Cause of watermelon rind rotting (at room temperature) I bought a large seedless watermelon 2 days ago, and I made sure to check for the following:


Yellow underbelly
Hollow sound
Solid rind


When I got home I left on the kitchen table. The room temperature was around 25-27 degrees C. Today, I touched the rind and it felt soft! I cut it open and I saw that the white pith had rotted. 

Can anyone explain what the possible cause of this is? 

(I've left watermelon out on the dining table for days at room temperature before, and nothing like this has ever happened. I should also mention that:


The watermelon was whole and unblemished. 
There were no fruits around it and it wasn't in a bag, so the ethylene explanation is out.
Without forensics it's hard to tell exactly what happened.
However, one possible explanation is sunlight. If the watermelon was in the sun at all, even just a little part of it, that tends to accelerate the growth of all sorts of things.

Another possibility is that it was just past its date. There isn't really a way to tell if this is near or not without chemical analysis.

In watermelon country (I live near an ancient greek watermelon port) watermelon is generally refrigerated. This is partially because we find it tastier when it's cold, and partially because room temperature easily goes above 30, and even above 34-5 on certain days.