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Chinese scientists have sequenced the genome of the sweet orange (Citrus sinensis), the first time a Chinese research team has independently determined the genome sequence of a fruit. The achievement opens the door to better quality and higher crop yields, and provides a scientific basis for developing modified genetic breeds that do not have fatal viruses. The Chinese research team, led by professor Deng Xiuxin, a member of the Chinese Academy of Engineering, and professor Ruan Yijun from Huazhong Agricultural University - along with horticultural, gene and bioinformatic scientists - assembled and annotated the sweet orange genome for a high quality genome. Citrus fruits are among the most important and widely grown fruit crops in the world, with global production and total area ranking first among all fruit crops. Sweet oranges account for about 60 percent of citrus production, both as a fresh fruit and processed juice. Citrus is susceptible to a large number of biotic diseases, especially citrus yellow mosaic, which is transmitted by the Asian citrus psyllid, a sap-sucking bug also found in the Middle East and America. It has not been a good year for sweet orange farmers in Guangdong province, where the citrus yellow mosaic virus has infected many trees. Currently, there is no effective way of dealing with the virus and the only way to stop the virus spreading is to root out the trees and burn them. Worse, the infected land cannot be used for sweet orange production for years afterward. It is reported that more than 20 percent of sweet orange trees were infected this year in Guangdong, one of the country's major citrus growing areas. Deng compares sequencing the genome of the sweet orange to opening the fruit crop's "black box", an achievement that could improve the fruit's color, taste, yield and disease resistance. Oranges are mostly polyembryonic, meaning two or more embryos develop from a single fertilized egg. These characteristics hinder development, while a complete genome sequence could provide a valuable molecular framework for breeding and improvement. |
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