Step 1: Check each disease symptom.
\[
\boxed{
\begin{aligned}
&\text{Mosaic} &&\rightarrow \text{Tobacco mosaic disease} &&\text{Correct}
&\text{Vein clearing} &&\rightarrow \text{Bhendi vein clearing} &&\text{Correct}
&\text{Breaking of flowers} &&\rightarrow \text{Tulip mosaic disease} &&\text{Correct}
\end{aligned}
}
\]
Step 2: Identify the incorrect pair.
Swollen shoot of potato is not an example of malformation.
Hence, the pair
\[
\boxed{\text{Malformation} \rightarrow \text{Swollen shoot of potato}}
\]
is incorrect.
Step 3: Choose the correct option.
Therefore, the correct option is
\[
\boxed{(C).}
\]