02220naa a2200157 a 450000100080000000500110000800800410001910000220006024500610008226000090014352017720015270000150192470000200193970000180195977300850197716519232004-04-16       1998    bl uuuu     u00u1 u    #d1 aGOMEZ-VASQUEZ, R.  aBiochemical components of disease resistance of cassava.  c1998  aResistant genotypes offer the only durable, practicable means of controlling Xanthomonas bacterial bligth, but the nature of defences of cassava to this and to other diseases are virtually unknown. Suspension cultured cells in vitro show a series of resistance related responses to a range of microbial elicitors such as glucans from yeast and Colletotrichum, and to certain endogenous elicitors such as oligogalacturonides, jasmonic acid and glutathione. Surprisingly, pure LPS was ineffective but crude commercial EPS [xanthan] had effect. Auxin levels had a profound influence on intensity of cellular responses. This facile system has revealed a rapid [from 3 mins] and intensive, extracellular oxidative burst [as MO2] which can function as a first fine of defence by creating toxic Conditions, cross-linking cell wall components and as a diffusible signal. Subsequently, defence-related genes such as PAL are induced which may contribute to formation of flavonoids and antibacterial compounds. The oxidative burst may derive in part from the increased activity or production of peroxidase or from xanthine oxidase which is constitutive; gene[s] for the latter are under study. Similarly, in plants in response to incompatible bacterial pathogens, there is rapid generation of peroxide associated with plant cell walls, as revealed by cerium chloride and transmission EM; other localised increased were in peroxidase, PAL and its mRNA [revealed by in situ hybridisation], flavonoids and unknown antibacterial compounds. Catalase was down-regulated which may serve to maintain high levels of peroxide. Latex is readily released on cell damage and contains constitutuve Iysozyme but it has relatively little effect on X campestris pv. manihotis [syn. Xanonopodis].1 aDAY, R. C.1 aBEECHING, J. R.1 aCOOPER, R. M.  tRevista Brasileira de Mandioca, Salvadorgv. 17, p. 40, nov., 1998., Suplemento.