DOCSLIB.ORG

Suppression of Phytophthora Capsici Infection and Promotion of Tomato Growth by Soil Bacteria

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Suppression of Phytophthora Capsici Infection and Promotion of Tomato Growth by Soil Bacteria Author’s Accepted Manuscript Suppression of Phytophthora capsici infection and promotion of tomato growth by soil bacteria Sharifah Farhana Syed-Ab-Rahman, Yawen Xiao, Lilia C. Carvalhais, Brett J. Ferguson, Peer M. Schenk www.elsevier.com PII: S2452-2198(18)30139-3 DOI: https://doi.org/10.1016/j.rhisph.2018.11.007 Reference: RHISPH137 To appear in: Rhizosphere Received date: 28 October 2018 Revised date: 25 November 2018 Accepted date: 25 November 2018 Cite this article as: Sharifah Farhana Syed-Ab-Rahman, Yawen Xiao, Lilia C. Carvalhais, Brett J. Ferguson and Peer M. Schenk, Suppression of Phytophthora capsici infection and promotion of tomato growth by soil bacteria, Rhizosphere, https://doi.org/10.1016/j.rhisph.2018.11.007 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Suppression of Phytophthora capsici infection and promotion of tomato growth by soil bacteria Sharifah Farhana Syed-Ab-Rahman1*, Yawen Xiao1, Lilia C. Carvalhais2, Brett J. Ferguson3, Peer M. Schenk1 1Plant-Microbe Interactions Laboratory, School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland 4072 Australia. 2Centre of Horticultural Science, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Ecosciences Precinct, GPO Box 267, Queensland 4001 Australia. 3Australian Research Council Centre of Excellence for Integrative Legume Research, The University of Queensland, St. Lucia, Queensland 4072, Australia. *Corresponding author: [email protected] Abstract Phytophthora capsici causes root, crown and fruit rot on many plant species including tomato and other solanaceous species. Plant growth promotion and suppression of P. capsici on tomato were assessed for three soil bacterial isolates, namely Bacillus amyloliquefaciens (UQ154), Bacillus velezensis (UQ156) and Acinetobacter sp. (UQ202). Cultures were applied as seed treatments (pre and post-infection inoculation) plus a soil drench at transplanting. The bacterial isolates significantly promoted growth of seedlings, as measured by root length, total fresh weight, and seedling vigor. We observed a reduction in pathogen load in tomato roots in both treatments using quantitative Polymerase Chain Reaction (qPCR). This work 1 confirms the broad-spectrum activity of these bacterial isolates for our previous findings of biocontrol activity on different plants. Keywords: Biocontrol; disease suppression; horticulture; Phytophthora capsici; tomato Phytophthora species cause devastating diseases to crops worldwide and are responsible for major production losses (Roy, 2015). Phytophthora blight caused by P. capsici has caused considerable economic losses to vegetable crops, including tomato, and prevalence of the disease has increased dramatically in the last decade (Lamour et al., 2012, Quesada-Ocampo & Hausbeck, 2010). The aim of this study was to evaluate the plant growth promotion and biocontrol activities of select soil bacteria against P. capsici in tomato. Among the high biodiversity of microorganisms, plant growth-promoting rhizobacteria (PGPR) play a crucial role in plant health and represent a potential alternative for a sustainable management of plant diseases suppression. Disease suppression in plants can occur through microbial antagonism or induction of resistance to pathogen infection (Van Loon, 2007, Liu et al., 2018, Gómez-Lama Cabanás et al., 2014). In our experience in disease suppression of chilli plants infected with P. capsici, the bacterial antagonists investigated had different modes of action and their application in soil resulted in better disease control (Syed-Ab-Rahman et al., 2018). It has been shown that non-pathogenic plant-associated microorganisms generally protect the plant by rapid colonization and thus exhausting the limited available substrates so that none are available for pathogens to develop (Heydari & Pessarakli, 2010). In most cases, pathogens are antagonized by the presence and activities of other microorganisms that they encounter. Bacterial isolates used in this study were originally obtained from bulk, and rhizosphere soil of Arabidopsis thaliana Col-0 plants grown in