Maize is one of the major cereals that are important for feedstuff, industrial feedstock and human foods. Specialty maize, such as sweet corns and waxy corns, has been welcomed by consumers for a long time. Maize breeding is often challenged by breeding efficiency due to lack of natural variation. This process, however, can be accelerated by application of new technologies such as newly emerged genome editing technology. However, the breeding of specialty maize has largely relied on naturally occurred mutants which often confer genetically linked undesired traits. Recently, Maize Molecular Breeding Research Team from Institute of Crop Science, Chinese Academy of Agricultural Sciences (ICS-CAAS), showed that multiplex CRISPR/Cas9 targeting on two genes within the same synthetic pathway for starch could both overcome the limitation to acquire gene mutations and contribute to an effective breeding scheme for specialty types of sweet corn, waxy corn and sweet-waxy- compound corn.Two genes, SHRUNKEN2 and WAXY  were edited simultaneously with high efficiency. Double recessive alleles were readily obtained by crossing single mutants, resulting in double flavored “transgene-free” SWC corns. This gene editing based approach also provides feasible ways for modifying many other loci, such as Su1 , Su2 , Bt1 , and Bt2 , that could also be integrated into the scheme to produce additional specialty corns.

This result entitled “Supersweet and waxy: meeting the diverse demands for specialty maize by genome editing” was published on PLANT BIOTECHNOLOGY JOURNAL . This work was supported by grants from Beijing Municipal Science and Technology (Major Program D171100007717001), the China National Major Research and Development Program (2016YFD0101803) and the Agricultural Science and Technology Innovation Program (ASTIP),CAAS.

By Xie Chuanxiao (xiechuanxiao@caas.cn)