California Fruit and Vegetable

Tag: NIFA

  • Novel Technology May Lead to Improved Citrus Varieties

    Developing disease-resistant, high-quality improved crop varieties to benefit agricultural producers and consumers may seem like a “hairy” task, but Texas A&M AgriLife Research scientists may have gotten to the root of the issue.

    A new biological technology that develops and multiplies disease-resistant citrus plants using “hairy roots” is under development by an AgriLife Research team led by Kranthi Mandadi, Ph.D. Mandadi is an AgriLife Research associate professor at the Texas A&M AgriLife Research and Extension Center at Weslaco and a faculty member of the Department of Plant Pathology and Microbiology and the Institute for Advancing Health Through Agriculture in Bryan-College Station.

    At the root of their project is developing new ways to fight fastidious pathogens, which infect living plants and resist growth in a lab setting for study. One such fastidious pathogen causes citrus greening — a significant problem for the citrus industry.

    Since 2021, Mandadi has spearheaded a $7 million U.S. Department of Agriculture National Institute of Food and Agriculture, multi-state Coordinated Agricultural Project that is also a designated NIFA Center of Excellence to combat citrus greening.

    “Fastidious plant pathogens infect citrus, tomatoes, potatoes, grapes, peppers and other crops grown throughout Texas,” said Dirk Hays, Ph.D., director of the Texas A&M AgriLife center at Weslaco. “Often transmitted by insect vectors, these disease agents are responsible for billions of dollars in agricultural losses yearly.”

    A breakthrough in plant disease therapies

    The U.S. Department of Agriculture estimates the citrus industry would prevent $3 billion in losses per year by controlling citrus greening alone.

    Assay plate of “hairy roots” that may be used to develop improved varieties of citrus and other plants. (Texas A&M AgriLife photo)

    In recent years, Mandadi and his team at Weslaco developed a breakthrough method as an alternative means to propagate fastidious bacteria responsible for citrus greening and other insect-vectored diseases such as potato zebra chip and tomato vein greening disease.

    “We developed a technology that uses pathogen-infected host tissues to produce so-called ‘hairy roots’ that can serve as biological vessels for the propagation of these pathogens in the laboratory,” Mandadi said.

    The hairy root screening technique has already led to the discovery of new antimicrobial peptides and chemicals with proven efficacy in plant materials, said Sonia Irigoyen, Ph.D., an AgriLife Research scientist who helped develop the hairy root technology.

    “These antimicrobials, either singly or in combination, could be used as near- and long-term therapies to control citrus greening, potato zebra chip and tomato vein greening diseases,” she said.

    Now, in their most recent study, Mandadi and his team investigated how to use this hairy root technique in plant transformation and bioengineering improved citrus.

    Hairy root-based genetic engineering of citrus

    Citrus plant regeneration from hairy roots. (Texas A&M AgriLife photo)

    Building on previous success, in their latest study called “Rhizobium rhizogenes-mediated hairy root induction and plant regeneration for bioengineering citrus,” recently published in the high-impact Plant Biotechnology Journal, Mandadi and his team showed proof of the concept of engineering citrus using hairy roots.

    In addition to Mandadi and Irigoyen, study co-authors include Manikandan Ramasamy, Ph.D., Michelle Dominguez, B.S., and Carmen Padilla, Ph.D., all AgriLife Research scientists at Weslaco. The study was supported by grants from the U.S. Department of Agriculture, the Foundation for Food and Agricultural Research, Texas A&M AgriLife Research Insect-Vectored Disease Seed Grants, and the Institute for Advancing Health Through Agriculture.

    “Developing new plant varieties with improved genetics using conventional breeding or the latest bioengineering and CRISPR tools can be quite laborious, often taking multiple years,” Mandadi said. “The ability to overcome this bottleneck and improve this process, particularly for hardy, slow-growing, perennial trees like citrus, can be a game changer and a boon to producers and consumers.”

    A more efficient, quicker method for breeding hardier citrus

    In their most recent study, the researchers used R. rhizogenes to induce transgenic hairy roots from diverse citrus cultivars such as grapefruit, sweet orange, rough lemon and citron at efficiencies of 28% to 75%. This level of efficiency is at least twice — potentially greater — than those seen with previous methods for citrus transformation, making for a faster and less costly process.

    After making sure a transgenic root had the proper genetics, the team was then able to regenerate and clone several identical, transgenic plants from it.

    Ramasamy said while scientists have used multiple methods in the past to transform crops, the efficiency of genetic modification of tree crops like citrus has been challenging due to their slow growth and difficulties in regeneration.

