This problem involves a dihybrid cross. The parent generation has genotypes \( RRyy \) (round, green) and \( rryy \) (wrinkled, yellow). The \( F_1 \) generation is \( RrYy \) (round, yellow).
The \( F_2 \) generation phenotypic ratio is:
Therefore, to observe at least one plant with each phenotype, you would need a minimum of 16 plants. The question asks for the minimum number to observe wrinkled green seeds. Therefore, at a minimum, you would need 1 plant.