Agronomy and Horticulture Department



Breeding for Resistance in California Strawberry to Verticillium dahliae

Date of this Version


Document Type



Plant and Soil Sciences eLibrary (PASSeL) Lesson


Copyright © 2014 Zachary Christman and Deana M. Namuth. Used by permission.

This project was supported in part by the National Research Initiative Competitive Grants CAP project 2011-68002-30029 from the USDA National Institute of Food and Agriculture, administered by the University of California-Davis and by the National Science Foundation (NSF), Division of Undergraduate Education, National SMETE Digital Library Program, Award #0938034, administered by the University of Nebraska. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the USDA or NSF.

A special thank you to the University of California, Berkeley and University of California, Davis for the use of their research in developing this e-library lesson. Development of this educational material was supported in part by the University of Nebraska Institute of Agriculture and Natural Resources. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of UNL.



This e-library lesson will focus on breeding resistant strawberries to the fungus Verticillium dahliae, common name Verticillium wilt. This is a serious fungal disease that can result in a loss of 50% or more of a strawberry harvest when grown in infested soil. This lesson is written for undergraduate and graduate students who are currently studying plant pathology or the management of crop disease. The main goal is to provide an example of how a cultivar can be made more resistant to a plant pathogen with the use of plant breeding methods.

Background Information

Since 1930 the University of California, Davis, has been developing strawberry cultivars that are adapted to the agricultural industry and regional farms. Developing cultivars that require fewer inputs are of significant economic importance in agronomy. Developing a crop resistant to a disease is beneficial for horticulturists since less labor and chemicals are needed for a high yield.

In commercial strawberry cultivars, complete resistance to V. dahlia is extremely rare. The majority of Californian strawberry cultivars are highly susceptible to it. Over the last 18 years of plant breeding for strawberry cultivars with a high degree of resistance and horticultural traits, strawberry cultivars with at least moderate resistance grew to 53.8% of the strawberry germplasm being measured in the study. Each plant was rated from 1 to 5 based on symptoms of V. dahliae in comparison to control plants over the length of the study.

  • The lowest ranking was 1, meaning severe stunting or death
  • A ranking of 3 indicated moderate damage and signs of tolerance
  • The highest ranking was 5, indicating no disease symptoms


After completing this lesson you should be able to:

  • Explain the importance of strawberry resistance to Verticillium dahliae
  • Examine the process for family selection and direct genotypic evaluation for resistance
  • Describe how the plants were graded for stages of Verticillium dahliae infection