Abstract
Herbaceous peony (Paeonia lactiflora Pall.) is a well-known traditional flower in China and is widely used for landscaping and garden greening due to its high ornamental value. However, disease spots usually appear after the flowering of the plant and may result in the withering of the plant in severe cases. This study examined the disease incidence in an herbaceous peony field in the Yangzhou region, Jiangsu Province. Based on morphological characteristics and molecular data, the disease in this area was identified as a gray mold caused by Botrytis cinerea. Based on previously obtained transcriptome data, eight libraries generated from two herbaceous peony cultivars ‘Zifengyu’ and ‘Dafugui’ with different susceptibilities to the disease were then analyzed using digital gene expression profiling (DGE). Thousands of differentially expressed genes (DEGs) were screened by comparing the eight samples, and these genes were annotated using the Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) database. The pathways related to plant-pathogen interaction, secondary metabolism synthesis and antioxidant system were concentrated, and 51, 76, and 13 disease resistance-relevant candidate genes were identified, respectively. The expression patterns of these candidate genes differed between the two cultivars: their expression of the disease-resistant cultivar ‘Zifengyu’ sharply increased during the early stages of infection, while it was relatively subdued in the disease-sensitive cultivar ‘Dafugui’. A selection of ten candidate genes was evaluated by quantitative real-time PCR (qRT-PCR) to validate the DGE data. These results revealed the transcriptional changes that took place during the interaction of herbaceous peony with B. cinerea, providing insight into the molecular mechanisms of host resistance to gray mold.
Highlights
Botrytis cinerea Pers. (teleomorph: Botryotinia fuckeliana Fuck.), which leads to gray mold on various host plants [1], is considered one of the most important fungal plant pathogens worldwide [2]
Brown rot was due to high humidity, while the gray molds grew on the infected positions (Fig 1C); when the humidity decreased, the infected positions wizened and turned brown or yellow (Fig 1D)
The colonies formed spores; conidiophores were scattered or tufty, erect in shape and gray or pale brown in color; the tops of conidiophores consisted of 1~2 branches, and the terminal branch expanded with dense small sporophores, while a large number of conidia generated grape spikes; the conidia were ovoid or elliptical in shape, colorless or grayish brown in color, and 7~14μm×4~9μm in size (Fig 2D–2F)
Summary
Botrytis cinerea Pers. (teleomorph: Botryotinia fuckeliana (de Bary) Fuck.), which leads to gray mold on various host plants [1], is considered one of the most important fungal plant pathogens worldwide [2]. Plants evolve several mechanisms to cope with B. cinerea stress, and these mechanisms are all achieved by induction of numerous disease resistance genes involved in various pathways [5,6,7,8]. A WRKY family gene that responds to B. cinerea infection, (Solanum lycopersicum defense-related WRKY1) SlDRW1, is significantly up-regulated by the defense response of tomato, and the silencing of this gene increases the severity of gray mold [8]. De Cremer et al [6] show that genes involved in the phenylpropanoid pathway and terpenoid synthesis are transcribed in lettuce in response to a challenge by B. cinerea. The above studies reflect that disease resistance-relevant genes are highly effective against B. cinerea in host plants
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