China: Scientists Sequence Orange Genome

Chinese scientists have sequenced the genome of the sweet orange (Citrus sinensis), marking the first time that a Chinese research team has independently determined the genome sequence of a fruit crop.

The data, which is expected to help scientists understand the complex genetic make-up of the crop in order to improve its quality and yield, was the result of a year’s effort by a team of horticulture, genomics, and bioinformatics experts at the Central China Agricultural University in Wuhan, the capital of Hubei province.

Breeds of citrus are among the most widely grown fruit crops in the world. The sweet orange, which originated in China, is the most commonly grown fruit tree in the world, and its production accounts for about 60 percent of total citrus production.

The sweet orange, mostly poly-embryonic, is highly heterozygous, which means it has dissimilar pairs of genes for any hereditary characteristic, and is plagued by sterility. Therefore, determining its genetic make-up may provide the basis for genetic breeding, according to Xu Qiang, an expert with Central China Agricultural University.

Of the more than 80 types of citrus species grown in China, 40 percent are not native to China, and half of the country’s fruit production is generated from foreign breeds, said Deng Xiuxin, an academician with the Chinese Academy of Engineering and leader of the research team.

Deng compared sequencing the genome of the sweet orange to opening the "black box" of the crop’s life activities, a move that may help to improve the fruit’s traits, including color, taste, yield, and disease resistance.