Peronospora parasitica

BOTELLA, M. A., PARKER, J. E FROST, L. N BITTNER-EDDY, P. D BEYNON, J. L., DANIELS, M. J., HOLUB, E. B, JONES, J. D. G., Three genes of the Arabidopsis RPP1 complex resistance locus recognize distinct Peronospora parasitica avirulence determinants., Plant Cell., 1998,10, 1847-1860. 

The nonprotein amino acid, / -aminobutyric acid (BABA) protected Arabidopsis against the oomycete pathogen Peronospora parasitica through activation of natural defence mechanisms of the plant such as callose deposition, the hepersensitive response, and the formation of the trailing necroses [158]. Seed treatment with BABA also shown to protect Pennisetum glaucum (pear millet) systematically from the attack of Sclerospora graminicola [159]. 

The importance of SA in the activation of resistance was further underscored by the demonstration that otherwise resistant Arabidopsis plants become susceptible to Peronospora parasitica when phenylalanine ammonia lyase (PAL) activity is specifically inhibited by 2-aminoindan-2-phosphonic acid [77]. Since PAL catalyzes the first step in the SA biosynthetic pathway and resistance was restored in these PAL-suppressed plants by exogenous application of SA, increased susceptibility is presumably caused by a block in SA synthesis. Likewise, tobacco plants exhibiting epigenetic suppression of PAL gene expression due to cosuppression do not develop SAR in response to TMV infection [78]. In addition, these plants fail to systemically express the PR-la gene after TMV infection. 

Tobacco was reciprocally protected against TMV, TNV, or Thielaviopsis basicola (34) against Phytophthora parasitica var. nicot ianae with TNV (63) and against TMV and E r y s i p h e cichoracearum (powdery mildew) with Peronospora tabacina (64-66). 

Tobacco blue mold tobacco mosaic tobacco ringspot black shank black root rot Peronospora tabacina 5 virus virus Phytophthora parasitica Thielaviopsis basicola, 31,32 1.3 1.3 33 34... 

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