Citrus Breeding and Genetic Improvement Programme in China

Citrus breeding and genetic improvement in China began in 1960s, but was reduced in the 1980s-1990s for many reasons. Recently, this program was re-organized again. In 2003, the government invested one citrus breeding centre in Huazhong Agricultural University and one citrus improvement centre in Citrus Research Institute of CARS (now the Southwest University). The breeding objectives include extending harvest seasons, and the seedlessness of seedy varieties. Since 2000, a total of 15 new cultivars were released by provincial governments; these cultivars came from bud-sport or from chance seedling selection. These include 3 navel oranges, 4 common sweet oranges, 7 loose skin mandarins, and 1 pummelo. These cultivars have elite characters such as prolific yields, good fruit uniformity, high sugar content, and seedlessness. A program aiming at seedless breeding began in the author's laboratory via the combination of conventional breeding and biotechnology. About 5 bud mutants with special traits such as precocity, early maturity and purple color of the fruit skin etc. were collected in the past 5 years from a nation-wide search. By using the allotetraploids from somatic hybridization as the pollen parents to cross with seedy varieties such as Shatian pummelo, a total of more than 300 triploid plants were obtained. Protoplast fusion with Satsuma mandarin as the CMS donor has led to the regeneration of 8 diploid cybrids of seedy varieties; analysis of the cytoplasm genetic constitution verified their harbouring the cytoplasm from Satsuma mandarin.