Difference Between Biotrophic and Necrotrophic Fungi

The key difference between biotrophic and necrotrophic fungi is that biotrophic fungi derive nutrients from living plant cells, maintaining the viability of host cells, while necrotrophic fungi kill their host tissues and then derive nutrients from the dead tissues.

There are several types of plant fungal pathogens, such as biotrophic, necrotrophic and hemibiotrophic, etc., based on their lifestyle and interaction with the host. Biotrophic fungi obtain nutrients from living plant cells.  They do not kill host tissues. In contrast, necrotrophic fungi rapidly kill host tissues and derive nutrients from the dead cells. Biotrophic fungi have a narrow host range since they are specialized pathogens. Necrotrophic fungi are opportunistic or unspecialized pathogens. Hence, they have a wide host range.

CONTENTS

1. Overview and Key Difference
2. What are Biotrophic Fungi
3. What is Necrotrophic Fungi
4. Similarities Between Biotrophic and Necrotrophic Fungi
5. Side by Side Comparison – Biotrophic vs Necrotrophic Fungi in Tabular Form
6. Summary

What are Biotrophic Fungi?

Biotrophic fungi are a specialized group of plant pathogenic fungi. They require living plant tissues to obtain nutrients. They do not kill host cells; instead, they maintain the viability of host cells, causing little damage. Hence, these biotrophic fungi establish a long term feeding relationship with plant cells rather than killing the cells. Fungal mycelia grow between plant cells and produce nutrient-absorbing structures known as haustoria.

Rust fungi are one of the best examples of biotrophic fungi. Powdery mildew fungi are another example of biotrophic fungi.  Biotrophic fungi reduce the competitive ability of the host plant. Moreover, they can cause serious economic losses to crop plants. Powdery mildew, maize smut, tomato leaf mould, black stem rust of cereals and potato late blight are several diseases caused by biotrophic fungi.

What are Necrotrophic Fungi?

Necrotrophic fungi are a group of opportunistic or unspecialized pathogenic fungi. They invade and kill host cells, especially plant cells, rapidly. Then they derive nutrients from the dead tissues saprotrophically. Generally, necrotrophic fungi do not produce haustoria or appressoria. There is a wide host range for necrotrophic fungi. Generally, they attack weak, young and damaged plants. They enter plant cells via wounds and damaged tissues. Then they secrete copious cell-wall-degrading (lytic) enzymes and toxins to kill cells.

Pythium and Fusarium are two examples of necrotrophic fungi. Grey mould, corn leaf blight, damping off in seedlings, Dutch elm disease, vascular wilt and soft rot are several diseases caused by necrotrophic fungi.

What are the Similarities Between Biotrophic and Necrotrophic Fungi?

• Biotrophic and necrotrophic fungi are two types of plant pathogenic fungi.
• They derive nutrients from plant cells.
• Moreover, they grow intercellularly among the host cells.
• They cause economic losses of crops.

What is the Difference Between Biotrophic and Necrotrophic Fungi?

Biotrophic fungi obtain nutrients from living plant cells, while necrotrophic fungi kill plant cells and obtain nutrients from dead tissues. So, this is the key difference between biotrophic and necrotrophic fungi. Besides, biotrophic fungi usually do not kill host cells. They cause little damage. But, necrotrophic fungi secrete cell wall degrading enzymes and toxins to kill host cells rapidly. Thus, this is another significant difference between biotrophic and necrotrophic fungi.

The below infographic lists more differences between biotrophic and necrotrophic fungi in tabular form.

Summary – Biotrophic vs Necrotrophic Fungi

Biotrophic fungi do not kill plant host cells. They grow between cells and obtain nutrients from the living cells. In contrast, necrotrophic fungi rapidly kill plant host cells and then live on dead tissues obtaining nutrients. Thus, this is the key difference between biotrophic and necrotrophic fungi. Biotrophic fungi produce haustoria in order to absorb nutrients, while necrotrophic fungi do not produce haustoria. Moreover, biotrophic fungi are specialized pathogens, while necrotrophic fungi are opportunistic or unspecialized pathogens.

Reference:

1. David Moore, Geoffrey D. Robson and Anthony P.J. Trinci. “21st Century Guidebook to Fungi, Second Edition, by David Moore, Geoffrey D. Robson and Anthony P. J. Trinci.” 14.10 Necrotrophic and Biotrophic Pathogens of Plants, 1 July 2019, Available here.
2. “Biotrophic Plant Pathogens,” The Microbial World, Available here.

Image Courtesy:

1. “Rust fungus – Flickr – gailhampshire” By gailhampshire from Cradley, Malvern, U.K – Rust fungus (CC BY 2.0) via Commons Wikimedia
2. “Grey Slime Mould – Flickr – treegrow (1)” By Katja Schulz from Washington, D. C., USA – Grey Slime Mould (CC BY 2.0) via Commons Wikimedia