a potting mix and have previously been shown to have biocontrol activity in chilli (Capsicum annuum L., cultivar Cayenne) inoculated with 2 P. capsici, and promoted growth in lettuce (Syed-Ab-Rahman et al., 2018). The isolates were evaluated here for plant growth promotion in tomato (Solanum lycopersicum cultivar Red Cherry). Seeds were surface-sterilised by washing with 70% (v/v) ethanol (5 min), followed by 5% bleach (sodium hypochlorite) (5 min), and then rinsed five times with distilled water. Sterilised seeds were inoculated with the bacterial isolates by soaking for 1 h in phosphate 8 –1 buffer bacterial saline (PBS) suspensions containing cells at 1×10 CFU mL (OD600nm of 0.1). The isolates used were Bacillus amyloliquefaciens (UQ154), Bacillus velezensis (UQ156) and Acinetobacter sp. (UQ202) (Syed-Ab-Rahman et al., 2018). Seeds inoculated with PBS only were used as negative control. Inoculated seeds were planted in 80 mm × 80 mm, 410 mL, pots with three replicates and five pots per treatment. Soil moisture was maintained by spraying distilled water uniformly onto the soil. Trays were incubated in a growth cabinet (short day, eight h light) at 26°C for 21 days. We conducted pot assays to evaluate the ability of the rhizobacteria to suppress P. capsici infection in tomato. Two treatments were conducted: (i) bacterial inoculation prior to being challenged with the pathogen P. capsici (pre-infection inoculation) and (ii) bacterial inoculation after being challenged with the pathogen (post-infection inoculation). Seeds were inoculated with bacterial suspensions (OD600nm of 0.1) and re-inoculation was conducted (i) before and (ii) after pathogen challenge by soil drenching. Pathogen inoculation was performed by adding P. capsici zoospores solution in the tray at the bottom of the pots. Zoospores were prepared by placing P. capsici discs (5 mm diameter) of 6-day-old cultures grown on clarified V8 (cV8) agar into a petri dish containing a mixture of sterile distilled water and soil and incubated for three days under constant fluorescent light (40-W) to promote zoospores production (105 swimming zoospores mL−1 under haemocytometer at a ×100 magnification). The trays were filled with distilled water to maintain water-saturated conditions. Plants were harvested two weeks after bacterial/pathogen inoculation (four-week- 3 old) and the disease suppression ability of the bacterial isolates was assessed by real-time quantitative PCR (qPCR) analysis. DNA extraction of the washed root samples without attached soil and P. capsici primers used in this study were performed as we previously described (Syed-Ab-Rahman et al., 2018) and Act (Accession number: BT013707.1) was used as a plant reference gene which was amplified using the primers Act_F (5′- AGGCAGGATTTGCTGGTGATGATGCT-3) and Act_R (5′- ATACGCATCCTTCTGTCCCATTCCGA-3′). The relative P. capsici DNA biomass was normalized to Actin using the formula: 2^-(ΔCt P. capsici – ΔCt Actin). All bacterial isolates significantly increased the length of shoots (Figure 1A) and roots (Figure 1B), as well as the total fresh weight (Figure 1C) of the tomato plants. Increments of 10.9% in shoot and 45.8% in root lengths were obtained with B. amyloliquefaciens (UQ154) (Figure 1A) and B. velezensis (UQ156) inoculations, respectively. Only B. amyloliquefaciens (UQ154) led to a significantly higher total fresh weight compared with the uninoculated control (45.8%) (Figure 1C). Furthermore, all isolates were found to be effective in increasing seed germination rates and seedling vigour, with B. amyloliquefaciens (UQ154) exhibiting the highest effect on seedling vigour (Figure 1D). In general, plants respond differently to bacterial inoculation, often depending on the growth conditions (Asari et al., 2016). Our results also revealed that plants inoculated with the bacterial isolates harboured a lower pathogen load in roots. Interestingly, plants treated with bacterial isolates after challenge with P. capsici (post-treatment) (Figure 2B) exhibited significantly lower pathogen loads in roots compared to plants treated with bacterial isolates before pathogen challenge (pre-treatment) (Figure 2A). This suggests that sufficient number of bacteria need to be exposed to the pathogen to either produce bioactive compounds or elicit a response in plant for effective pathogen control. 4 The pathogen biomass in roots treated with the bacterial isolates were significantly lower than the untreated P. capsici-infected plants. Inoculation with P. capsici in the absence of bacterial treatments caused necrosis and brownish lesions throughout the primary root system in both treatments. However, upon inoculation of plants with bacterial isolates, necrosis and brown lesions were less frequent. All the isolates showed a similar reduction of disease severity on chili pepper plants (Table 1). Our results suggest that the bacterial isolates investigated here enhance plant growth, which can potentially result
