Abstract: The invention consists in modifying the levels of accumulation and emission of monoterpenes and sesquiterpenes in citrus as a mechanism to achieve systemic resistance against pathogens or repellency against pests. The alteration of the content of d-limonene and other terpenes is achieved by genetic transformation via the introduction of a gene that encodes an enzyme with d-limonene synthase activity, from a citrus fruit or plant or from another living organism, in antisense or RNAi (RNA interference) configuration. Genetic modification is achieved either by Agrobacterium tumefaciens or any other method of genetic transformation of plants from protoplasts or explants. The construction is incorporated in citrus genotypes or related genera of the family Rutaceae in order to reduce the levels of accumulation and emission of the monoterpene and precursor compounds and/or derivatives, either of leaves or flowers and/or fruit.