Differential gene expression in soybean infected by Phakopsora pachyrhizi in response to acibenzolar‐S‐methyl, jasmonic acid and silicon

Abstract

AbstractAsian soybean rust (ASR), caused by Phakopsora pachyrhizi, has negatively impacted soybean production worldwide. This study evaluated the effect of foliar spray of acibenzolar‐S‐methyl (ASM) and jasmonic acid (JA) as well as silicon (Si) supplied, either by soil amendment using calcium silicate or through a nutrient solution, on ASR control as well as on the expression of some defence‐related genes (phenylalanine ammonia‐lyase (PAL), chitinase (CHI), chalcone isomerase (CHAL), lipoxygenase (LOX), pathogenesis‐related protein 1 (PR‐1) and metalloproteinase (MET)) in soybean plants infected or not by P. pachyrhizi. Foliar Si concentration ranged from 2.6 to 8.7 dag/kg for Si supply by soil application or through a nutrient solution in comparison with the control treatment (no Si supply). Higher foliar Si concentration contributed to reducing ASR severity greater than 30%, mainly if supplied through nutrient solution. The ASR severity was significantly reduced by 36% with the ASM spray in comparison with the control treatment without any expressive effect on the expression of the analysed genes. The JA spray did not result in reduction on ASR severity in comparison with the control treatment even though with higher transcript levels of PAL at 12 hai. The transcripts levels of MET and PAL were significantly higher for inoculated plants taking up Si from the soil in comparison to non‐inoculated plants of this treatment at 72 hai. For Si supply through the nutrient solution (+Si plants), the transcripts levels of LOX and CHAL were significantly higher for inoculated plants in comparison to inoculated ‐Si ones at 12 hai. At 141 hai, the transcript level of PAL was significantly higher for inoculated + Si plants in comparison to inoculated ‐Si ones. In conclusion, Si supply contributed decisively to reduce ASR severity through the potentiation of some defence‐related genes mainly PAL and CHAL involved, respectively, in the biosynthesis of phenolics and flavonoids.