There are so many factors that can influence how a single-origin coffee will taste when it comes to the final cup. Whether it's the altitude in which the coffee is grown, how it was processed, or how much shade it was grown in—It's pretty clear that the farming of a coffee makes just as much of an impact (if not even more) than the roasting of a single-origin coffee.
Some people get confused about the varieties of the Coffea species by labeling Arabica and Robusta as varieties. When in fact, they are actually species! Both Arabica and Robusta have sub-categories called varieties that produce unique and delicious coffee cherries. To sub-categorize even more, there are varieties within the varieties called CULTIVARS or VARIETALS.
When it comes to quality, the variety of a coffee can certainly make an impact on the taste of a single-origin coffee. There are two main varieties of Arabica that the specialty coffee industry works with, and they are called Typica and Bourbon. Both transpired out of the original Coffea plants that were taken out of Yemen and Ethiopia and grown in different parts of the world - In Ile Bourbon and Java (plus surrounding islands).
Typica coffee plants tend to be very tall, and do not yield very many coffee cherries, which usually tend to be red. However, the cherries they do produce generate a unique sweetness that cups and scores very well very consistently. These are considered to be the actual original coffee varieties that all others mutated or came from, and are also known by other names like criollo, sumatra, and arabigo.
Bourbon is a mutation of Typica, of course. It produces a higher yield than Typica and also has its own kind of distinctive sweetness. It produces a variety of colors like yellow, red, and orange.
Caturra is a mutation of bourbon, which produces high yields but almost too much for its own goods. It is very popular in Latin America thanks to the ease of picking it, but cup quality can vary.
Mundo Novo is a hybrid of Typica and Bourbon, and was discovered in Brazil. It has a high yield and it actually is noticeably disease resistant. It grows at high altitudes.
Catuai is a hybrid that was created by the Instituto Agronomico do Campinas in Brazil. It has similar qualities of Caturra since that is one of the components of the hybrid. and it comes in red and yellow.
There are countless more Arabica varieties and cultivars within them that people love to work with, but it's important that they all play a large part in the sweetness of a single-origin coffee. Hope this helps!