One of the most popular ornamental plants worldwide, roses (Rosa sp.), are very susceptible to Botrytis gray mold disease. The necrotrophic infection of rose petals by B. cinerea causes the collapse and death of these tissues in both the growth and post-harvest stages, resulting in serious economic losses. To understand the molecular basis of rose resistance against B. cinerea, we profiled the petal transcriptome using RNA-Seq technology. We identified differentially transcribed genes (DTGs) in petals during B. cinerea infection at 30 h post inoculation (hpi) and/or 48 hpi. Gene ontology term enrichment and pathway analyses revealed that metabolic, secondary metabolite biosynthesis, plant-pathogen interaction, and plant hormone signal transduction pathways were involved. The expression of 370 cell-surface immune receptors was upregulated during infection. In addition, 188 genes encoding transcription factors were upregulated, particularly in the ERF, WRKY, bHLH, MYB, and NAC families, implying their involvement in resistance against B. cinerea. We further identified 325 upregulated DTGs in the hormone signal transduction pathways. Among them, the brassinosteroid (BR)-related genes were the most significantly enriched. To confirm the role of BR in Botrytis resistance, exogenous BR was applied to rose flowers before the inoculation of B. cinerea, which enhanced the defense response in these petals. Our global transcriptome profiling provides insights into the complex gene regulatory networks mediating the rose petal response to B. cinerea. We further demonstrated the role of the phytohormone BR in the resistance of petals to necrotrophic fungal pathogens.

Rosa hybrida is a valuable ornamental, food and medicinal crop worldwide, but with relatively limited molecular marker resources, especially for flower-specific markers. In this study, we performed genomic and floral transcriptomic sequencing of modern rose. We obtained comprehensive nucleotide information, from which numerous potential simple sequence repeat (SSR) markers were identified but were found to have high rates of amplification failure and PCR product redundancy. We applied a filtering strategy for BLAST analysis with the assembled genomic sequence and identified 124,591 genomic and 2,292 EST markers with unique annealing sites. These markers had much greater reliability than those obtained before filtering. Additional BLAST analysis against the transcriptomic sequences uncovered 5225 genomic SSRs associated with 4100 transcripts, 2138 of which were associated with functional genes that were annotated against the non-redundant database. More than 90% of these newly developed molecular markers were polymorphic, based on PCR using a subset of SSRs to analyze tetraploid modern rose accessions, diploid Rosa species and one strawberry accession. The relationships among Rosa species determined by cluster analysis (based on these results) were in agreement with modern rose breeding history, whereas strawberry was isolated in a separate cluster, as expected. Our results provide valuable molecular-genetic tools for rose flower trait improvement, breeding and taxonomy. Importantly, we describe a reproducible organ-specific strategy for molecular marker development and selection in plants, which can be applied to other crops.

In China, winter brings selling season of cut flowers as it is customary to have living blooms for lunar New Year celebrations. Here, lily is one of the most popular new year flowers and captured over 19 percent of all flower sales. The flower market of Beijing is the largest in China and therefore many lily farms are present in the suburb of Beijing to reduce logistical cost. During winter of 2015, lily plants exhibited leaf blight symptoms in greenhouses of a lily farm at Changping District (116°12′E, 40°13′N), Beijing. The disease has resulted in serious loss of lily production in the farm, and approximately 10 to 15 percent of plants were destroyed due to the severe infection. The infection initially manifested as irregular lesions on the leaves, which gradually expanded into blight of grayish brown and frequently involve the entire leaf. Severely infected leaves were distorted, covered with grey mycelium and conidia. Flower buds had no lesions or sporulation. Conidia were hyaline, unicellular and ovo...

Gray mold caused by Botrytis cinerea severely limits the postharvest quality of rose, but the contribution of ATP-binding cassette (ABC) transporters to rose defense remains unclear. Here, we identified 185 RcABC genes in the Rosa chinensis genome and classified them into eight subfamilies, with RcABCG as the largest subfamily. DESeq2-based RNA-seq analysis identified 13 significantly upregulated RcABC genes in response to B. cinerea infection at 48 hpi, nine of which belonged to the RcABCG subfamily. At 48 hpi, the log₂ fold changes of these induced genes ranged from 1.34 to 7.98, and RcABCG5, RcABCG50, RcABCG59, and RcABCG60 were selected for functional analysis. Further phylogenetic, gene-structure, and promoter analyses showed that several full-size RcABCG members were closely related to previously reported defense-associated ABCG transporters and harbored predicted GA-, MeJA-, and ABA-responsive cis-elements. Virus-induced gene silencing reduced the relative transcript levels of RcABCG5, RcABCG50, RcABCG59, and RcABCG60 to 22.8%, 17.9%, 35.2%, and 27.5% of the TRV-GFP control, respectively. Mean lesion area increased from 39.27 mm² in TRV-GFP discs to 44.96, 46.95, and 43.23 mm² in RcABCG5-, RcABCG50-, and RcABCG59-silenced discs, respectively, whereas no significant lesion increase was observed in RcABCG60-silenced discs. Together, these results establish a genome-wide framework for defense-related ABC transporters in rose and identify RcABCG5/50/59 as candidate genes associated with gray mold resistance under VIGS conditions.