    “However, we were able to demonstrate a versatile R. rhizogenes-mediated hairy root induction, plant regeneration and clonal propagation approach that could be helpful for multiple bioengineering and gene-editing applications in citrus and other tree crops,” he said.

    The proposed R. rhizogenes-mediated citrus hairy root induction, shoot regeneration and multiplication process achieved in about six months what typically took approximately 12-18 months using the previously described transformation method.

    “This means we will be able to develop and multiply disease-resistant citrus plants using root tissue more quickly and get them established much faster than when using the previous approaches,” Mandadi said. “The entire throughput for developing more disease-resistant citrus and other plants will be greatly expedited.”

    Mandadi said the hairy-root mediated transformation could benefit citrus producers in many ways by speeding the development of new varieties with superior disease resistance, as well as resilience to environmental stresses, increased production efficiency and improved nutritional quality.

    “It will also benefit the consumer in that they can expect to continue to have a supply of their favorite fruits and other items with characteristics they find most appealing in their produce,” he said.

  • New Nanoparticle-Based Sensors to Measure Residual Herbicides in Food

    Two newly developed, low-cost tests that use nanoparticles to detect chemicals can accurately measure tiny amounts of two potentially harmful herbicides in fruits, vegetables and their products.

    Reporting in the journal Food Chemistry, a Washington State University research team used two testing methods to measure the levels of two herbicides, namely atrazine and acetochlor, in samples of apples, strawberries, cabbage, corn and fruit juices. The work shows the real-world viability of their easy-to-use and inexpensive methods of testing.

    “We applied this technology for real sample detection – which is an important step in moving towards commercialization,” said Annie Du, research professor in WSU’s School of Mechanical and Materials Engineering and the principle investigator of the project.

    Annie Du

    The Food and Drug Administration (FDA) regularly tests a broad range of commodities for approximately 800 pesticide residues, and producers are required to keep the chemical residues on food below a certain level that is considered safe. The two herbicides the researchers measured are widely used in crop production in the U.S. At high exposures, they are potentially toxic for people and have been linked to a range of maladies from allergies to hormone disruption to cancer.

    Doing the testing, however, currently requires sophisticated and expensive instruments as well as a trained technician.

    “We want to come up with a low-cost method that can be used in the field or in the laboratory,” said Bernie Van Wie, corresponding author on the paper and a professor in WSU’s Gene and Linda Voiland School of Chemical Engineering and Bioengineering.

    Bernie Van Wie

    In the past few years, the researchers have developed and patented their idea that uses nanoparticles of palladium and platinum to amplify the signal of molecules. The nanoparticles attach to an antibody, which recognizes the chemical, and then stimulate the production of a signal.  The amplification allows the researchers to know that tiny amounts of the chemicals are present and at what level.

    In this latest work, the researchers used the nanoparticles in two types of tests to measure two chemicals simultaneously. The chemicals were spiked into fruit and vegetable samples that were pureed in a blender.

    One of the tests uses the palladium-platinum nanoparticles to catalyze a reaction that causes a color change in a sample when the herbicide is present. The test can be done using a small unit that can be carried into the field.  The other test the researchers developed uses the nanoparticle in a low-cost paper strip that looks like a COVID-19 or pregnancy test and can be read with a smartphone reader.

    The tests were sensitive enough to measure the chemicals down to the maximum acceptable levels and were validated using traditional testing methods.

    “We’re actually able to detect below the maximum concentration limits. If there’s any pesticide or herbicide in the sample,” said Van Wie. “That’s good because while this can be done by other methods, this method is low-cost and portable in the field.”

    Du has recently started a company that is negotiating with WSU’s Office of Commercialization to license the technology for additional applications. The work was supported by the USDA/National Institute of Food and Agriculture (NIFA) Agriculture and Food Research Initiative (AFRI) program (grant number 2018-67021-27970). — By Tina Hilding, Voiland College of Engineering and Architecture, Washington State University

  • May is National Salad Month, Celebrate with More US Grown Salad on the Table

    What is arguably the foundational ingredient in salad? Lettuce! USDA’s National Institute of Food & Agriculture (NIFA) supports research that is leading to stronger, healthier, more disease-resistant lettuce cultivars. See what NIFA is doing to keep healthy, safe salads on the menu for consumers everywhere.

