Forward and reverse genetics in crop breeding

Abstract

The ability to identify, study, create and utilize genetic variation are arguably fundamental aspects in the development of human beings. Traditional, or forward, genetics has its roots in man’s first attempts at the domestication of plants and animals. Novel and preferred traits such as the lack of seed shattering were selected from large populations and maintained for future propagation, leading to the first cultivars. The discovery of DNA as the heritable material thousands of years later enabled the development of reverse genetics whereby targeted lesions in the genome are recovered to test and utilize functional variation in genes. A major contributor to both forward and reverse genetics was the discovery in the early twentieth century that mutations can be induced in genomes at frequencies in several orders of magnitude higher than typically observable in nature. The ability to produce novel variation has fueled the development of thousands of new crop cultivars. Examples exist of increased disease resistance, higher yields, tolerance to abiotic stresses such as drought and salinity and improved nutritional quality. In an era where global food security is threatened by climate change and variation and growing populations, use of induced mutations is an important method in the breeder’s toolbox. This review describes the use of induced mutations for forward and reverse genetics in plants, with a focus on crops. Different mutagens and random versus targeted approaches are described. Additionally, newly emerging methods and technologies are discussed that promise to advance basic and applied plant sciences.