Load more

Recommended publications
  • Phytophthora Blight of Cucurbits, Pepper, Tomato, and Eggplant - Thomas A
    Phytophthora Blight of Cucurbits and Peppers March 2021 Phytophthora blight, caused by an oomycete (Protist) Phytophthora capsici, is a serious threat to vegetable crops worldwide, particularly legumes, cucurbits and solanaceous plants. It is a fast spreading, aggressive disease, capable of causing complete crop destruction. Many vegetable growers are familiar with a close relative of this disease - late blight of potato and tomato, caused by Phytophthora infestans. In British Columbia (B.C.), it was first detected on pepper, pumpkin, squash, gourds, and eggplants in market gardens in Kelowna area in 2004; however, the disease has not been observed thereafter. In the USA, P. capsici is known to affect many crops, particularly in the eastern states. Hosts Phytophthora capsici is known to infect a wide range of vegetable crops, including crops belong to cucurbitaceae (e.g. melon, cucumber, pumpkin, squash), solanaceae (e.g. peppers, tomato, eggplant) and leguminosae (e.g. snap bean, lima bean), and many weeds. Under the laboratory conditions, it has been demonstrated to infect crops such as root crops (e.g. beet, carrot, radish, turnip, onion), greens (e.g. spinach, swiss-chard), legumes (e.g. alfalfa, soybean, snow pea) and okra. Symptoms Phytophthora capsici may affect all parts of the plant, causing a wide range of symptoms. It may cause pre- and post-emergence damping-off, stem and vine blight, wilting and fruit rot. Symptoms can appear as fast as 3 to 4 days after initial infection when temperatures are warm. Damping-off may occur both before and after emergence of seedlings in susceptible crops in the spring. Symptoms include a watery rot near the soil line, wilting, and subsequent plant death.
    [Show full text]
  • Managing Phytophthora Blight of Peppers and Cucurbits
    W 810 Managing Phytophthora Blight of Peppers and Cucurbits March 2019 Zachariah Hansen, Assistant Professor and Extension Specialist Timothy Siegenthaler, Graduate Assistant Andrew Swaford, Student Assistant Department of Entomology and Plant Pathology Disease Overview Phytophthora blight is a general term for crown rot, root rot and fruit rot of vegetables caused by the oomycete (water mold) Phytophthora capsici. It is a serious disease of peppers and cucurbits, but it can also afect other vegetables including tomato, eggplant and beans. The disease is best managed through prevention because once it becomes established in a feld it is nearly impossible to remove. The pathogen produces long-lived spores, called oospores, that can survive in the soil for 10 years or more. When con- ditions are warm and wet, the disease progresses rapidly through the production of another spore type called sporangia. When conditions are favorable for disease, millions of sporangia are produced, each releasing up to 40 swimming zoospores which are responsible for starting new infections. These spores move through splashing water and can easily spread down rows through fowing water or contaminate irrigation sources during rain events. 1 Managing Phytophthora Blight of Peppers and Cucurbits Diagnosing Phytophthora blight Peppers Symptoms on peppers include sudden wilting and dark lesions near the soil line (Fig. 1). Root rot may also be observed. Fruit are commonly afected and display a tan, water-soaked soft rot with a thin layer of white powdery mold visible to the naked eye (Fig. 2). Afected plants will often die shortly after symptoms appear. Symptoms of Phytophthora blight on pepper may be confused with southern blight, which also presents rapid wilting and a dark lesion as the soil line.
