Question

Consider the following events.
1. Germ tube formation
2. Appressorium formation
3. Penetration
4. Haustoria formation.
The correct sequence in which these events take place during plant infection is?

• A. $2,1,4,3$
• B. $2,3,1,4$
• C. $1,2,3,4$
• D. $1,2,4,3$

Answer 1

Answer: (C)

$1,2,3,4$

The correct answer is C.

Some fungal pathogens release spores into the air and the spores are then spread with the aid of air currents.

Wound sites and natural plant openings, such as stomata and hydathodes, facilitate the entrance of some plant pathogens, others have evolved unique mechanisms for direct penetration. Fungi and nematodes are able to actively penetrate host tissues and cells if environmental conditions, such as moisture and temperature, are favorable for the penetration process.

A germ tube is an outgrowth produced by spores of spore-releasing fungi during germination. Viruses, bacteria, and phytoplasmas are not able to actively penetrate or enter plant host tissues. Therefore they must rely on other methods to infect plant tissues and cells. Associations with insect vectors have been established by these pathogens to aid inoculation and dispersal.

The development of the haustorium is the final step of an infection pathway in which the plant host plays a major role. In the case of rust fungi, infection typically begins with the germination of a spore on the leaf surface, followed by the development of an appressorium.