Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): The diploid wild species of potato are self-incompatible due to gametophytic self-incompatibility system.
Reason (R): A dominant self-incompatibility inhibitor gene (Sli) has been identified in the wild species of Solanum chacoense.
In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Self-incompatibility (SI) prevents self-fertilization. In potato, it's often Gametophytic SI (GSI). The Sli gene is an inhibitor of this GSI system. Understanding genes that modify or break SI (like Sli) helps scientists better understand the SI mechanism itself.

Answer 1

The Correct Option is A

Assertion (A): The diploid wild species of potato are self-incompatible due to gametophytic self-incompatibility system. This statement is true. Many wild diploid relatives of the cultivated potato (Solanum species) possess a gametophytic self-incompatibility (GSI) system. In GSI, if the S-allele (gene variant for self-incompatibility) in the pollen matches one of the S-alleles in the pistil (female part of the flower), pollen tube growth is inhibited, preventing self-fertilization. This promotes outcrossing. Reason (R): A dominant self-incompatibility inhibitor gene (Sli) has been identified in the wild species of Solanum chacoense. This statement is also true. The Sli (S-locus inhibitor) gene has been found in Solanum chacoense, a wild potato species. This dominant gene can suppress the GSI system, allowing self-fertilization even in plants that would otherwise be self-incompatible. Is (R) the correct explanation of (A)? The discovery and study of the Sli gene (Reason R) significantly contribute to our understanding of the gametophytic self-incompatibility system mentioned in Assertion (A). By identifying a specific gene (Sli) that can "switch off" or inhibit the self-incompatibility mechanism, scientists gain deeper insights into how the GSI system functions at a molecular level. For example, knowing how Sli inhibits S-RNases (key components of GSI in potato) helps elucidate the S-RNase mechanism itself. Thus, understanding how SI is broken (by Sli) helps to explain the workings of SI itself. Therefore, (R) provides a genetic context and mechanism that helps explain and validate the complex genetic system of self-incompatibility described in (A). Both statements are true, and the identification and understanding of the Sli gene's function help explain the genetic basis and regulation of the self-incompatibility system in these potato species. Both (A) and (R) are true and (R) is the correct explanation of (A).