Molecular Mechanisms for Resistance to Biotic Stresses

Diverse pathogens including viruses, viroids, fungi, and bacteria are responsible of diseases on Citrus. Some of them in addition represent a treath to Citrus industry in some specific areas, others are either worldwide spread or have a restricted distribution. Breeding program searching for resistance to a given pathogen must take into consideration the nature of the interaction being studied. In addition a large number of data generated by sequencing projects will contribute to the identification of individual genes or groups of genes potentially associated with resistance to biotic and abiotic factors. This chapter introduce the molecular basis of plant resistance to innate immune response elicited by non-specific elicitors and how successful pathogens have evolved to evade them or trigger them later in the infection so that they become infective. The other paragraphs are dedicated to illustrating three important disease model studies caused by a fungus (Alternaria brown rot), an oomycete (Phythophthora root rot) and a virus (Citrus Tristeza).