How to customize the content of a legend of a dotplot with ggplot2

i am using this table:

fruit   value   feature Ratio
tomato  1.79614067223751    length  0.00983606557377
zucchini    3.03886853214095    size    0.034188034188034
tomato  1.64545172419968    size    0.013114754098361
potato  4.25443807208955    size    0.008383233532934
zucchini    5   colour  0.051282051282051
potato  1.46068422675856    magic   0.004790419161677
potato  5   flavour 0.011377245508982
tomato  4.86348870541553    flavour 0.026229508196721
zucchini    2.89808116631958    flavour 0.034188034188034

to produce this dotplot

Dotplot <- read.delim("test.txt", header = TRUE)

ggplot(Dotplot,aes(factor(fruit),feature)) + 
        geom_point(aes(colour=value,size=Ratio)) + 
        scale_colour_gradient(low="red", high="blue") + 
        scale_size(range=c(1,10)) + theme_bw() + 
        theme(axis.text=element_text(size=10), 
              axis.title=element_text(size=10,face="bold")) + 
        theme(axis.text.x = element_text(size = 12, angle = 90))

what i want is to customize the "Ratio" legend and double the quantity of dots to display even values for very small dots. Is that possible?

thanks in advance