Bananas are not high in sucrose although bananas do contain some sucrose but it's not the dominant sugar in bananas.
Bananas also contain glucose and fructose, and the total sugar content of a banana is a mix of sucrose, glucose and fructose, with sucrose making up a portion of the total of the sugars.
And as a banana ripens, the starch content in the banana also decreases and the sugar content including the sucrose in the banana increases.
Sucrose is also known as table sugar and is a disaccharide, which means that sucrose is made up of 2 simpler sugar molecules and it can also be naturally occurring as a carbohydrate that can be found in many fruits, plants and vegetables.
Sucrose is also widely used as a sweetener in foods and beverages and is also produced commercially from sugarcane and sugar beets.
Sucrose is made from beets or sugarcane which is different from High Fructose Corn Syrup.
If it's the regular sucrose then it's not made from corn and is made from the sugarcane or beets.
But for the high fructose corn syrup the high fructose corn syrup is made from corn.
Sucrose and High Fructose corn syrup are sometimes confused with each other by some people but they are different and made from different things.
But since starch itself is a simple sugar, a chain of glucose molecules joined together, once it becomes broken down into individual glucose molecules, it's then actually corn syrup, which is essentially 100% glucose.
So if you have sucrose it's made of beets or sugarcane but for high fructose corn syrup it's made from corn.