What is the exact reason to reject this photo?

Hi oleschwander

The image is a bit small, hence not easily inspected. Usually you receive a mail with the reason for rejection. That is usually helpful to include in your question. However looking at your thumbnail, it would appear to be out of focus. It is not sharp enough. Additionally the top tomato appears to be grainy. In addition you could lighten the shadows a bit so that more details are made visible in the dark areas.

I hope this helps

Regards

JG