Preheat oven to 175C (350F) and line a 21.5cm x 8cm (8.5 inch x 3.5 inch) inch loaf tin with baking paper.
In a large bowl, sift together the plain and wholemeal flour, baking powder, baking soda, cinnamon, mixed spice and salt. Whisk to combine and set aside.
In a medium sized bowl, whisk together the sugar, oil, youghurt, eggs, extract and pumpkin puree until well combined.
Make a well in the center of the dry mixture and add the wet mixture, folding gently to just combine. Be careful not to over-mix.
Pour the mixture into the prepared loaf tin and sprinkle the crumble topping over the batter.
Bake in the preheated oven for 50-60 minutes or until a skewer comes out clean.
Let the bread sit in the tin for 15 minutes before inverting the bread onto a wire rack. Once completely cool, cut into slices.