    [Show full text]
  • Molecular Diagnostics and Detection of Oomycetes on Fiber Crops
    plants Review Molecular Diagnostics and Detection of Oomycetes on Fiber Crops Tuhong Wang 1 , Chunsheng Gao 1, Yi Cheng 1 , Zhimin Li 1, Jia Chen 1, Litao Guo 1 and Jianping Xu 1,2,* 1 Institute of Bast Fiber Crops and Center of Southern Economic Crops, Chinese Academy of Agricultural Sciences, Changsha 410205, China; [email protected] (T.W.); [email protected] (C.G.); [email protected] (Y.C.); [email protected] (Z.L.); [email protected] (J.C.); [email protected] (L.G.) 2 Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada * Correspondence: [email protected] Received: 15 May 2020; Accepted: 15 June 2020; Published: 19 June 2020 Abstract: Fiber crops are an important group of economic plants. Traditionally cultivated for fiber, fiber crops have also become sources of other materials such as food, animal feed, cosmetics and medicine. Asia and America are the two main production areas of fiber crops in the world. However, oomycete diseases have become an important factor limiting their yield and quality, causing devastating consequences for the production of fiber crops in many regions. To effectively control oomycete pathogens and reduce their negative impacts on these crops, it is very important to have fast and accurate detection systems, especially in the early stages of infection. With the rapid development of molecular biology, the diagnosis of plant pathogens has progressed from relying on traditional morphological features to the increasing use of molecular methods. The objective of this paper was to review the current status of research on molecular diagnosis of oomycete pathogens on fiber crops.
    [Show full text]
  • Vegetable Notes for Vegetable Farmers in Massachusetts
    University of Massachusetts Extension Vegetable Notes For Vegetable Farmers in Massachusetts Volume 26, Number 6 May 15, 2014 IN THIS ISSUE: CROP CONDITIONS Crop Conditions Field planting continued steadily this week. In northern New England fields Pest Alerts have been slow to dry out, but farther south, wet soils have not been a barrier for the most part. The short Mother’s Day hot spell boosted crop growth as well as Preparing for Phytophthora capsici plant sales. Overall, crop growth continues to be slow in response to cool tem- Leafminer on Spinach peratures and cloudy skies. Growers are using season extension tools more than Summer Nitrogen Management ever, including seeding sweet corn under plastic later than usual, and covering large fields of early brassicas to push them along. Some growers are waiting to Fungicide Resistance Management transplant early squash, cukes and other for Cucurbit Diseases fruiting crops, while others are taking Events & Classes the chance that row cover or plastic low tunnels will provide protection from cold or wind. High tunnel greens are also slow. June market goals are looming – whether at the farmstand, farmers market, wholesale accounts, or CSA farmshares - and crops aren’t quite keeping up. Asparagus harvest started about a week late but is now in full swing. Rhu- barb and fiddleheads are also being harvested. Spring pests are up and running, including maggot flies, flea beetles, spinach and beet leaf miner, and Botrytis – see pest alerts. It’s almost time to start monitoring for ECB, The New England Crop Weather weekly report gives GDD from across the five CEW, and squash vine borer.
