| Popis: |
This chapter deals with recent studies on the biochemistry of disease resistance expression in Phaseolus vulgaris L., paying particular attention to the regulation of phytoalexin accumulation. Advantages of this system for biochemical studies are: (a) The disease resistance profile of P vulgaris has been characterised genetically to some extent (Meiners, 1981) and physiologically (Bailey, 1981). In particular, different cultivars (eg. Kievit, Immuna, Red Kidney) undergo highly specific interactions with physiological races of Colletotrichum lindemuthianum (eg. β,δ,γ) the causal agent of anthracnose disease of P. vulgaris. (b) The physiology of this interaction has been extensively studied using hypocotyls, the organ which together with leaves is the natural site of attack by C. lindemuthianum. There is strong evidence that the differential accumulation of the isoflavonoid derivative phaseollin and other structurally related phytoalexins such as phaseollidin, phaseollinisoflavan and kievitone in resistant and susceptible interactions plays a crucial role in the specificity of host resistance (Bailey, 1981). (c) Detailed study of the effects of phytoalexin inducing agents on phenylpropanoid metabolism in P. vulgaris hypocotyls indicates that accumulation of phytoalexins is a specific event, and the levels of most other phenylpropanoid products (eg. hydroxycinnamic acids) remain roughly constant relative to untreated control tissue (Rathmell and Bendall, 1971). |
