Source: UNIVERSITY OF CALIFORNIA, DAVIS submitted to NRP
REPRODUCTIVE BIOLOGY AND PHENOLOGY OF WEEDS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
1019008
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Apr 23, 2019
Project End Date
Sep 30, 2023
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
UNIVERSITY OF CALIFORNIA, DAVIS
410 MRAK HALL
DAVIS,CA 95616-8671
Performing Department
Plant Sciences
Non Technical Summary
This project supports the mission of the Agricultural Experiment Station by addressing the Hatch Act area(s) of: plant and animal production, protection, and health; sustainable agriculture.Weeds pose a major threat to global food security, biodiversity, ecosystem services and human health (e.g. allergenic weeds) with economic losses exceeding $27 billion annually in the US. Current weed control methods that heavily rely on the use of chemicals are not sustainable: herbicides are sprayed on >90% of the US croplands and account for 60% of the total expenditure on pesticides in the US. The current increasing trend in number of resistance cases, in particular resistance to glyphosate (Roundup, the world's most used herbicide) means that agriculture is rapidly losing its primary tool for weed control. To design sustainable agroecosystems that are resilient to weed invasions, we must adopt a multifaceted approach that incorporates ecological principles into weed management practices. This project attempts to test the viability of a novel approach for managing weeds that exploits a demographic handicap inherited with a unisexual breeding system. Most weeds, like other plants, are hermaphrodite i.e. a single plant harbors both the male and female organs. However, some weeds are dioecious i.e. some plants have only male flowers while others bear only female flowers. While dioecy can increase genetic variation, seed production in a dioecious population stringently depends on the co-occurrence and flowering synchrony of the two genders. Although under genetic control, sex expression in most dioecious plants can be labile, varying in response to the environment in which the offspring are reared. Further, the observation of gender specialization in dioecious plants suggests that the same environmental cue can affect the growth and development of males and females differentially. It should therefore be possible to reduce seed production in a dioecious weed population by skewing the population towards one sex and/or increasing the flowering asynchrony between genders through the manipulation of the environment. We test this hypothesis using Palmer amaranth (A. palmeri) as a dioecious model system, a weed that has also been identified as one of the worst weeds in US agriculture and currently expanding its range in California.
Animal Health Component
30%
Research Effort Categories
Basic
50%
Applied
30%
Developmental
20%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2132300114050%
2062300107030%
2012300108020%
Knowledge Area
206 - Basic Plant Biology; 201 - Plant Genome, Genetics, and Genetic Mechanisms; 213 - Weeds Affecting Plants;

Subject Of Investigation
2300 - Weeds;

Field Of Science
1070 - Ecology; 1080 - Genetics; 1140 - Weed science;
Goals / Objectives
The overarching goal is to contribute to diversification and development of ecological weed management strategies through a better understanding of the reproductive biology and phenology of weeds. To this end, this project integrates fundamental aspects of ecology, modeling, genomics and evolutionary biology to address the following objectives: • Decipher the genetic mechanism(s) underlying sex determination in Amaranthus palmeri as a model system of a weed with unisexual (dioecious) mode of reproduction• Examine the potential effects of environment on parental and progeny sex expression in A. palmeri by testing a wide range of factors including environmental stresses (drought, shading, nutrient deficit), phytohormones, and herbicides;• Determine the optimal sex ratio for seed production in A. palmeri and test for evidence of frequency-dependent sex expression;• Quantify the degree of flowering synchrony between male and female plants of A. palmeri and its relation to seed output under various environmental conditions;
Project Methods
Multiple approaches including field, laboratory and greenhouse experiments will be used to address the objectives of this project:+ Analysis of genomic DNA and mRNA sequence data from male and female A. palmeri+ Evaluating the sex specificity of the candidate genes in additional accessions+ Greenhouse studies on the effects of water stress on sex expression and flowering pattern+ Greenhouse studies on the effects of nutrient deficiency on sex expression and flowering pattern+ Greenhouse studies on the effects of light intensity on sex expression and flowering pattern+ Test of plant hormones on sex expression in cloned plants with pre-defined sexes+ Test of various male:female ratios on seed production to determine optimal sex ratio+ Examine sex ratio in natural populations of A. palmeri to test if it deviates from equity (50%:50%)+ Develop a demographic model that simulates the weed population dynamics as function of sex ration and flowering synchrony

