Abstract
This study broadens the knowledge of plant-pathogen interactions using phytohormone-deficient and low-sensitivity mutant tomatoes. The experiment was performed under greenhouse conditions and the mutants used were provided by the HCPD laboratory, at ESALQ/USP. The hormone mutant Never ripe showed a larger final lesion size when inoculated with Botrytis cinerea, whereas curl3 was relatively resistant to this pathogen and more susceptible when inoculated with Phytophthora infestans. The transgenic 35S :: nahG was more susceptible to Oidium lycopersici, and the double mutant dgt, Nr more resistant. The low sensitivity to brassinosteroids confers greater susceptibility to P. infestans and higher resistance to B. cinerea. The deficiency of the hormone auxin promotes high resistance to diseases caused by O. lycopersici, P. infestans and B. cinerea.
Highlights
Despite the absence of an immune system similar to animals, plants have developed an impressive variety of defenses, conceived to detect invasive organisms and suppress pathogens before serious damage occurs (Freeman & Beattie, 2008)
The hormone mutants used were diageotropica – plants have low sensitivity to auxin; notabilis – plants present a low concentration of abscisic acid; Never ripe (Nr) – which has a low sensitivity to ethylene; epinastic – plants have an overproduction of ethylene; procera – plants present a constitutive response to gibberellins; curl3 – plants which carry the mutant allele are insensible to brassinosteroids; and 35S::nahG – plants with reduced levels of salicylic acid
Whereas biotrophic organisms are completely dependent of a living host for survival, necrotrophs cause cell death releasing phytotoxic compounds or enzymes that promote cell wall degradation and the release of nutrients which are necessary for growth (Vleeshouwers & Oliver, 2014)
Summary
Despite the absence of an immune system similar to animals, plants have developed an impressive variety of defenses, conceived to detect invasive organisms and suppress pathogens before serious damage occurs (Freeman & Beattie, 2008). This system coordinates, in an effective manner, the activation of specific defenses, minimizing the energy costs while the ideal resistance is reached (Pieterse & Dicke, 2007). The microorganisms that overcome this first defense barrier become pathogens which can present different types of parasitism as necrotrophic, hemi-biotrophic and biotrophic. Hemi-biotrophic pathogens present a transitory relationship between biotrophic and necrotrophic. These pathogens present, on the initial phase of infection, strategies similar to those observed on biotrophic pathogens, with the use of
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