Role of Epigenetics in Crop Improvement

It is time to start to take into consideration the role of epigenetics in breeding programs. So far, various authors have reported hereditable gene silencing phenomena generally affecting qualitative traits. Usually the genes involved in these phenomena determine characters which can easily be scored by visual inspection, such as modifications in the plant architecture and pigment accumulation, or characters like the loss of antibiotic resistance. But we have to take into account that the majority of genes are involved in the determination of quantitative characters, and the phenotypic modifications caused by QTL silencing will result in subtle variations which are difficult to detect. For this reason it would be very hard to find silencing phenomena involving quantitative traits. Therefore, assuming that epigenetics concerns not only the qualitative but also the quantitative traits, this phenomenon must be taken into account in breeding programs. In particular, the transcriptional state of the different epialleles should be considered. This chapter will start by defining what we mean by epigenetics, as numerous definitions are now used, starting from the original definition of Waddington and adapting the definition to the different fields of study. We will then describe the epigenetics marks, before going into more detail of the epigenomic studies on two model plants, arabidopsis and rice. Then we will present data concerning the interaction of epigenetics and the environment and the role of the epigenetic phenomena on crops and in particular, on yield improvement. A brief paragraph on the epigenetic phenomenon called paramutation will conclude the chapter.

Keywords: Crop improvement, Epiallele, Epigenetics, Gene silencing, Paramutation.