Location: Sunflower and Plant Biology Research
2016 Annual Report
Objectives
Objective 1: Identify, at the genome and physiological levels, plant-plant interactions that impact plant growth and lead to crop yield losses, especially crop-weed interactions that occur during the critical weed-free period, and interactions that occur between the different crops inter-planted in relay cropping systems, such as corn, soybeans, or sunflowers relayed with camelina, ryegrass, or canola. [NP304, Component 2, Problem Statement 2A3]
Sub-objective 1.A: Determine the parameters for evaluating the impacts of winter annual cover crops on corn, sunflower, and Amaranthus spp. productivity.
Sub-objective 1.B: Identify physiological and molecular mechanisms that control interactions between cover crops and corn, sunflower, and Amaranthus spp.
Sub-objective 1.C: Evaluate impacts of candidate genes on cover crop-relay crop and cover crop-weed interactions.
Objective 2: Determine the molecular and physiological mechanisms by which winter annual cover crops suppress weeds in northern temperate agroecosystems, and identify genes that will enhance weed suppression in these crops, such as genes associated with weed-tolerance, cover-crop tolerance, and cold hardiness. [NP304, Component 2, Problem Statement 2A3]
Sub-objective 2.A: Identify genetic markers for improving the weed-suppressing trait of winter hardiness in winter canola and/or camelina varieties.
Sub-objective 2.B: Evaluate the weed-suppressing traits of winter-hardy canola and camelina in the field.
Approach
Weeds are major pests of agro-ecosystems that reduce production of the nation’s food, feed, fiber and fuel crops. The industry-adopted practice of rotating crops with engineered tolerance to a limited set of herbicides continues to put selection pressure on the evolution of herbicide-resistant weeds. As part of a holistic and sustainable approach to managing weeds in temperate agro-ecosystems, we propose to identify cover crop-relay crop interactions to enhance relay crop productivity, cover crop-weed interactions to enhance weed suppression, and identify winter-hardy annual cover crops that suppress weeds in relay cropping systems. In this proposal, winter canola will serve a dual purpose as both a cover crop for evaluating weed suppression, and as a surrogate weed for weed-relay crop interactions. Our model relay cropping system consists of inter-seeding a commodity crop (corn or sunflower) into an established cover crop (winter canola) such that their lifecycles overlap. Currently, no winter-hardy annual broadleaf cover crops are economically suited for weed suppression in relay cropping systems in the upper Midwest (UMW) and Northern Great Plains (NGP). Consequently, the objectives of this project are: (1) elucidating regulatory signals and pathways associated with cover crop-relay crop and cover crop-weed interactions that impact plant productivity, and (2) identifying economically suited winter-hardy broadleaf cover crops that suppress weed establishment in inter-seeded relay crops. These objectives will be accomplished through the use of physiological, molecular, and genomic approaches, with the long-term goals of revolutionizing weed management practices.
Progress Report
Progress on plant-plant interaction studies. In nature, plants compete for light, water, and nutrients. As a result, plants have evolved various mechanisms for recognizing their competitive neighbors, which often induces developmental programs that optimize seed biological success over yield. In the case of weed-crop or cover crop-relay crop competition, these developmental shifts result in crop yield losses, even when light, water, and nutrients are not limiting. To begin investigating this phenomena, preliminary plant-plant interaction studies have been conducted by ARS scientists at Fargo, ND. These preliminary studies revealed that 6 weeds induce adequate pressure for reliable yield reduction in sunflower grown in pots under greenhouse conditions. Both hybrid and inbred lines of sunflower responded similarly to this weed pressure. Interestingly, some variability in weed response of sunflower was attributed to maternal environmental conditions as well as genotype. However, it was also observed that a cover crop (i.e., winter canola) was far more competitive with sunflower than any of the three Amaranthus species tested (grain amaranth, glyphosate-resistant Palmer amaranth, and Amaranthus powelii), regardless of the sunflower variety tested or the intensity of the weed pressure. These studies helped to identify suitable stages of development for determining when weeds (or potential cover crops) have a measurable and significant impact on sunflower phenology. These preliminary studies further indicated that two genotypes of winter canola significantly suppresses growth and development of both Palmer amaranth and Amaranthus powelii under our greenhouse experimental protocol.
The first tests to determine the impact of Amaranthus powelii and Palmer amaranth, and two winter canola varieties, on two commercial corn hybrids have been completed. Although these preliminary results indicate that winter canola had the greatest impact on corn growth and biomass, the amaranth treated corn was not significantly different from the winter canola treated corn in any parameter measured at harvest.
