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Published on: August 4, 2018
Characterization of resistance to bacterial panicle blight in rice revealed by transcriptome and QTL mapping analyses
John Ontoy1,2, Jobelle Bruno1,2, Bishnu Shrestha1,2
1Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge, LA, United States.
Introduction:
Bacterial panicle blight (BPB) is a chronic disease of rice caused by the bacterial pathogen Burkholderia glumae. While rice varieties grown in the United States are mostly susceptible to BPB, a medium-grain variety Jupiter shows a moderate resistance phenotype. However, its underlying defense mechanisms and genetic traits are not known well.
Methods:
This study combined transcriptomic and genetic analyses to characterize the moderate BPB resistance of Jupiter. Comparative RNA-seq analysis of Jupiter and Bengal (a BPB susceptible medium-grain variety) was performed using panicle samples collected 24 hours post pathogen-inoculation at the flowering stage. We also conducted quantitative trait locus (QTL) mapping of the BPB resistance, using a recombinant inbred line (RIL) population from Jupiter and Bengal.
Results And Discussion:
The results indicated that enhanced expression of genes involved in defense and stress response was associated with the partial resistance to BPB. Among the six QTLs identified for BPB resistance, qBPB3.2 on Chromosome 3 was consistently detected across multi-year trials. Notably, this QTL was also located close to a major locus previously reported in studies using different mapping populations. The genes within these QTL regions included putative stress-related genes potentially linked to a network of pathogenesis-related and abiotic stress responsive regulators that were differentially expressed between the parents. Nevertheless, none of the candidate genes present in these genomic regions were identified as DEGs from the transcriptome analysis, suggesting their involvement in BPB resistance through unknown mechanisms beyond direct transcription in response to pathogen infection. This study provides valuable insights into environmentally responsive regulators and their complex interactions underlying resistance to BPB, highlighting the broad physiological impact of the pathogen infection on the host.
