Link to home
APS
Membership
Community & Connections
Become a Member
Divisions
People & Directories
Phytopathology News
Online Community
Diagnostic Assay Validation Network (DAVN)
The Hub: Centering Diversity in APS
News Room
Social Media Kit
Leadership & Governance
Vision & Overview
Boards & Committees
Leadership Tools
Governance
History
Committee Connections
Engagement & Outreach
Become Involved
Volunteer Opportunities
Office of International Programs (OIP)
OIP International Research Achievement
OIP Global Experience Program
OIP Global Membership Program
Library Donation Program
Silent Auction
Public Policy
Listening Sessions
PPB Opportunities
Private Sector Relations
OPSR Industry Tour
OPSR Plant Pathology Experiential Awards
Office of Public Relations & Outreach (OPRO)
OPRO Meets
August 2021
July 2021
May 2021
April 2021
March 2021
February 2021
January 2021
December 2020
July 2019
December 2021
2023 NABT Teaching Resources
Share Your Work and Research
APS Outreach Project
Awards & Giving
APS Honorary Awards
APS Foundation
Apply for Funding
Awardees
Contributors
Give to the APS Foundation
Current Established Funds
Outstanding Volunteer Award
Meetings
Calendar of Events
Annual Meetings
Plant Health 2025
Annual Meeting Archives
Plant Health 2024
Program
Sponsors & Exhibitors
Plant Health Rewind
Plant Health 2023
Program
Sponsors & Exhibitors
Networking
Meeting Photos
Recordings
Plant Health 2022
Program
Exhibitors/Sponsors
Meeting Photos
Plant Health 2021
About
Program
Sponsorship
Registration
FAQ
What's New
Plant Health 2020
About
Program
Exhibitors
Plant Health 2019
ICPP 2018
Meeting Photos
Mailing List Sign Up
Division Meetings
African Division
Caribbean Division
North Central Division
Northeastern Division
Pacific Division
Potomac Division
Southern Division
Topical Meetings
National Plant Disease Recovery System
Nematodes Impacting Soybean
2022 National Soybean Nematode Conference
Program
Sponsorship
Hotel & Travel
Health & Safety
Registration
2016 SCN Conference
The Genus
Phytophthora
– Don’t Change a Winning Concept
Publications
Journals
Phytopathology®
Plant Disease
Molecular Plant-Microbe Interactions®
Plant Health Progress
Phytobiomes
PhytoFrontiers™
APS PRESS
About
Bookstore
Online Books
Apps
Plant Disease Management Reports
Collaboration Websites
Library Subscriptions
Common Names of Plant Diseases
How to Publish with APS
Plant Health Instructor
Journal Articles
Books & Apps
PDMR Articles
Phytopathology News Articles
Images
Grow: Plant Health Exchange
Education
Disease Impacts & Management
Case Studies
Feature Articles
Studying Phytobiomes as Complex Systems: A New Framework for Learners to Scaffold Understanding
Studying Phytobiomes as Complex Systems: A New Framework for Learners to Scaffold Understanding - Appendix
Hungry Planet: Stories of Plant Diseases
Chapter One
Chapter Two
Chapter Three
Chapter Four
Chapter Five
Chapter Six
Chapter Seven
Chapter Eight
Chapter Nine
Chapter Ten
Chapter Eleven
Chapter Twelve
Chapter Thirteen
Chapter Fourteen
Lab Exercises
Topics
History
Assay Validation Glossary
Diseases and Pathogens
Feature Articles
Abiotic Disorders
Feature Articles
Introduction
Fungi, Ascomycota
Case Studies
Feature Articles
Introduction
Lab Exercises
Plant Disease Lessons
Fungi, Basidiomycota
Feature Articles
Plant Disease Lessons
Oomycetes
Introduction
Lab Exercises
Plant Disease Lessons
Disease Simulations
Fungal-like Organisms
Feature Articles
Plant Disease Lessons
Nematodes
Case Studies
Feature Articles
Introduction
Lab Exercises
Plant Disease Lessons
Parasitic Plants
Feature Articles
Introduction
Plant Disease Lessons
Prokaryotes
Case Studies
Featured Articles
Introduction
Lab Excercises
Plant Disease Lessons
Viruses
Case Studies
Feature Articles
Introduction
Lab Excercises
Plant Disease Lessons
For Educators
Teaching Articles & Notes
Introductory
Feature Articles
Plant Disease Lessons / Profiles
Lab Exercises
Case Studies
Topics
Outreach Resources
Hungry Planet: Stories of Plant Diseases
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10
Chapter 11
Chapter12
Chapter 13
Chapter14
Outreach, Extension & K12
Lesson Plans
Case Studies
Resources
PHI Author Guidelines
APS Education Center Online Teaching Portal
Illustrated Glossary
A-D
E-H
I-M
N-R
S-V
W-Z
Common Names of Plant Diseases
APS Image Database
Grow: Plant Health Exchange
Plantopia Podcast
Webinars
Workshops
Advocacy Training for All: Advanced public policy involvement for scientists across the spectrum
Basic bioinformatics and command-line tools for phytopathologists: How to handle, explore, and organize big biological data
Python and Machine Learning
Courses
Research Ethics
Seed Pathology Fundamentals
2024 Research Ethics
Seed Assays
De Bary Children's Science Book Award
Archive
Career Development
Continuing Education
Courses
Webinars
Workshops
Plantopia Podcast
Learning Collections
Careers 101
Research Forums
Professional Development Center
Building a Bright Future
Keep Your Career Moving
Launch Your Career
Careers In Plant Pathology
Related Career Sites
Job Board
Search Jobs
Post Jobs
Log In
|
Bookstore
|
Join
|
Renew
It looks like your browser does not have JavaScript enabled. Please turn on JavaScript and try again.