Progress 10/01/19 to 09/30/20

Outputs
Target Audience: Nothing Reported Changes/Problems:Almost all our projects were affected by Covid-19: we had to terminate some experiments in the middle of measurements. One student had to change her project. PI Mesgaran also had health issues that slowed his work. What opportunities for training and professional development has the project provided? Students are being trained on how to identify sex of an Amaranthus palmeri seed using imaging techniques and machine learning/artificial intelligence. Students are being trained on how to test impact of plant hormones on sex expression in cloned plants with pre-defined sexes. Students are being trained on how to irradiate plant pollens and how to store irradiated pollens Postdoc and graduate students became familiar with machine learning techniques A visiting scholar from Israel was hosted in the lab How have the results been disseminated to communities of interest? scientific peer-reviewed journals teaching at the UC Cooperative Extension Weed Science School UC Davis Weed Blog and other social media UC Research and Information Centers (RICs), Weed and Rangelands RICs presentations at: UC-Davis Weed Day California Weed Science Society Weed Science Society of America Western Society of Weed Science What do you plan to do during the next reporting period to accomplish the goals? Decipher the genetic mechanism(s) underlying sex determination in Amaranthus palmeri as a model system with unisexual mode of reproduction Examine the potential effects of more environmental factors (allelochemicals, species competitions, shading, nutrient deficit, hormones, and herbicides) on parental and progeny sex expression, seed characteristics and phenology in A. palmeri. Develop a robotic pollinator for artificial pollination of A. plameri with irradiated pollen as new weed control technique

Impacts
What was accomplished under these goals? Identification of impact of environmental water stress, elevated temperatures and CO2 on offspring seed characteristics, sex expression, and phenology. Identification of differential response of Amaranthus palmeri offsprings to herbicides as dictated by differences in environmental water conditions of the parents. Identification of irradiation as a novel weed management tool for pollen sterility First evidence of sex chromosomes in Palmer amaranth

Publications

  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Neves, C. J., M. Matzrafi, M. Thiele, A. Lorant, M. B. Mesgaran, M. G. Stetter. Male linked genomic regions determine sex in dioecious Amaranthus palmeri. Journal of Heredity, DOI: https://doi.org/10.1093/jhered/esaa047
  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Matzrafi, M., O. Osipitan, S. Ohadi, M. B. Mesgaran. Under pressure: Maternal effects promote drought tolerance in progeny seed of Palmer amaranth (Amaranthus palmeri). Weed Science, DOI: https://doi.org/10.1017/wsc.2020.75


Progress 04/23/19 to 09/30/19

Outputs
Target Audience: Scientific community spanning from weed scientists to plant biologists Students Growers Ag industry e.g. agrochemical companies State representatives Changes/Problems:PI Mesgaran has had several health issues over the past period which has negatively impacted his work. He will be going through a full health examination in upcoming months and depending on the outcome he may apply for a medical leave. What opportunities for training and professional development has the project provided?One PhD student started working on this project through which she gained experience and skills in growing plants for experminet, cloning Palmer amaranth, hormom application, as well as working with Scanning Electron Microscopy and disecting microscopy. Another PhD student also rotated in the lab and gained similar researhc experiences. Two undergraduates also worked on this project partially. One of them got experieince in working with plants while the other did some computer programming. Two postdocs also partially worked on various aspect of the project: one left the lab for a premanent position in Israel while the second postdoc is helping the graduate and undergraduate studentswith this project. How have the results been disseminated to communities of interest?Both the PI Mesgaran, students and posdocs have presented the findings of this project at various conferences and workshops such as: Weed Science Society of America Canadian Weed Science Society California Weed Science Society UC Davis Weed Day One paper is currently under review in Royal B and another one is almost ready to submit. What do you plan to do during the next reporting period to accomplish the goals? Decipher the genetic mechanism(s) underlying sex determination in Amaranthus palmeri as a model system with unisexual mode of reproduction Examine the potential effects of more environmental factors (allelochemicals, species competitions, shading, nutrient deficit, hormones, and herbicides) on parental and progeny sex expression, seed characteristics and phenology in A. palmeri. Publish the findings (there are two more papers in preperation)

Impacts
What was accomplished under these goals? First evidence of sex lability in Palmer amaranth in response to water stress Found that flowering synchrony between male and female plants of Palmer amaranth can be reduced under water stress Scanning electron microscopy showed no evidence of vestigial tissues of the opposite sexes in male and female flowers of Palmer amaranth Found that maternal water conditions have marked influence on the progeny seed characteristics and their subsequent phenology Found millions of SNPs that differ between male and female plants of Palmer amaranth Identification of differential response of Amaranthus palmeri offspring to herbicides as dictated by differences in environmental water conditions of the parents

Publications

  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2019 Citation: Matzrafi, M, S. Ohadi, M. Mesgaran. 2019. Exploitation of Sex for Weed Management. Weed Science Society of America (WSSA) Annual Meeting, New Orleans, Jan 2019
  • Type: Journal Articles Status: Under Review Year Published: 2020 Citation: Mesgaran, M.B., Matzrafi, M. and Ohadi, S., 2020. Sex Lability and Dimorphism in Dioecious Palmer Amaranth (Amaranthus palmeri). Proceedings of the Royal Society B: Biological Sciences