2017 ASHS Annual Conference
Concept of Precision Breeding
Concept of Precision Breeding
Wednesday, September 20, 2017: 4:00 PM
Kohala 4 (Hilton Waikoloa Village)
The term ‘precision breeding’ (PB) was coined in 2004 by Dr. Tony Conner at the New Zealand Institute for Crop & Food Research and described a simple concept – the manipulation of discrete desirable traits for plant improvement by transfer of controlling genetic sequences identified among species that are sexually compatible. However, the knowledge and tools required to accomplish PB were still in development in 2004 so that little actual progress occurred. Only recently has it become possible to create precision-bred plants and this capability is increasing rapidly worldwide. The advent of tools, such as those for genome sequencing, transcriptome analysis and gene editing, as well as a host of other technologies, has not only facilitated PB, but, importantly, allowed the concept of PB to be explained simply and clearly in light of basic biological terminology. Therefore, the following mechanisms, some of which still are commonly disputed as being unsafe or to cause ‘undesirable consequences’, can be explained and managed in context of the natural plant lifecycle. First, PB utilizes the comparatively stable plant mitotic cell division cycle to insert target DNA. This avoids the plant’s meiotic pathway, which, by evolutionary design, is meant to introduce random variation into plant populations. Second, the introduction of more than one copy of a desired genetic insert is of no biological consequence considering recent discoveries that the plant genome is already rife with multiple copies of genes and their regulatory sequences. Third, similarly, whether or not an insert disrupts an existing genetic element is of little consequence because such disruptions commonly occurs in nature via the evolutionary mechanisms of variation - crossing-over and transposition, which are well-known to commonly disrupt existing genetic sequences during meiosis and lead to lethality. Fourth, as with conventional breeding, individual plants expressing desired traits must be selected from a larger population of modified individuals. Compared to any other method of plant improvement, only PB provides precise transfer and selection of specific traits among related species. In a sense, PB is akin to the selection of mutations (sports) formed during mitosis that have led to improved cultivars. However, PB provides precise manipulation of traits that need not be visualized to in order to select, or may not occur, in sports. Taken as a whole, PB is functionally similar, but significantly more benign than any other method of plant genetic improvement because it specifically transfers only desired traits that preexist in natural populations.