Suppose that a farmer wishes to start a you‑pick berry farm, where customers pick their own fruit from the berry bushes. In this variety of berry, the tall, thornless, and terminal flower phenotypes are produced by the s, t, and a alleles respectively. These phenotypes are recessive to the short, thorned, and axial flower phenotypes, which are produced by the S, T, and A alleles. The farmer has two berry plants. When selfed, the first plant produces tall, thorned plants with a mixture of axial and terminal flowers. The other plant produces a mixture of tall and short plants, which are all thornless and have terminal flowers. The farmer wishes to generate a pure‑breeding line of tall, thornless plants with terminal flowers, as such plants are most convenient for berry‑picking. What are the genotypes of the farmer's two original berry plants?

The genotypes of the two original plants the farmer has are as follows:

Plant 1: ss,TT,Aa and Plant 2: Ss,tt,aa.

Explanation:

A genotype is literally the underlying makeup that will produce a result that is visible and measurable, that we know as phenotype. In this particular case, we have a farmer who wishes to establish his farm with a specific type of plant: one that is tall, thornless, and has terminal flowers because they are the best for berry-picking, and that is the business he wishes to establish.

In order to be able to obtain this type of plant, he needs to first count with a starting point, the parent plants from which he will be able to produce the line he wants to establish. But to do that he needs to first know the genetic makeup with which, when he crosses the plants, he will then obtain the phenotypical results he seeks.

The question itself tells us the types of alleles (which are, in simple terms, the holders of the genetic information), that produce the phenotypical characteristics of the plants the farmer has.  So we know that there is one type of bush that is tall, thornless and has terminal flowers, and its alleles are s, t and a. The other bush has short, thorned and axial characteristics, and therefore its alleles are: S, T and A.

When the question then gives us the information about the resulting plants when the originals are selfed, and their characteristics, we are able to tell the genetic makeup, or genotype, of the original two plants the farmer has because we can combine the alleles mentioned given the characteristics (phenotypes) and thus obtain the two parent plants.  

The genotypes of the two original plants the farmer has are as follows:

Plant 1: ss,TT,Aa and Plant 2: Ss,tt,aa.

Explanation:

Hope this helps