Mutation Induction in Coffea arabica L. Using in Vivo Grafting and Cuttings

Abstract Coffee leaf rust (CLR) caused by the obligate parasite, the biotrophic Hemileia vastatrix Berk. & Broome (Basidiomycetes: Pucciniales), is the most devastating disease of Coffea arabica L. Breeding resistant varieties is one of the most economic and environment friendly means to control the disease. However, this is challenged by the loss of resistance after a short period in commercial production. Catimor CIFC7963, an elite, leaf rust resistant Coffea arabica L. variety, has been cultivated in China for decades, which has resulted in the breakdown of its disease resistance. Due to the lengthy breeding process of coffee, the development of new resistant varieties is arduous. Physical and chemical mutagenesis offers an alternative means to more rapidly create novel and beneficial genetic variations. Bud grafting is a propagation technique frequently used for woody plants whereby a bud of one plant is attached to the rootstock of another plant. Likewise, cutting is a frequently used propagation technique. In coffee, physical irradiation of the bud followed by grafting or cutting can accelerate the mutation breeding process, as cutting or grafting increases the growth rate without affecting the major traits of the background varieties. Here, we present protocols to induce mutations on buds of the C. arabica variety Catimor CIFC7963 by gamma-ray irradiation and their subsequent propagation through cutting or bud grafting.