In certified class seed production of a three-line system, —–line is used in the border row. (JFR Plant Science 2018)

✏Three-Line System: This system is commonly used for hybrid seed production in crops like rice, maize, and sunflower. It involves three distinct lines:
-A-line: The female parent, which is male-sterile (cannot produce viable pollen).
-B-line: The maintainer line, used to pollinate the A-line and maintain its male sterility.
-R-line: The restorer line, used to pollinate the A-line to produce hybrid seed.
-Certified Seed Production: This stage focuses on producing hybrid seed for commercial use. The A-line is planted in the main field, and the R-line is used in the border rows.

✏Why R-line in Border Rows:
-Pollen Source: The R-line provides abundant pollen to ensure adequate pollination of the A-line.
-Genetic Purity: Using the R-line in border rows helps maintain the genetic purity of the hybrid seed by minimizing the chances of pollen contamination from other sources.
-Uniformity: This ensures that the resulting hybrid plants will have the desired traits and uniformity.
-Seed Production Ratio: A common planting ratio for certified seed production is 4:2 (A-line: R-line), with 4 rows of the R-line planted as the border.

📌 Other Options Explanations:
-A-line: The male-sterile line, planted in the main field for hybrid seed production.
-B-line: Used to maintain the A-line's male sterility, not for producing hybrid seed.