APS
Education
Diseases and Pathogens
Viruses
Introduction
Plant Virus Classification
Dichotomous Key Answers
Share |
DisplayTitle
Plant Virus Classification: Dichotomous Key Answers
Page Content
Answers to Study Questions:
Describe the types of genomes you observed in your plant virus sample (card set).
There are five types of plant virus genomes: ssRNA+, ssRNA-, dsRNA, dsDNA, and ssDNA.
a) Most plant viruses have positive-sense, single-stranded RNA (ssRNA+) genomes. The “sense” of a nucleic acid refers to the polarity of its molecules. Positive-sense viral RNA is the template for protein synthesis, which is a process called “translation.” Examples of ssRNA+ plant viruses are
Wheat streak mosaic virus
(WSMV) and
Lettuce mosaic virus
(LMV).
b) Fewer viruses have negative-sense, single-stranded RNA (ssRNA-) genomes. ssRNA- must be converted to a positive-sense, single-stranded RNA (ssRNA+) by an enzyme through a process called “transcription.” Once the virus RNA is in the positive sense, it can serve as a template for the synthesis of proteins. Examples of ssRNA- plant viruses are
Fig mosaic virus
(FMV) and
Raspberry leaf blotch virus
(RLBV).
c) In virus genomes with double-stranded RNA (dsRNA), one strand encodes proteins and the other strand encodes enzymes involved in RNA transcription. The presence of dsRNA in a plant cell can be associated with the replication process of an ssRNA virus or the genome of an endornavirus: a stable virus that can infect avocado and bell pepper. Viruses with this genome infect mostly fungi, but recently, viral sequences of dsRNA were isolated from plants. Examples of dsRNA plant viruses are
Bell pepper endornavirus
(BPEV),
Persea americana endornavirus
(PaEV), and
Radish yellow edge virus
(RYEV).
d) Reverse-transcribing plant viruses have double-stranded DNA (dsDNA) genomes. The production of nucleic acid involves the synthesis of DNA from RNA by an enzyme called “reverse transcriptase.” Only one family of plant viruses in this group can infect cauliflower and turnip plants. Examples of dsDNA viruses are
Banana streak virus
(BSV) and
Cauliflower mosaic virus
(CaMV).
e) Single-stranded DNA (ssDNA) plant viruses include families with small, circular genome components that contain positive or negative DNA strands. Examples of ssDNA viruses are Squash leaf curl virus (SLCV), which infects maize, tomato, spinach, and bean, and Tobacco leaf curl virus (TLCV), which infects beet, banana, and bean.
Describe the plant virus particle shapes you observed in your plant virus sample (card set).
Plant virus particles come in two basic shapes: helical and polyhedral. Helical viruses have an elongated shape and can be short, rigid rods or long, flexible filaments. Polyhedral viruses are roughly spherical. The genetic material of plant viruses may be enclosed in one particle or split between two or more particles.
Describe the disease symptoms produced by the plant viruses you observed in your plant virus sample (card set).
The most common leaf symptoms include mosaic patterns, streaks, yellowing, curling, vein banding, and lesions. The flowers of infected plants can show changes in color and shape, and the fruits can show discoloration, deformation, ringspots, and mosaic patterns.
What is a dichotomous key?
A dichotomous key is a set of characteristics of organisms that allows classifying them based on a set of hierarchal criteria. A dichotomous key is formed using a set of “yes/no” questions about the characteristics of a given set of objects. The objects are divided into groups based on the responses to the questions at the various steps of the classification process. Successive questions in the key allow the user to separate objects into smaller and smaller groups until only one object is left in a group.
What is the purpose of a dichotomous key?
The purpose of a dichotomous key is to classify organisms that present different or similar characteristics and then identify members of different groups.
Why do you think scientists classify organisms?
Scientists classify organisms because members of a group are expected to have similar traits and processes, such that studying a few individuals in a group makes it possible to describe and predict characteristics of all the group members.
Suppose you receive in your lab several small tomatoes with ringspots. Based on your dichotomous key, which virus may be causing this symptom on tomato fruit? Provide details about this virus based on the card information.
A possible cause is
Tomato bushy stunt virus
(TBSV), which has an ssRNA+ genome. The modes of transmission are through seeds, soil microorganisms, and mechanical transmission. This virus also infects pepper, potato, and eggplant.
Suppose a farmer sends you a plant with an unknown plant virus. Using an electron microscope, you see that the virus particles have a helical shape. Based on your dichotomous key, what type or types of genomes (e.g., ssRNA+, dsDNA, etc.) could the virus have?
The virus particles could be ssRNA+, ssRNA-, or dsDNA.
Return to the Lesson Plan
Healthy Plants • Healthy World
The American Phytopathological Society (APS)
3285 Northwood Circle
Ste. 100
St. Paul, MN 55121 USA
Phone +1.651.454.7250
Contact Us
©
The American Phytopathological Society.
All rights reserved.