What is agricultural transformation and rural development?

Agricultural transformation is the process by which individual farms shift from highly diversified, subsistence-oriented production towards more specialized production oriented towards the market or other systems of exchange (e.g., long-term contracts). The process involves a greater reliance on input and output delivery systems and increased integration of agriculture with other sectors of the domestic and international economies. Agricultural transformation is a necessary part of the broader process of structural transformation, in which an increasing proportion of economic output and employment are generated by sectors other than agriculture.

Thus is process is one way of attaining rural development since majority rural areas are engaged in agriculture. that's the linkage of the two. Rural development can be attempted through other processes like, small-scale enterprise development, education..although these can be part of agricultural transformation too.

Look at the journal of agrarian change, you will find additional reading material that can clarify this further