The fruit and plant of the avocardo are toxic to dogs, so no do not feed that to your dog. :-)
If you remove the seeds many fruit and veg can be given to our dogs though, some that come to mind below:
Apple, apricot, banana, blueberries, cantaloupe, mango, oranges, pear, pineapple, raspberries, strawberries, watermelon,
Asparagus, broccoli, cabbage, carrots, cauliflower, celery, cucumber, green beans, sweet potato, spinach, lettuce (Boiling veg helps digestion also)
Also never give grapes and raisins, avoid completley, very dangerous, will cause damage to the kidneys. Lemons, limes and grapefruit can cause stomach upsets and onions, garlic and mushrooms should never been given to a dog.
Oh gosh, don't want to cause panic, it may well be an old wives tale with them being part of the onion family? I can only go on what I have been brought up with which is that garlic like the onion destroys the red blood cells, making them burst and thus have always avoided it. I think I will do some checking...........