal of this project is to reduce the impact of weeds through greater understanding of the ecological processes that drive crop yield loss due to weeds. Using large-pot experiments under field conditions, we will (1) determine the growth stages during its life cycle that Beta vulgaris yield is affected by shade avoidance responses; (2) quantify the root to shoot ratio changes from shade-avoidance responses and subsequent impact on soil water use and competition between weeds and Beta vulgaris; and (3) use a process model-data fusion approach to test and improve predictions of crop yield loss from weed competition. This work will improve our ability to predict and mitigate yield loss due to weeds under a range of environmental conditions.

Animal Health Component

0%

Research Effort Categories

Basic

30%

Applied

70%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
213	2010	1070	100%

Knowledge Area
213 - Weeds Affecting Plants;

Subject Of Investigation
2010 - Sugar beet;

Field Of Science
1070 - Ecology;

Keywords

beta vulgaris

competition

crop production

shade avoidance

sugarbeet

weed control

Goals / Objectives
The long-term goal of this project is to improve the sustainability of crop production through predictive understanding of the mechanism of crop yield loss due to weeds. In order to accomplish our long-term goal, we propose the following specific objectives for this research project:Determine the growth stages during its life cycle that Beta vulgaris yield is affected by shade avoidance responses.Quantify the root to shoot ratio changes from shade-avoidance responses and subsequent impact on soil water use and competition between weeds and Beta vulgaris.Use a process model-data fusion approach to test and improve methods for predicting crop yield loss from weed competition.

Project Methods
The proposed research will use a similar pot design successfully employed in preliminary studies. These methods are adapted from those described by Green-Tracewicz et al. (2011), and we have been adjusting and improving the methods over the last 3 years. Ulrich (1961) concluded that when using individual sugarbeet plants as experimental units, a minimum of 11 replicates should be used to ensure statistical power to detect treatment differences, but breeding has greatly improved uniformity of Beta vulgaris germplasm since that time. Sub-sampling of preliminary data indicates that statistical differences between treatments could be detected consistently with as few as 5 replicates per treatment. We propose using 8 to 10 replicates of each treatment by cultivar combination for each destructive sample required, to ensure adequate statistical power earlier in the season when effect sizes may be smaller than at the end of the season. Sugarbeet and Swiss chard will be used for all studies.For Objective 1, we will impose weedy treatments using alarge-pot design from the time of planting, then remove the weedy environment and replace with soil at different times during the season. For Objective 2,we will test the hypothesis that shade avoidance may cause crop yield loss similar to or even greater than direct competition for water. To test this hypothesis, we will establish a factorial arrangement of five crop-weed interaction treatments and three irrigation levels.Crop-weed interaction treatments:Full below-ground competition with shade avoidance. In this treatment, the bucket design described above will be used, but without the plastic barrier to separate grass roots.Full below-ground competition without shade avoidance. This treatment will be similar to treatment 1, but the cardboard tube will be allowed to extend 2 cm above the soil. The tube will provide a barrier between the Beta vulgaris plant and the grass ring to prevent reflected far-red light from reaching the Beta vulgaris plant.No competition control for treatment 2. It is possible that simply increasing the height of the cardboard tube in treatment 2 will have a negative impact on Beta vulgaris growth due to shading. This treatment will be included as a control treatment to quantify this shading effect. The treatment will be the same as treatment 2, except no grass will be planted in the surrounding ring.Shade avoidance only. This treatment will be the same as for the season long shade avoidance pilot study. Beta vulgaris will be exposed to the weedy light environment, but roots will not be allowed to interact.No competition. This will serve as a control treatment, where no grass will be planted, and the cardboard tube will be at a similar height as treatments 1, 2, and 4.Irrigation treatments:100% evapotranspiration80% evapotranspiration60% evapotranspirationFor Objective 3,we will make probabilistic statements (e.g., Figure 7) on plant competition through inverse ecophysiological modeling (outlined below) using elements of scaling theories and ecophysiological mechanisms within the plant growth routines in TREES (Terrestrial Regional Ecosystem Exchange Simulator) (Samanta et al., 2007; Loranty et al., 2010; Mackay et al., 2012; McDowell et al., 2013).TREES is an ecophysiological model of plants or competing cohorts of plants coupled with the soil and atmospheric environments, within a Bayesian statistical framework. The model represents a continuum from soil to atmosphere via plant rhizosphere, absorbing roots, conducting roots, conducting shoots, and lateral shoots or canopies. The continuum is modeled using physical equations of water flow and dissolved nutrients under negative pressure from soil to atmosphere.Data collection, analysis, and interpretationFor all studies, non-destructive measurements collected at 7 day intervals throughout the season will include leaf counts, leaf lengths, petiole lengths, and leaf angles. These response variables have been influenced by shade avoidance treatments in pilot studies. Additional data will be collected at four destructive harvests throughout the season at approximately 20 d intervals from Beta vulgaris emergence. Harvest measurements (destructive sampling) will include total leaf area (using a Delta T leaf area meter available in the Kniss laboratory), leaf length and petiole length for each leaf; total leaf biomass (dry weight); root fresh weight, diameter, and length (sugarbeet only); and total root biomass (dry weight). After measuring and weighing, sugarbeet roots will be chopped using a food processor, split into two sub-samples, vacuum sealed, and immediately frozen. One of each frozen subsample will be delivered to the Western Sugar tare lab for sucrose quality analysis. The other sub-sample will be used to quantify total non-structural carbohydrates and starch for allocation mechanisms. Non-structural carbohydrates and starch will also be collected from Swiss chard samples. Recent research by McKenzie-Gopsill et al. (2015) has suggested that shade avoidance cues impact carbon assimilation, altering sugar and starch conversion.

