[jack_ (OP)]

Asa heard our recent QnA show which discussed sugar in fruit vs. cake, and wonders:

1. Is fruit being bred to be sweeter, and if so, at the cost of other nutrients? 
2. Is climate change, a hotter growing season, increasing the amount of sugar in fruit, again at the expense of other factors?

This week the ABC had a story about wine grapes being sweeter, due to the hotter summer, and less acidic.

What do you think?

[Janus]

As far as I can tell, the relationship between sugar and acidity in grapes is connected to the ripening process.  As the grape ripens, the sugar level rises and acidity drops (in part due to reduction of acid amount, but also simply because adding more sugar increases the mass of the fruit without adding more acid.)  Potassium levels also increase with ripening.
So warmer weather leads to more ripening, which increases the sugar made.   The amount of other nutrients per grape doesn't go down. It's that the relative amount of sugar goes up.

As to breeding,  In many cases, it isn't sweetness or or quality of the fruit that is being bred for, but shelf life.  They are breeding for fruit that will survive being shipped far distances and sit in a store before being purchased and used.

I'll give your an example.   Around here, we have a particular variety of strawberry..   They are very flavorful and highly sought out. The downside is that in order to achieve this high quality, the growing season is short, and they have a limited shelf life.  So they are only sold locally for a short time, and you need to use them fairly quickly after they have been picked.   They simply would not survive being shipped long distances.  You are most likely going to find them at farmer's markets (though we do have a local fast food chain that, when they are in season, offers shakes and sundaes made with them (This particular chain  uses locally produced food whenever possible) .