Search

Phytophthora capsici (Leonian), classified as an oomycete, seriously threatens the production of pepper (Capsicum annuum). Current understanding of the defense responses in pepper to P. capsici is limited. In this study, RNA-sequencing analysis was utilized to identify differentially expressed genes in the resistant line “PI 201234”, with 1220 differentially expressed genes detected. Of those genes, 480 were up-regulated and 740 were down-regulated, with 211 candidate genes found to be involved in defense responses based on the gene annotations. Furthermore, the expression patterns of 12 candidate genes were further validated via quantitative real-time PCR (qPCR). These genes were found to be significantly up-regulated at different time points post-inoculation (6 hpi, 24 hpi, and 5 dpi) in the resistant line “PI 201234” and susceptible line “Qiemen”. Seven genes were found to be involved in cell wall modification, phytoalexin biosynthesis, symptom development, and phytohormone signaling pathways, thus possibly playing important roles in combating exogenous pathogens. The genes identified herein will provide a basis for further gene cloning and functional verification studies and will aid in an understanding of the regulatory mechanism of pepper resistance to P. capsici.

Phytophthora blight is one of the most destructive diseases affecting pepper production. Exploring resistance genes and transferring them into cultivated lines are critical for pepper (Capsicum annuum L.) breeding and disease control. To understand the genetics of resistance to Phytophthora capsici race 2 in pepper line PI201234 and identify molecular markers that are tightly linked to the gene, an F2 population containing 794 individuals was developed by crossing a susceptible line, Shanghaiyuan, to PI201234. Genetic analysis indicated that the resistance in PI201234 to P. capsici race 2 was controlled by a dominant gene, tentatively named CaPhyto. Using 12 markers, comprising 10 SSR markers, one CAPS marker, and one dCAPS marker, the gene was mapped to a 3.3-cM interval on chromosome 5. Based on genome sequence annotations in pepper line Zunla-1 and transcriptional expression analysis, two genes, Capana05g000764 and Capana05g000769, were identified as candidate genes. One SSR marker, ZL6726, most closely linked to CaPhyto at a distance of 1.5 cM, was validated to be a reliable marker for selecting phenotypes of resistance to P. capsici race 2. The results obtained in the present study will facilitate cloning and marker-assisted selection for resistance genes in pepper.

Background The use of cytoplasmic male sterility (CMS) in F1 hybrid seed production of chili pepper is increasingly popular. However, the molecular mechanisms of cytoplasmic male sterility and fertility restoration remain poorly understood due to limited transcriptomic and genomic data. Therefore, we analyzed the difference between a CMS line 121A and its near-isogenic restorer line 121C in transcriptome level using next generation sequencing technology (NGS), aiming to find out critical genes and pathways associated with the male sterility. Results We generated approximately 53 million sequencing reads and assembled de novo, yielding 85,144 high quality unigenes with an average length of 643 bp. Among these unigenes, 27,191 were identified as putative homologs of annotated sequences in the public protein databases, 4,326 and 7,061 unigenes were found to be highly abundant in lines 121A and 121C, respectively. Many of the differentially expressed unigenes represent a set of potential candidate genes associated with the formation or abortion of pollen. Conclusions Our study profiled anther transcriptomes of a chili pepper CMS line and its restorer line. The results shed the lights on the occurrence and recovery of the disturbances in nuclear-mitochondrial interaction and provide clues for further investigations.