Biotechnology for a pesticide free orchard: a promise or an utopia?
Apple production in temperate climate with often wet springs needs a relevant input of fungicides to control apple scab and powdery mildew. Additionally if weather conditions are particularly warm and wet around flowering time fire blight, caused by Erwinia amylovora may cause severe damage to the plantations. Classical breeding has produced many scab resistant cultivars overwhelmingly based on the resistance from M. floribunda 821 (Vf) and some mildew resistant cultivars and efforts to breed also fire blight resistant cultivars are currently undertaken. Such cultivars are mainly used in organic production however have little global impact. Marker assisted selection added a relevant quality by shortening time and allowing pyramiding of resistance genes. If the development of markers for MAS was the primary goal of genetic analysis in the 90's, identification and cloning of resistance genes is now the goal. Three resistance genes have been isolated and cloned into a susceptible apple cultivar: HcrVf2 and Vr2_C responsible for the Vf and Rvi15 scab resistance, respectively, and the fire blight resistance gene FB_RM5 from Malus × robusta 5. All these cloned resistance genes could now be pyramided into a single cultivar through genetic engineering. The results demonstrate that introduction of apple own genes with their own regulatory sequences without the presence of foreign genes in the end product (cisgenic) is possible and a popular cultivar can be ameliorated through addition of genes by genetic engineering. The used methodology allows the sequential addition of genes; e.g. a second or more transformations. First field trials show that the Vf scab resistance is, as we expect, also holding up in the field assuming absence of Vf overcoming races of the scab fungus. However even if currently no indication of any negative effect can be demonstrated or even postulated, the general opposition against GMO, and the rather cumbersome legislation requests, hampers the development of a cisgenic disease resistant apple cultivar. Public opinion enhanced by particular active groups is based on misconception of the general danger of the technology and not on the true value (or added value) of the product. In the case of apple this added value would be a relevant reduction of pesticide input in the orchard.
Gessler, C. 2017. Biotechnology for a pesticide free orchard: a promise or an utopia?. Acta Hort. (ISHS) 1172:1-8
genetic modification, Venturia inaequalis, Erwinia amylovora, apple, cisgenic