    [Show full text]
  • Pepper & Eggplant Disease Guide
    Pepper & Eggplant Disease Guide Edited by Kevin Conn Pepper & Eggplant Disease Guide* A PRACTICAL GUIDE FOR SEEDSMEN, GROWERS AND AGRICULTURAL ADVISORS Editor Kevin Conn Contributing Authors Supannee Cheewawiriyakul; Chiang Rai, Thailand Kevin Conn; Woodland, CA, USA Brad Gabor; Woodland, CA, USA John Kao; Woodland, CA, USA Raquel Salati; San Juan Bautista, CA, USA All authors are members of the Seminis® Vegetable Seeds, Inc.’s Plant Health Department. 2700 Camino del Sol • Oxnard, CA 93030 37437 State Highway 16 • Woodland, CA 95695 Last Revised in 2006 *Not all diseases affect both peppers and eggplants. Preface This guide provides descriptions and photographs of the more commonly found diseases and disorders of pepper and eggplant worldwide. For each disease and disorder, the reader will find the common name, causal agent, distribution, symptoms, conditions necessary for disease or symptom development, and control measures. The photographs illustrate characteristic symptoms of the diseases and disorders included in this guide. It is important to note, however, that many factors can influence the appearance and severity of symptoms. The primary audience for this guide includes pepper and eggplant crop producers, agricultural advisors, farm managers, agronomists, food processors, chemical companies and seed companies. This guide should be used in the field as a quick reference for information about some common pepper and eggplant diseases and their control. However, diagnosis of these diseases and disorders using only this guide is not recommended nor encouraged, and it is not intended to be substituted for the professional opinion of a producer, grower, agronomist, pathologist and similar professional dealing with this specific crop.
    [Show full text]
  • Ecologically Based Approaches to Management of Phytophthora Blight on Bell Pepper
    Jean Beagle Ristaino North Carolina State University, Raleigh Stephen A. Johnston Rutgers Agricultural Research and Extension Center, Bridgeton, NJ Symptoms and Life Cycle P. capsici can infect virtually every part of the pepper plant. The pathogen causes a root and crown rot on pepper (Fig. 1) and also forms distinctive black lesions on the Ecologically Based stem (Fig. 2). P. capsici can also infect the leaves and causes lesions that are circular, grayish brown, and water-soaked (Fig. 3). Leaf lesions and stem lesions are common Approaches to when inoculum is splash dispersed from the soil to lower portions of the plant. The pathogen can also infect fruit and causes Management lesions that are typically covered with white sporangia, a sign of the pathogen (Fig. 4). P. capsici typically causes a fruit of Phytophthora Blight rot or stem rot on cucumbers and squash (Fig. 5). P. capsici reproduces by both sexual and asexual means (Fig. 6). The pathogen pro- on Bell Pepper duces two mating types, known as the A1 and A2. These are actually compatibility types and do not correspond to dimorphic forms. Each mating type produces hor- mones that are responsible for gametangia differentiation in the opposite mating type. Both A1 and A2 mating types are common Phytophthora blight, caused by the oo- input of knowledge concerning a pathogen in fields in North Carolina and have also mycete pathogen, Phytophthora capsici, is life cycle, and secondarily, when necessary, been identified within the same plant (59). a devastating disease on bell pepper and on physical, chemical, and biological sup- P.
    [Show full text]
  • The Oomycete Broad-Host-Range Pathogen Phytophthora Capsici
    MOLECULAR PLANT PATHOLOGY (2012) 13(4), 329–337 DOI: 10.1111/J.1364-3703.2011.00754.X Pathogen profile The oomycete broad-host-range pathogen Phytophthora capsici KURT H. LAMOUR1, REMCO STAM2,3, JULIETTA JUPE3 AND EDGAR HUITEMA3,* 1Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA 2Plant Pathology Programme, James Hutton Institute, Errol Road, Invergowrie, Dundee DD2 5DA, UK 3Division of Plant Science, College of Life Sciences, University of Dundee at JHI, Errol Road, Invergowrie, Dundee DD2 5DA, UK ally, hyphae do not emerge from infected plants or fruit SUMMARY (common with Pythium infections) and all that is visible on the Phytophthora capsici is a highly dynamic and destructive patho- surface of an infected plant is sporangia. gen of vegetables. It attacks all cucurbits, pepper, tomato and Importance: Phytophthora capsici presents an oomycete worst- eggplant, and, more recently, snap and lima beans. The disease case scenario to growers as it has a broad host range, often incidence and severity have increased significantly in recent produces long-lived dormant sexual spores, has extensive geno- decades and the molecular resources to study this pathogen are typic diversity and has an explosive asexual disease cycle. It is growing and now include a reference genome. At the population becoming increasingly apparent that novel control strategies are level, the epidemiology varies according to the geographical loca- needed to safeguard food production from P. capsici and other tion, with populations in South America dominated by clonal oomycetes. Considering that P. capsici is easy to grow, mate and reproduction, and populations in the USA and South Africa com- manipulate in the laboratory and infects many plant species, this posed of many unique genotypes in which sexual reproduction is pathogen is a robust model for investigations, particularly those common.
