In the following question, some parts of the sentence have been jumbled up. Rearrange the parts which are labelled as P, Q, R and S to produce a suitable sentence. Choose the most appropriate sequence.

Small scale farmers / (P) to purchasing good quality seeds besides / (Q) seeds when subjected to local agroclimatic conditions, / (R) there is always a doubt about the performance of particular, / (S) face a huge problem when it comes.

S, P, R, Q