The key difference between vertical and horizontal resistance is that vertical resistance is the resistance of plants that controlled by a single gene, while horizontal resistance is the resistance of plants that is controlled by many genes.
Plants’ resistance mechanisms against pathogens are often chemical in nature. These resistance mechanisms may be naturally occurring or induced. Naturally occurring resistance mechanisms are present in the host plant tissues prior to their contact with pathogens. But induced resistance mechanisms occur only after such contact with the pathogen. The plant pathologist “Vander Plank” introduced the concept of vertical and horizontal resistance in 1963. They are two types of disease resistance mechanisms of plants against pathogens.
CONTENTS
1. Overview and Key Difference
2. What is Vertical Resistance
3. What is Horizontal Resistance
4. Similarities Between Vertical and Horizontal Resistance
5. Side by Side Comparison – Vertical vs Horizontal Resistance in Tabular Form
6. Summary
What is Vertical Resistance?
Vertical resistance is the resistance of plants against pathogens that is controlled by a single gene. The term vertical resistance is commonly used in plant selection. It was first used by J.E. Vander Plank in 1963 to describe single-gene resistance. Raoul A. Robinson further redefined the term by emphasizing the fact that in vertical resistance, there are single genes for resistance in the host plant, as well as single genes in the pathogen for pathogen ability. Thus, this phenomenon is also known as the gene for gene relationship or model.
Figure 01: Vertical Resistance
According to J.E. Vander Plank, vertical resistance is a kind of resistance in plant varieties that are effective against some races of the pathogen and not against others. Therefore, vertical resistance is highly specific. Moreover, such resistance differentiates clearly between the races of the pathogen as it is effective against some races and ineffective against others. In vertical resistance, pathotype specificity means the host is carrying a gene for vertical resistance that is only attacked by pathotypes that carry a virulent gene toward that resistance gene. However, vertical resistance in plants is unstable and less durable.
What is Horizontal Resistance?
Horizontal resistance is the resistance of plants against pathogens that is controlled by many genes. It is sometimes called generalized resistance. This term also was first used by J.E. Vander Plank in 1963. J.E.
Raoul A. Robinson further redefined the definition of horizontal resistance by emphasizing the fact that, unlike vertical resistance and vertical pathogen ability, horizontal resistance and horizontal pathogen ability are entirely independent of each other. Horizontal resistance is sometimes called partial, non-race specific, quantitative or polygenic resistance in plants. Furthermore, in horizontal resistance, the reproduction rate of the pathogen is never zero, but it is less than 1 according to statistical analysis. Horizontal resistance is stable and durable.
What are the Similarities Between Vertical and Horizontal Resistance?
- Both are types of disease resistance in plants.
- They are very important for plant immunity against pathogens.
- They emphasize the relationship between plant and pathogen.
- Both are under genetic control.
What is the Difference Between Vertical and Horizontal Resistance?
Vertical resistance is the resistance of plants against pathogens that is controlled by a single gene. Horizontal resistance is the resistance of plants against pathogens that is controlled by many genes. So, this is the key difference between vertical and horizontal resistance. Moreover, another difference between vertical and horizontal resistance is that the vertical resistance in plants is unstable and less durable. In contrast, horizontal resistance in plants is stable and highly durable. Most importantly, vertical resistance is race-specific while horizontal resistance is race non-specific.
The below infographic lists the differences between vertical and horizontal resistance in tabular form.
Summary – Vertical vs Horizontal Resistance
Disease resistance is defined as the ability to prevent or reduce the presence of diseases in the host. It arises from genetic or environmental factors. Disease tolerance is different from plants to plants as it is the ability of a host to limit the impact of disease on host health. The concept of disease resistance is categorized into two types: vertical and horizontal resistance. Vertical resistance is the resistance of plants that controlled by a single gene, while horizontal resistance is the resistance of plants that is controlled by many genes. Thus, this is the summary of the difference between vertical and horizontal resistance.
Reference:
1. “Vertical Resistance.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., Available here.
2. “Horizontal Resistance.” An Overview | ScienceDirect Topics, Available here.
Image Courtesy:
1. “Plant Immunity Diagram” By Clee 08 – Own work (CC BY-SA 4.0) via Commons Wikimedia