    [Show full text]
  • Mhora Udel 0060D 13546.Pdf
    A GENOMICS BASED APPROACH TO MANAGING DOWNY MILDEW OF LIMA BEAN by Terence Tariro Mhora A dissertation submitted to the Faculty of the University of Delaware in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Plant and Soil Sciences Fall 2018 © 2018 Terence Tariro Mhora All Rights Reserved A GENOMICS BASED APPROACH TO MANAGING DOWNY MILDEW OF LIMA BEAN by Terence Tariro Mhora Approved: __________________________________________________________ Erik Ervin, Ph.D. Chair of the Department of Plant and Soil Sciences Approved: __________________________________________________________ Mark Rieger, Ph.D. Dean of the College of Agriculture and Natural Resources Approved: __________________________________________________________ Douglas J. Doren, Ph.D. Interim Vice Provost for the Office of Graduate and Professional Education I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Nicole M. Donofrio, Ph.D. Professor in charge of dissertation I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Thomas A. Evans, Ph.D. Professor in charge of dissertation I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Randall J. Wisser, Ph.D. Member of dissertation committee I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy.
    [Show full text]
  • Diversity and Management of Phytophthora in Southeast Asia
    Diversity and Management of Phytophthora in Southeast Asia Editors: André Drenth and David I. Guest Australian Centre for International Agricultural Research Canberra 2004 Diversity and Management of Phytophthora in Southeast Asia Edited by André Drenth and David I. Guest ACIAR Monograph 114 (printed version published in 2004) The Australian Centre for International Agricultural Research (ACIAR) was established in June 1982 by an Act of the Australian Parliament. Its mandate is to help identify agricultural problems in developing countries and to commission collaborative research between Australian and developing country researchers in fields where Australia has a special research competence. Where trade names are used this constitutes neither endorsement of nor discrimination against any product by the Centre. ACIAR MONOGRAPH SERIES This peer-reviewed series contains the results of original research supported by ACIAR, or material deemed relevant to ACIAR’s research objectives. The series is distributed internationally, with an emphasis on developing countries. © Australian Centre for International Agricultural Research, GPO Box 1571, Canberra, ACT 2601, Australia Drenth, A. and Guest, D.I., ed. 2004. Diversity and management of Phytophthora in Southeast Asia. ACIAR Monograph No. 114, 238p. ISBN 1 86320 405 9 (print) 1 86320 406 7 (online) Technical editing, design and layout: Clarus Design, Canberra, Australia Printing: BPA Print Group Pty Ltd, Melbourne, Australia Diversity and Management of Phytophthora in Southeast Asia Edited by André Drenth and David I. Guest ACIAR Monograph 114 (printed version published in 2004) Foreword The genus Phytophthora is one of the most important plant pathogens worldwide, and many economically important crop species in Southeast Asia, such as rubber, cocoa, durian, jackfruit, papaya, taro, coconut, pepper, potato, plantation forestry, and citrus are susceptible.
    [Show full text]
  • Phytophthora Blight on Beans
    Appendix E Disease Alert PHYTOPHTHORA BLIGHT ON BEANS Phytophthora blight is a devastating disease caused by the water mold Phytophthora capsici. It is well known throughout the United States as a pathogen on solanaceous (bell pepper, hot pepper, eggplant, tomato) and cucurbit crops (cantaloupe, cucumber, gourd, honeydew melon, pumpkin, muskmelon, summer squash, watermelon, winter squash, zucchini), and in recent years has caused problems on snap and lima beans. Phytophthora blight was reported on lima beans in 2000 on crops grown in Delaware, Maryland, and New Jersey. In 2003, the disease was reported on snap beans in Michigan, and in 2008 on snap beans grown on Long Island. In 2009, a Phytophthora blight epidemic struck snap beans fields in Connecticut, resulting in devastating losses. Phytophthora blight symptoms on snap beans are as follows: P. capsici produces large water soaked lesions on the leaves, and as the disease progresses the infected leaves fall off the plant. Lesions on the stems are brown with white powdery areas. White lesions are produced on the pods, and infected areas shrivel and desiccate. Consumed pods are dry, shriveled and leathery. As the name suggests, this water mold thrives in moist environments. The Dillard Lab is conducting research to assess fungicide efficacy for disease control and to evaluate tolerance of several snap bean varieties to P. capsici. Snap bean pods infected with P. capsici turn white and are shriveled. Note senescing and dead leaves. Early stage of Phytophthora blight on snap bean pods and stems. Note premature senescing of infected leaves. .