    Current funded projects in California and Illinois include the following:

    The USDA Agricultural Research Service, Pacific West Area, in Albany, California, is working to improve the safety and survival of lettuce during fresh-cut processing and cold storage. Mechanical damage of processed leaf tissue offers new opportunities for the proliferation of E. coli, the main bacterial agent that causes lettuce-linked foodborne outbreaks. Researchers are working to identify lettuce cultivars that effectively reduce population sizes of E. coli upon shredding and cold storage and characterize defense responses on cut tissue.

    The USDA Agricultural Research Service in Berkeley, California, is studying the prevention of pathogen contamination in agriculture water in lettuce production. Researchers are developing and implementing a screening tool to test the effectiveness of sanitizer, antimicrobial resistance and tolerance to oxidizing compounds, and provide recommendations on keeping resistant strains from developing.

    The University of California – Davis is enhancing the use of resources to increase sustainable lettuce production in changing climates. This research project seeks to improve water, nitrogen and phosphate use in lettuce, and determine heat/cold/saline tolerance, to improve lettuce’s resilience. The research findings will be shared with breeders and students.

    The University of Chicago is modifying lettuce by altering its genetic makeup without introducing genetically modified genes. Researchers are using tiny fibers to inject substances that will enable changing the gene content of lettuce.

  • NIFA Invests Nearly $11M to Combat & Prevent Citrus Greening Disease

    The U.S. Department of Agriculture’s (USDA) National Institute of Food and Agriculture (NIFA) announced an investment of nearly $11 million for research to combat Huanglongbing (HLB), commonly known as citrus greening disease. HLB, caused by an insect bacterium, is the most severe threat to global citrus production.

    “NIFA’s Emergency Citrus Disease Research and Extension program brings the nation’s top scientists together with citrus industry representatives to find scientifically sound solutions to combat and prevent HLB at the farm-level,” said NIFA Director Dr. Carrie Castille. “This year’s awards represent all three major U.S. citrus growing regions and include possible solutions ranging from blocking HLB transmission from inside the insect vector to utilizing novel anti-microbial peptides to treat HLB-infected trees.”

    The fiscal year 2021 five funded Emergency Citrus Disease Research and Extension projects include:

     

    • Texas A&M AgriLife Research will leverage public-private partnerships between state agencies, universities, USDA’s Agricultural Research Service, and the citrus industry to pursue advanced testing and commercialization of promising HLB therapies and extend outcomes to stakeholders. ($7,000,000)
    • University of California, Riverside will build on previous work and evaluate the performance of 300 hybrid citrus trees in established trials to map HLB tolerance/resistance genes and release superior new rootstocks. ($1,499,998)
    • University of Florida seeks to develop a bacterial pathogen transmission blocking strategy (specifically to block Candidatus Liberibacter asiaticus, the pathogen that causes HLB) toward mitigation of citrus greening-related losses in an integrated pest management framework. ($1,020,810)
    • University of Florida’s project will support the needs of both commercial and residential citrus growers by comparing new tools to support young trees and develop management recommendations for the incorporation of each tool into production and residential settings. ($750,000)
    • University of Florida aims to introduce and transfer the natural HLB resistance present in Australian limes into conventional citrus to produce HLB-resistant Australian lime hybrid rootstocks and deploy these hybrids to protect susceptible citrus scions against HLB. ($500,000)

    Background: Huanglongbing (HLB) is considered the most destructive disease in citrus growing regions worldwide and has become the greatest challenge for the U.S. citrus industry. Currently, HLB has no cure.  Since HLB’s initial U.S. detection in 2005, citrus acreage and production in Florida has decreased by 60 percent and 80 percent, respectively. The disease has spread to all citrus-producing states, including Texas and California. Although citrus greening is a serious threat to the citrus industry worldwide, significant progress has been made to coordinate a multipronged approach for citrus greening management and suppression of the Asian citrus psyllid, an insect that carries and spreads HLB, through expanding partnerships with USDA’s Animal and Plant Health Inspection Service, states, universities, and private partners.  Learn more about HLB.

    Asian Citrus Psyllid, the insect responsible for the spread of the citrus-killing disease HLB

    NIFA invests in and advances agricultural research, education, and Extension across the nation to make transformative discoveries that solve societal challenges. NIFA supports initiatives that ensure the long-term viability of agriculture and applies an integrated approach to ensure that groundbreaking discoveries in agriculture-related sciences and technologies reach the people who can put them into practice. In FY2020, NIFA’s total investment was $1.95 billion.

    Visit our website: www.nifa.usda.gov; Twitter: @USDA_NIFA; LinkedIn: USDA-NIFA.

