Given an example of a plant where the F2 progeny of a monohybrid cross has same genotypic and phenotypic ratios.

Snapdragon/Antirrhinum majus Four O' clock plants / Mirabilis jalapa.

Detailed answer : 

In monohybrid cross normally the phenotypic ratio is 3 : 1 due dominant-recessive relationship and genotypic ratio is 1 :2 :1. But in case of some plants like Snapdragon and four O' clock plants  there is incomplete dominance as a result of which there appear some intermediate phenotypes vesicles the parental types in the ratio of 1 :2: 1 which is a genotypic ratio also. Therefore, in these plants the phenotypic and genotypic ratio is the same.