    [Show full text]
  • Biologically Active Phytophthora Mating Hormone Prepared by Catalytic Asymmetric Total Synthesis
    Biologically active Phytophthora mating hormone prepared by catalytic asymmetric total synthesis Syuzanna R. Harutyunyan*†, Zhijian Zhao†‡§, Tim den Hartog*, Klaas Bouwmeester‡, Adriaan J. Minnaard*¶, Ben L. Feringa*¶, and Francine Govers‡¶ *Department of Organic Chemistry and Molecular Inorganic Chemistry, Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands; and ‡Laboratory of Phytopathology, Plant Sciences Group, Wageningen University, Binnenhaven 5, 6709 PD, Wageningen, The Netherlands Edited by Laura L. Kiessling, University of Wisconsin, Madison, WI, and approved April 7, 2008 (received for review September 30, 2007) A Phytophthora mating hormone with an array of 1,5-stereogenic centers has been synthesized by using our recently developed methodology of catalytic enantioselective conjugate addition of Grignard reagents. We applied this methodology in a diastereo- and enantioselective iterative route and obtained two of the 16 possible stereoisomers of Phytophthora hormone ␣1. These syn- thetic stereoisomers induced the formation of sexual spores (oospores) in A2 mating type strains of three heterothallic Phyto- phthora species, P. infestans, P. capsici, and P. nicotianae but not in A1 mating type strains. The response was concentration- dependent, and the oospores were viable. These results demon- strate that the biological activity of the synthetic hormone resem- bles that of the natural hormone ␣1. Mating hormones are essential components in the sexual life cycle of a variety of organisms. For plant pathogens like Phytophthora, sexual repro- CHEMISTRY duction is important as a source of genetic variation. Moreover, the Fig. 1. Structure of mating hormone ␣1 (1) (A) and enantioselective CA of thick-walled oospores are the most durable propagules that can Grignard reagents to ␣, ␤-unsaturated thioesters (B).
    [Show full text]
  • Phytophthora
    PHYTOPHTHORA INTRODUCTION Phytophthora (from Greek (phyton) plant and (phthora) destruction the plant- destroyer) is a genus of plant-damaging oomycetes (water moulds) whose member species are capable of causing enormous economic losses on crops worldwide as well as environmental damage in natural ecosystem. The cell wall of Phytophthora is made up of cellulose. The genus was first described by Heinrich Anton de Bary in 1875. Approximately 170 species have been described although 100–500 undiscovered Phytophthora species are estimated to exist. Phylum: Oomycota Order: Peronosporales Family: Peronosporaceae Genus: Phytophthora PATHOGENICITY Phytophthora spp. is mostly pathogens of dicotyledons, and many are relatively host-specific parasites. Phytophthora cinnamomi, though, infects thousands of species ranging from club mosses, ferns, cycads, conifers, grasses, lilies, to members of many dicotyledonous families. Many species of Phytophthora are plant pathogens of considerable economic importance. Phytophthora infestans was the infective agent of the potato blight that caused the Great Famine of Ireland, and still remains the most destructive pathogen of solanaceous crops, including tomato and potato. The soya bean root and stem rot agent, Phytophthora sojae, has also caused longstanding problems for the agricultural industry. In general, plant diseases caused by this genus are difficult to control chemically, thus the growth of resistant cultivars is the main management strategy. Other important Phytophthora diseases are: Phytophthora
    [Show full text]