Progress on screening winter canola and camelina for freezing tolerance. Cover crops provide ecosystem services and reduce establishment of spring and early summer weeds. Currently, few economically viable oilseed cover crops are tolerant to the harsh winter environments experienced in the upper mid-West and Northern Great Plains of the U.S. To identify potential winter-hardy oilseed cover crops, ARS scientists in Fargo, ND, in collaboration with a winter canola breeder from Kansas State University, are phenotyping and genotyping a winter canola diversity panel for freezing tolerance. Of the 413 accessions within our winter canola diversity panel, 396 accessions produced sufficient seed for future screening under greenhouse conditions. Fourteen of the winter canola accession had poor seed set, one did not germinate, and two did not flower, even after two vernalization treatments. The quality of DNA extracted from each accession used to bulk seed is being evaluated for future Genotyping-by-Sequencing, which is to be conducted under an agreement with Cornell University.
Development and fine-tuning of freezing tests and phenotyping protocols were conducted on a subset of 100 winter canola accessions and a winter and spring camelina accession. Greenhouse-grown winter canola and camelina plants were vernalized for 2 months prior to being subjected to a linear ramp-down in temperature from 4°C to -15°C or -17°C for 8 h, an extended 4 hour freezing treatment at -15°C or -17°C, followed by a linear ramp-up in temperature to 4°C over 8 h under. Subsequently, the plants were transferred to a greenhouse under ambient conditions for leaf damage ratings. Damage ratings indicated that freeze protocols done at -15°C or -17°C resulted in between 26% to 69%, or 13% to 23%, respectively, survival for winter canola. Based on the visual ratings, two of the winter accessions (ARS-203 & 206) have shown the most consistent survival from these studies. For camelina, survival of the winter (Joelle) and spring (CO46) varieties was 100% and 0%, respectively.
Preliminary phenotyping studies have also determined that fluorometer readings (Fv/Fo), obtained with a hand-held Fluorometer, provide a rapid method for high throughput, non-destructive screening of winter canola following a freeze protocol. The results indicate that Fv/Fo readings taken at 3 or 7 days post-freeze treatment often correlate well with visual ratings previously described. However, in some cases, winter canola accessions that, over time, generate new shoots from the surviving stem suggest that visual ratings beyond 7 days can provide valuable information on the survival of some accessions.
Accomplishments
1. Winter oilseed cover crops help suppress establishment of weeds but few tolerate the freezing temperatures of northern climates. ARS scientists in Fargo, North Dakota, in collaboration with researchers at Kansas State University, evaluated the freezing tolerance of a winter canola breeding population totaling 413 accessions. Freezing studies done using state-of-the-art environmental chambers and development of high-throughput phenotyping methods confirmed suitable diversity within the germplasm collection. These phenotyping studies, in combination with genotyping, are a first step towards identifying markers useful in breeding programs aimed at developing winter canola germplasm with increased freezing tolerance.
Review Publications
Chao, W.S., Dogramaci, M., Horvath, D.P., Anderson, J.V., Foley, M.E. 2016. Phytohormone balance and stress-related cellular responses are involved in the transition from bud to shoot growth in leafy spurge. Biomed Central (BMC) Plant Biology. 16:47. https://doi.org/10.1186/s12870-016-0735-2.
Dogramaci, M., Gramig, G.G., Anderson, J.V., Chao, W.S., Foley, M.E. 2016. Field application of glyphosate induces molecular changes affecting vegetative growth processes in leafy spurge. Weed Science. 64(1):87-100. https://doi.org/10.1614/WS-D-15-00108.1.
Howe, G.T., Horvath, D.P., Dharmawardhana, P., Priest, H.D., Mockler, T.C., Strauss, S.H. 2015. Extensive transcriptome changes during natural onset and release of vegetative bud dormancy in Populus. Frontiers in Plant Science. 6:989. https://doi.org/10.3389/fpls.2015.00989.
Horvath, D.P., Hansen, S.A., Moriles-Miller, J.C., Pierik, R., Yan, C., Clay, D.E., Scheffler, B., Clay, S.A. 2015. RNAseq reveals weed-induced PIF3-like as a candidate target to manipulate weed stress response in soybean. New Phytologist. 207:196-210. https://doi.org/10.1111/nph.13351.
Foley, M.E. 2016. Germination of leafy spurge (Euphorbia esula L.) seeds under alternating temperatures: the effects of amplitude, midpoint, and imbibition in gibberellic acid. Canadian Journal of Plant Science. 96:321-328.
Carvalho, L.J.C.B., Agustini, M.A.V,, Anderson, J.V., Vieria, E.A., de Souza, C.R.B., Chen, S., Schaal, B.A., Silva, J.P. 2016. Natural variation in expression of genes associated with carotenoid biosynthesis and accumulation in cassava (Manihot esculenta Crantz) storage root. Biomed Central (BMC) Plant Biology. 16:133. https://doi.org/10.1186/s12870-016-0826-0.