Progress 02/01/16 to 01/31/21

Outputs
Target Audience:Crop and weed scientists, plant physiologists, sugarbeet growers, weed & pest district supervisors, and extension specialists. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Three doctoral students and two postdoctoral research associates were actively involved in the project, and were trained on various aspects of plant physiology, crop production, weed management, statistical analysis and mechanistic modeling. Several undergraduate students were also actively involved in data collection. How have the results been disseminated to communities of interest?Results have been presented to scientists at multiple meetings (Weed Science Society of America, American Society of Sugar Beet Technologists, among others). One journal article has been published and three more journal articles are in some stage of preparation. We have presented results to sugarbeet growers in the western region and multiple field days and winter extension meetings, and will write additional articles to continue to reach out to this audience. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? The period between sugarbeet emergence and the two true-leaf stage was found to be extremely important with respect to weed impacts on yield potential. If weeds were present from emergence until the two true-leaf sugar beet stage, sugar beet leaf area was reduced 22%, leaf biomass reduced 25%, and root biomass reduced 32% compared to sugar beet grown season-long without surrounding weeds. Leaf area, leaf biomass, and root biomass was similar whether weeds were removed at the two true-leaf stage (approximately 330 GDD after planting) or allowed to remain until sugar beet harvest (approximately 1240 GDD after planting). Adding weeds at the two true-leaf stage and leaving them until harvest (~1240 GDD) reduced sugar beet leaf and root biomass by 18 and 23%, respectively. Under fully irrigated conditions, shade avoidance reduced leaf number 15% (P=0.001) but did not significantly reduce leaf area (P=0.85) compared to the no competition treatment. Under severe drought stress, similar effects were observed on leaf number (15% reduction, P=0.002) and leaf area (P=0.96). Root biomass production was reduced 19% by shade avoidance under fully irrigated conditions (P=0.03), but shade avoidance did not reduce root biomass production under severe drought stress compared to no competition (P=0.99).In contrast to many plants, sugar beets produce smaller and shorter plants under shade avoidance signals (low R:FR light). Sugarbeets were able to maintain biomass under severe water stress while undergoing shade avoidance. We developed hierarchical Bayesian predictive models that 1) partition the variance and uncertainty among the plant and environmental measurements and the hypothesized growth components, and 2) validated the negative effects of non-root competition on below ground biomass early in growth but not late in growth. These models showed a high probability that belowground sugar beet biomass is primarily related to leaf growth. Thus future work should be focused on better measurements and models of leaf growth. We also tested a biophysical model (TREES) using meteorological data (temperature, relative humidity, windspeed, photosynthetically active radiation) from the sugar beet study site to simulate growth of sugar beets. The biophysical parameters (parameters that show how mass, and energy are conserved and flow based on physical properties of the plant) used in this model are from a different crop species (Brassica rapa) however, the growth trajectories and patterns were comparable to what was observed in sugar beets. We are now testing which biophysical parameters need to be changed to parsimoniously simulate sugar beet growth and productivity.

Publications

Progress 02/01/18 to 01/31/19

Outputs
Target Audience:Presentations were given to sugarbeet growers, crop consultants, and scientists. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?A PhD student, PostDoc, and several graduate and undergraduate students have workded directly on this project. In addition, the data has been used in coursework from which over 30 undergraduate students have benefitted. How have the results been disseminated to communities of interest?1 peer-reviewed journal article and several presentations have been given. The results have also been dissemenated on social media channels from time to time. What do you plan to do during the next reporting period to accomplish the goals?Continue with the water by shade interaction study, continue with TREES modeling, and finalize the duration study.

Impacts
What was accomplished under these goals? A large-pail field study included a range of weed addition and removal timings to quantify sugarbeet growth parameters and yield. The model weed, Kentucky bluegrass (Poa pratensis) was grown in a separate container from sugarbeet so there was no root interaction, and the grass was clipped regularly to prevent direct shading of the sugarbeet plants. Season-long weed presence from sugarbeet emergence to harvest reduced most sugarbeet growth parameters, including leaf number, leaf area, and biomass production. If weeds were present beginning at sugarbeet emergence but removed at the sugarbeet 2 true-leaf stage, most sugarbeet growth and yield measurements were similar to the season-long weedy treatment. For example, compared to the weed-free control treatment, season-long weed presence reduced sugarbeet root fresh weight by 32%, while removing weeds at the 2 true-leaf stage reduced sugarbeet root fresh weight by 33%. Similarly, sugarbeet leaf area was reduced 27% by both the season-long weedy treatment and 2 true-leaf removal treatment. It appears that if sugarbeet is exposed to shade avoidance signals during emergence, substantial yield potential can be lost even if weeds are removed by the 2 true-leaf stage.