  • Healthy Roots, Healthy Trees: HLB & Soil Microbes

    The rhizosphere, defined as the soil environment that surrounds the plant roots, is a rich and diverse habitat for microbes. Some members of the rhizosphere microbiome (or collection of microbes), are good, others bad while many are just there and don’t provide any benefits or harm to the host. One function of the good microbes in the rhizosphere is to help facilitate the availability and assimilation of nutrients and water from the rhizosphere. Just like the human gut, the plant rhizosphere conveys key nutritional functions and the analogy was made that “plants wear their gut on the outside”. One example is the symbiotic relationship between legumes (peas, beans) and rhizobia. Those bacteria help the plant fix atmospheric nitrogen in exchange for carbon supply. Another example is the symbiotic relationship between the plant and mycorrhizal fungi, whereby the mycorrhizae receive carbon from the plant in exchange for increased nutrient uptake (principally phosphorus and nitrogen). There is undeniable evidence that plants have developed a mechanism for recruiting good microbes to cope with environmental stress such as protection against opportunistic pathogens or drought. The rise of ‘omics’ technologies have helped profile entire microbial communities associated with plants and shed light in their biological functions. This research has fueled the development of novel commercial bioproducts to address the increasing consumer’s demand of environmentally-friendly products. As a result, there has been several commercial ‘probiotics’ and ‘prebiotics’ that have been marketed for agricultural use including many biocontrol agents such as fungal- (e.g., Trichoderma) and bacterial- based (e.g., Bacillus, Streptomyces, or Pseudomonas) bioproducts.

    One goal of my research program is to identify beneficial microbes for tree and vines crops, promote practices that support the presence and abundance of beneficial microbes and figure out how good microbes help combat pathogens and support plant health. As part of a collaborative project (UC Riverside, University of Florida, USDA-ARS) funded by the California Citrus Research Board and the USDA-NIFA, we profiled the microbiome of citrus trees in the context of Huanglongbing disease (or HLB). HLB is a highly destructive and lethal disease to all commercial citrus cultivars making it a threat to citrus production globally. Finding strategies that do not only rely exclusively on management of the insect vector of the bacterium (the Asian Citrus Psyllid), is a priority to the citrus industry. In our research, we found that there were significant tissue-specific microbial shifts occurring within the citrus microbiome as trees get sicker, especially in the root compartment. As HLB progressed, there were depletions of beneficial species in roots, such as mycorrhizal fungi, and enrichments of parasitic microorganisms, such as Fusarium and Phytophthora (see Figure). HLB-affected trees decline because of the clogging the phloem sieve tubes, which limit movement of sap and translocation of sugar to the roots, hence leading to feeder root collapse. Once tree is weakened, it becomes more susceptible to pathogens such as Phytophthora which further weakens the trees and exacerbate above ground HLB symptoms. In addition, several studies from Florida suggested that cultural practices that supported root health and rhizosphere microbiome richness and diversity limited root collapse.

    Figure: Citrus decline caused by HLB (https://apsjournals.apsnet.org/doi/10.1094/PBIOMES-04-20-0027- R – Ginnan et al. 2020. Phytobiomes); canopy thinning, wood dieback, feeder roots decline, collapse of beneficial microbes and enrichment of pathogens in roots.

    Our group was recently awarded another research funding by the USDA-NIFA Emergency Citrus Disease Research and Extension program (project director, M.C. Roper, Microbiology and Plant Pathology, UC Riverside). This research effort in collaboration with UC Agricultural and Natural Resources, UC Davis, University of Florida, and the USDA-ARS aims at investigating the root collapse associated with HLB- impacted trees and finding ways to mitigate it by promoting root health. In the proposed work, we will test how different sectors of the root microbiome contribute to or lessen fibrous root loss and if soil amendments (e.g., humic acid treatment, mulching) and planting of HLB tolerant rootstocks (Poncirus trifoliata and P. trifoliata hybrids) can be used to mitigate root loss associated with HLB in Florida, and how tree respond to those practices under a HLB free environment in California. While these approaches will not cure trees from HLB, it will provide a science-based information for strategies that support root and tree health and sustain orchard longevity until remedies are discovered. — By Philippe Rolsausen, Professor in Cooperative Extension, UC Riverside

  • University of Florida Awarded Grants to Continue Fight Against Citrus Greening

    University of Florida researchers hope to discover new methods to help citrus growers fight the deadly citrus greening (or Huanglongbing) disease with cost effective, long-term sustainable treatments with the support of recently awarded federal grants.  Three teams of scientists from UF’s Institute of Food and Agricultural Sciences received nearly $4.5 million in U.S. Department of Agriculture funds to study new ways to manage the invasive insect causing millions of damage to Florida’s citrus crops.

