Sugarcane (Saccharum spp.), and Sugarcane Smut (Ustilago scitaminea Sydow) the Infection Process, Screening for Resistance, Disease Resistance and Possible Resistance Mechanisms

The interaction between sugarcane and sugarcane smut has been studied for over 130 years, yet we have not fully understand the complete defense mechanisms used by sugarcane plants against the fungus. This article outlines a brief history of sugarcane, sugarcane smut –an overview-, the infection process, some assessment methods for resistance, resistance of sugarcane to smut and there are proposed resistance mechanisms that might be operating at each stage of the colonization of the fungus in the sugarcane plant. The results based on what research has shown, indicate that there is preform and induce resistance operating in the sugarcane-Ustilago scitaminea system, both structural and chemical. It is determined that the resistance of sugarcane-to-sugarcane smut is multifactorial and the b pathogen elicits non-specific responses. The 5 step proposed resistance mechanisms involves (a) the role of morphological structure of the bud as it impedes smut spore germination or possibly delay the infection process, (b) the mechanisms used to impede or prevent spore germination on the bud surface, possibly involve diffused substances both preformed and induced. The induced substances being known phytoalexins, (c) the response mechanisms in the sugarcane bud to prevent the establishment of fungal mycelia-hypersensitive response, phytoalexins (phenolics) accumulation, lignification –induced responses, (d) the prevention of mycelia growth in the stalk-Gels and tyloses, glucanases and peroxidases, oxidative burst and savaging, callose deposition, (e) the resistance that might be operating to prevent smut whip formation-antitoxins, hormones, peroxide vessels, oxidative burst and scavenging, callose deposition and possibly papillae. In this overview there is the use Ustilago scitaminea to represent sugarcane smut although Sporisorium scitamineum is mentioned in some of references.