Hello, I have purchased a moro orange tree. It was a hard to find for me. So, even though it was on dwarf rootstock, I purchased it. It was bought and planted in the spring of 2010. Since it being on a dwarf rootstock, it is slow in growth. So I was thinking of making a raised bed of some sort to pour in more dirt around the base to fill above the point where the grafting was done. Would this make the plant grow any faster if upper portion took root? I might of read somewhere that that this might cause the tree to be more disease prone. Would this be true?

It is usual to keep the graft union well clear of the soil, to prevent phytophora etc from attacking that area.If you went ahead and rooted the scion your plant would eventually be on equivalent to sweet orange stock.
Sweet orange is used as a rootstock, but most other stocks are probably better choices, unless you have light sandy loam soil, can control moisture, and have no root pathogens. How about inarching the moro trunk to a vigorous stock, or simply use your moro as budwood to produce a more suitable tree to plant out, and keep the original as a pot specimen ?

That sounds safer than what I was thinking of. I might try that inarching. Thanks.