Transgenic Pyramiding for Crop Improvement

In recent years, transgenic pyramiding or stacking technology has gradually developed with the rapid development of genetically modified (GM) crops. This technology has unique advantages compared with the transgenic technology of a single gene. Transgenic pyramiding technology can simultaneously modify several traits of a crop, particularly the metabolic pathways and yield traits that are usually controlled by multiple genes. A batch of second generation GM crops with stacked traits has been commercialized, which mainly include resistances to pest and herbicide, and exhibit great application potential of transgenic pyramiding breeding. The present stacked GM crops are developed mainly through the integrated use of vector-based pyramiding and molecular marker assisted selection (MAS) based crossing/backcrossing pyramiding. Advances of vector based pyramiding technologies have been achieved on large capacity vectors, multiple-gene assembling, plastid transformation, polyprotein expression system and combinatorial genetic transformation. The combination of transgenic pyramiding and MAS-based pyramiding will help to effectively pyramid more targeted genes together. The advance of single nucleotide polymorphism (SNP) discovery and detecting technology has greatly promoted the MAS-based pyramiding in crop breeding. The rapid development of commercialized stacked GM crops, plant metabolic engineering and crop improvement for disease resistance have proved the successful applications of transgenic pyramiding. The present review discusses the advances of transgenic pyramiding technology, the application of transgenic pyramiding in crop improvement and the prospects and challenges of transgenic pyramiding breeding.