I would like to know what fruit trees perform well in the southern U.S. Mississippi, Alabama, etc.
Pears, apples, peaches, plums, figs as a general rule but in most of those you need to be careful in your selection of cultivars for the southern climate. For instance most european pears suffer terribly from fireblight in the humid south. Many apples require longer chilling hours then the south provides. Plums can be problematic, most europeans fail and the asians which do best can have disease issues as do almost all peaches if a stringent spray program is not maintained. Fortunately figs are almost completely trouble free in the south.
Coastal AL and MS can grow the hardier citrus and many exotics do well such as pomegranites, paw paws, persimmons.
jujube's will do great with no care. some pears will need almost no care; trick is to find those that are fireblight resistant in your area, maybe by checking with reputable local nursery's.
Jujube's are a good return for little effort. However, the Li and Lang varieties (most common) are not in my humble as tasty as an average apple (I have Lang and use almost exclusively for cooking). Google Roger Meyer for some better varieties you can mail order.
An extension service in the Houston area is selling the following apple varieties at its next meeting, so I think they should work well most other places in the South. I'm putting the chill hours in parens: Anna (200), Beverly Hills (300), Dorsett Gold (200), Ein Shemer (100), Gordon (400), Pettingil (100), White Winter Pearmain (400), Yellow Bellflower (400).
I live far from the south, the Gulf series plums were bred in Florida and the AU series plums in Alabama University.
Here is a link that might be useful: Plums for the South
Some of the hardier citrus: satsumas, calamondin, kumquat, yuzu will do well if close to the coast. Most of those are sour citrus, though some of 'em (yuzu, calamondins) are dynamite things to cook with. Yuzu is a bit more rugged and hardy than other citrus - they are seriously thorny, but the fruit really earns its' hype.
Likewise feijoas, which are generally hardy to zone 8. They are fairly hardy, but can be sensitive to (a) extreme cold, (b) heat over about 95, and (c) strong wind. Mine got very sluggish during the hottest part of summer, but there was a good surge of autumn growth. They are very resilient, and aren't very picky about soil. Their only drawbacks: they can be fruit fly magnets (very, very pest-free otherwise), and getting fruit set is very challenging, and even moreso in places with humid summers.
Check out justfruitsandexotics.com for a large selection.
I like their Asian Pears and Persimmons.
They're located near Tallahassee and specialize in Deep South Fruit Trees.
I live near Montgomery AL and would HIGHLY recommend you contact your local county extension office and ask them. One thing I've learned since getting into the fruit growing business about 5 years ago is that fruiting plants that do well as close as 100 miles away, may not do well where you live, depending on your location and growing environment. It will only take you a small amount of time to meet with them, but will save you many hours of frustration and dollars down the road. Also, make sure you get a soil test done where you plan to plant. Again, the cost savings down the road from having healthy, vigorous plants growing in the appropriate soil structure will definitely out weigh the $7-8 is costs to get your soil analyzed.
Hope this helps,