Apple was originated in Central Asia.It is one of most widely planted fruit tree .China is the number one producer of apple .
With proper care apple tree with low chill requirement can thrive in low desert of southwest.
         There are sevral varieties of apple .The details of  3 varieties which can be grown in Arizona is given below .                                                              
Anna Apple
Anna apple have green yellowish color with red blush skin .These  apples are crispy and have creamy white flesh .Its flavor is sweet but slightly tart.It is partial self fruiting but can be pollinated by Dorsett Golden or Ein Shemer .It Ripes in June in phoenix. it needs only 200 to 300 chill hours. This is a great choice for those in mild winter locations.
Dorsett Golden
Dorsett Golden are outstanding, medium to large size are firm and very flavorful sweet apples for mild winter areas. They ripe in late June/July and are good pollenizers for Anna. They require 150 chill hours and are self-fruitful.

Ein Shemer Apple

The Ein Shemer Apple Trees need very low chilling. It originated from Israel. Ein Shemer Apple are large, golden and delicious with a crispy tart flavor. The Ein Shemer Apple tree is  self-fertile  and requires 350 chill hours.

Photo shown here are  Anna, Dorsett Golden and Ein Shemer. They are planted 2 feet apart from each other and are about 2 years old . They are on the south side of my house and get shade in late afternoon. As seen all the trees are loaded with fruits.
Plant care
Apple trees can thrive and produce good crops in lower desert of southwest with proper care.

 I irrigate them after every 7-14 days during growing season and after every 4 to 6 weeks during the winter.

We have 3 to 5 inch thick layer of partially compost mulch around the tree drip line  which provides all nutrient to the plant for healthy growth.
Paint the trunk of young tree with water soluble white paint mixed with 50/50 water to prevent sun burn.

Medicinal Properties
There is a old saying
To eat an apple going to bed ,
Will make the doctor beg his bread.