Host status of several green manure crops to <i>Heterodera schachtii</i> and green manure crop cultivation effect on nematode density

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Resistant and Susceptible Responses in Tomato to Cyst Nematode are Differentially Regulated by Salicylic Acid

To understand the machinery underlying a tomato cultivar harboring the Hero A gene against cyst nematode using microarrays, we first analyzed tomato gene expression in response to potato cyst nematode (PCN; Globodera rostochiensis) during the early incompatible and compatible interactions at 3 and 7 days postinoculation (dpi). Transcript levels of the phenylalanine ammonia lyase (PAL) and Myb-related genes were upregulated at 3 dpi in the incompatible interaction. Transcription of the genes encoding pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) was also upregulated at 3dpi in the incompatible interaction. On the other hand, the four genes (PAL, Myb, PDC and ADH) were downregulated in the compatible interaction at 3 dpi. When the expression levels of several pathogenesis-related (PR) protein genes in tomato roots were compared between the incompatible and compatible interactions, the SA-dependent PR genes were found to be induced in the incompatible interaction at 3 dpi. The PR-1(P4) transcript increased to an exceptionally high level at 3 dpi in the cyst nematode-infected resistant plants compared to the uninoculated controls. The free SA levels were elevated to similar levels in both incompatible and compatible interactions. We then confirmed that PR-1(P4) was not significantly induced in the NahG tomato harboring the Hero A gene, compared with the resistant cultivar. We thus found that PR-1(P4) was a hallmark for the cultivar resistance conferred by Hero A against PCN and that nematode parasitism resulted in the inhibition of the SA signaling pathway in the susceptible cultivars