By L Gene Albrigo
Citrus is one of the most important exported fruit crops. Large plantings in countries bordering latitudes 20 south and north and in-between provide fresh and processed citrus for the more populated northern European and American countries as well as other large populations around the world. Citrus has also been a cultivated crop in southeast Asia for thousands of years. Its genetics are unique in that stable hybrids naturally propagated through polyembryony have been recognized as species. New molecular techniques have clearly elucidated the true genetic background of citrus.