    “These grants build on an existing portfolio of success in finding solutions to combat citrus greening throughout Florida’s citrus groves,” said Michael Rogers, director of UF/IFAS Citrus Research and Education Center and coordinator of the UF/IFAS statewide citrus program. “They will contribute to the solutions we are providing that support citrus growers in sustainably and profitably growing citrus throughout the state.”

    Managing the Asian citrus psyllid with the environment in mind

    Bryony Bonning, eminent scholar and professor in entomology and nematology, leads a team from Gainesville and the UF/IFAS Citrus Research and Education Center in Lake Alfred, Florida in a project that uses a bacteria-derived pesticidal protein combined with gene silencing to manage the invasive Asian citrus psyllid (ACP) population. The long-term goal of the proposed work is to create an environmentally benign approach for citrus growers to control ACP that works within an integrated pest management (IPM) strategy. The project intends to identify the optimal components for an ACP control product for grower use.

    The grant project aims to: 1) optimize ACP-active proteins derived from the bacterium Bacillus thuringiensis (Bt) that suppress psyllid populations, 2) further develop genetic solutions that would disrupt ACP, and 3) screen for the best combination of these methods for use against ACP. On completion of this project, researchers will be well positioned to produce transgenic citrus and/or trap plants that will suppress ACP populations for use by citrus growers.

    This method of effective vector control, combined with other measures will help the citrus industry in Florida rebound, and protect the industries in California and Texas. The results of this research are anticipated to reduce the need for tree removal and replanting as well as reduce insecticide applications, and increase yields and fruit quality, contributing to the long-term profitability and sustainability of U.S. citrus production.

    Attacking citrus greening from the inside out

    Amit Levy, assistant professor of plant pathology, received a NIFA grant to examine how the Candidatus Liberibacter asiaticus (CLas) bacteria interacts with a narrow tissue – known as the phloem – which is buried inside the stem of the citrus tree. CLas resides in and plugs the phloem in the stem of the citrus tree, leading to inhibition of sugar and nutrient transport into the tree’s sink tissues, including the fruit. Eliminating these plugs can presumably result in renewed sugar transport and increased fruit yields.

    However, there is a significant gap in understanding CLas-phloem interactions in citrus, which has been a major limiting factor for controlling the disease. Levy and a team of UF/IFAS researchers and Sainsbury lab and Cornell University scientists plan to address these challenges with a novel seed coat-based system that supports in-depth analyses of phloem dynamics and CLas-phloem interactions in HLB-affected citrus. The project will identify key players required for phloem plugging, host immune response and CLas colonization inside the phloem. These key players can later become novel targets for manipulation with gene editing techniques that can be translated into usable products, such as transgene-free CRISPR/Cas9 edited plants to block the disease propagation and movement, and increase sugar and nutrient translocation into fruit thus increasing tolerance or resistance to HLB.

    A Novel Therapeutic Strategy For HLB-Infected Trees

    Huanglongbing (HLB)-resistant or tolerant citrus trees are the long-term solution for citrus greening disease.  Existing research has generated transgenic citrus lines that provide robust tolerance to HLB. These transgenic lines are already in field tests as a potential management possibility for HLB. However, these trees will have to go through an extensive approval process before being made available to growers.

    A research team lead by UF/IFAS microbiology and cell science professor Zhonglin Mou and faculty from the UF/IFAS Citrus Research and Education Center and UF/IFAS Southwest Research and Education Center are working to speed up this process by reproducing the greening resistant or tolerant genetic makeup in non-transgenetically modified plants by gene editing using CRISPR/Cas9. This is a better long-term approach but will take time.

    The primary goal of this project is to develop an interim treatment for HLB. The project hopes to turn off the genes that negatively control the citrus immune system and result in disease symptoms in citrus when exposed to disease-causing pathogens. Coupled with other work to target the HLB-causing bacterium itself, the overall goal is to develop new management strategies making citrus varieties highly tolerant to this disease. The project will use a vector derived from citrus tristeza virus (CTV) to remove negative regulation of the citrus immune system, leading to improved immune response and HLB tolerance. The same CTV vector will also deliver antimicrobial peptides to reduce HLB pathogens.

    The synergism between the immune system-provided tolerance and the antimicrobial peptide-mediated pathogen reduction is expected to provide effective control of the HLB disease. Importantly, CTV naturally occurs in the field and does not make genetic changes to the citrus genome, and thus the employed strategy is a non-transgenic approach. — By Ruth Borger, University of Florida

    The mission of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS brings science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents.