Iris is one of the most popular and best-selling ornamental plants around the globe. Fusarium root rot disease, Fusarium oxysporum f.sp. gladioli (FOG) is one of the most serious disease of Iridaceae and Iris plants. In this study, three resistant and three susceptible Iris genotypes were inoculated with FOG isolates to evaluate expression of related genes promoting defense to disease at intervals times at two, four and six weeks post inoculation. Total RNA was extracted using an AccuZol™ reagent, and the first-strand Cdna was synthesized accordingly. Expression level of WRKY transcription factors (WRKY), lectin receptor kinase (LecRK), pathogenesis-related protein (PR3), lipoxygenase (LOX1) and ribosome-inactivating proteins (RIP) genes was investigated using quantitative polymerase chain reaction (qPCR). The transcriptional level of five defense-related genes were up-regulated in FOG-infected samples. The genes expression in resistant Iris genotypes NIOP3, NIOP15 and NIOP16 was much higher than susceptible NIOP1, NIOP12 and NIOP20 genotypes. The highest level of expression was observed in all the genes and genotypes at 6 weeks post inoculation. The phenotypic symptoms of genotypes and changes in the expression of genes confirmed resistance in Iris genotypes NIOP3, NIOP15 and NIOP16 in comparison to susceptible genotypes NIOP1, NIOP12 and NIOP20, and un-inoculated control Iris plants. Identifying disease-resistant genotypes can contribute to the development of new ornamental cultivars that can be deployed to ensure high quality and lasting Iris plants.
Keywords: Bulb rot; Iris germanica; LOX1; LecRK; PR3; QRT-PCR; Root rot; WRKY.
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