Publications

• Type: Journal Articles Status: Published Year Published: 2019 Citation: Schambow TJ, Adjesiwor AT, Lorent L, Kniss AR (2019) Shade avoidance cues reduce Beta vulgaris growth. Weed Sci. 67:311317. doi: 10.1017/wsc.2019.2

Progress 02/01/17 to 01/31/18

Outputs
Target Audience:We have presented information from this study to both farmers and other scientists. Changes/Problems:We experienced problems with high-winds affecting the timing study in 2017, so we plan to repeat that study in 2018. What opportunities for training and professional development has the project provided?Two graduate students and one undergraduate student have been heavily involved in this project. How have the results been disseminated to communities of interest?Presentations at grower meetings and scientific presentations have been made. What do you plan to do during the next reporting period to accomplish the goals?We will continue as planned conducting the field work, and the modeling will begin during the next several months.

Impacts
What was accomplished under these goals? We evaluated effects of reflected far red light from grass (Kentucky bluegrass) on growth and non-structural carbohydrate (NSC) partitioning of sugarbeet. The grass treatment significantly increased cotyledon length (2.2 vs 1.5 cm) and width (0.6 vs 0.5 cm) in 2016, and cotyledon length to width ratio in 2016 (3.8 vs 2.8) and 2017 (4.7 vs 4.3). The grass significantly reduced number of leaves such that there were three less leaves in the grass treatment at final harvest in both years. The grass treatment significantly reduced leaf area, shoot dry weight root diameter, and root dry weight in 2016. Generally, weed treatments did not significantly affect root and shoot NSC concentrations. Root soluble CHO increased with increasing DAP and ranged from 77 to 653 mg g-1 while root starch decreased with increasing DAP and ranged from 34 to 88 mg g-1. Same trends were observed in shoot NSC. Shoot soluble CHO ranged from 52 mg g-1 to 197 mg g-1 while starch ranged from 39 mg g-1 at 50 DAP to 164 mg g-1. Thus, NSC allocation in sugarbeet is maintained even under perceived competition. Therefore, the opportunity cost for optimal NSC allocation is reduced growth.

Publications

• Type: Conference Papers and Presentations Status: Accepted Year Published: 2017 Citation: Adjesiwor AT, Kniss A (2017) Response of Beta vulgaris to reflected light quality. Proc Weed Sci Soc Am.

Progress 02/01/16 to 01/31/17

Outputs
Target Audience:Scientists working in crops and weeds, as well as farmers growing sugarbeet and other crops. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Multiple graduate students and undergraduate students have been exposed to this work, and the data has formed the basis of several class discussions about shade avoidance and mechanisms of crop yield loss due to pests. How have the results been disseminated to communities of interest?Results have been presented to farmers at meetings and field days, scientists and ag practitioners at professional society meetings, and undergraduate students in coursework. What do you plan to do during the next reporting period to accomplish the goals?Continue with the timing and resource partitioning studies as planned in the proposal.

Impacts
What was accomplished under these goals? B. vulgaris was sampled at 90 days after planting (DAP) in 2014, and 56 and 73 DAP in 2015. In two (56 and 73 DAP in 2015) out of three studies, B. vulgaris root starch and soluble CHO were similar between grass and control treatments. When harvested at 90 DAP in 2014, the ratio of root starch to soluble CHO was higher in B. vulgaris exposed to the grass treatment compared to soil control treatment (P=0.02). These results provide some evidence that shade avoidance may affect the proportion of CHO stored as soluble sugars and starch in roots of B. vulgaris. The grass treatment modified B. vulgaris petiole to leaf length ratio and significantly reduced number of leaves, leaf area, root fresh weight, and top fresh weight. B. vulgaris produced, on average, 4 fewer leaves in the grass treatment compared to the control (no grass) at harvest (73 days after planting). Similarly, the grass treatment reduced top fresh weight, leaf area and root fresh weight by 27, 27, and 21% respectively.

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Adjesiwor AT, Schambow TJ, Kniss AR. 2016. Effects of shade avoidance on growth and yield of Beta vulgaris. Proc. Weed Sci. Soc. Am. 2016:365.
• Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Adjesiwor AT, Schambow TJ, Kniss AR. 2016. Role of shade avoidance in critical period of weed control in Beta vulgaris. Proc. Weed Sci. Soc. Am. 2016:82.
• Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Adjesiwor AT, Schambow TJ, Kniss AR. 2016. Response of Light-Grown Beta vulgaris to Reflected Far-red Light. Proc. Western Soc. Weed Sci. 69:141.
• Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Adjesiwor AT, Schambow TJ, Kniss AR. 2016. Physiological mechanisms of shade avoidance response in Beta vulgaris. Proc. Western Soc. Weed Sci. 69:060.