Question

When two lines possessing two different alleles of resistance (say, DM1 and DM2) for a particular disease are crossed, the two alleles interact to induce disease resistance response in the hybrid without pathogen attack and produce necrotic lesions. Such a phenomenon is referred to as-

• A. Hypersensitive reaction
• B. Hyper-insensitive reaction
• C. Induced immune response
• D. Autoimmune response

Hint:

When different resistance alleles interact to trigger cell death and defense pathways without a pathogen present, it is a plant autoimmune response, often called hybrid necrosis.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Plant immunity relies on complex networks of immune receptors, such as nucleotide-binding leucine-rich repeat (NLR) proteins, to detect specific pathogen molecules.
Inappropriate activation of these pathways can lead to tissue damage in the absence of infection.

Step 2: Detailed Explanation:
In some plant crosses, the combining of distinct immune receptor alleles or different disease resistance alleles (such as \(DM1\) and \(DM2\)) causes a genetic mismatch in the \(F_1\) hybrid.
This mismatch triggers an inappropriate, constitutive activation of the plant's defense pathways in the absence of any pathogen attack.
This systemic defense activation leads to spontaneous cell death, resulting in necrotic lesions and stunted growth.
This genetic incompatibility and inappropriate immune activation is a form of hybrid necrosis, which acts as a plant autoimmune response.
The plant's immune system mistakenly attacks its own healthy tissues, mimicking a hypersensitive response without a pathogen stimulus.
While a hypersensitive reaction (A) is a localized cell-death response triggered by an actual pathogen, the spontaneous activation described in the question represents an autoimmune response.

Step 3: Final Answer:
This genetic phenomenon is referred to as an autoimmune response, corresponding to option (D).