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Research Project: Enhanced Disease and Abiotic Stress Resistance in Edible Legumes

Location: Grain Legume Genetics Physiology Research

Title: Exploring the genetics of lesion and nodal resistance in pea (Pisum sativum L.) to Sclerotinia sclerotiorum using genome-wide association studies and RNA-Seq

Author
item CHANG, HAO-XUN - MICHIGAN STATE UNIVERSITY
item SANG, HYUNKYU - MICHIGAN STATE UNIVERSITY
item WANG, JIE - MICHIGAN STATE UNIVERSITY
item MCPHEE, KEVIN - MONTANA STATE UNIVERSITY
item ZHUANG, XIAOFENG - THE OHIO STATE UNIVERSITY
item Porter, Lyndon
item CHILVERS, MARTIN - MICHIGAN STATE UNIVERSITY

Submitted to: Plant Direct
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2018
Publication Date: 6/27/2018
Citation: Chang, H., Sang, H., Wang, J., McPhee, K.E., Zhuang, X., Porter, L.D., Chilvers, M.I. 2018. Exploring the genetics of lesion and nodal resistance in pea (Pisum sativum L.) to Sclerotinia sclerotiorum using genome-wide association studies and RNA-Seq. Plant Direct. 2(6):e00064. https://doi.org/10.1002/pld3.64.
DOI: https://doi.org/10.1002/pld3.64

Interpretive Summary: White mold caused by Sclerotinia sclerotiorum is a major disease impacting pea production under both irrigated and dryland farming systems. Currently, commercial fresh and dry pea cultivars are extremely susceptible to infection by the white mold pathogen and fungicides can provide excellent but not complete control. The present research identified potential genes from a white mold-resistant pea line demonstrating two different resistance mechanisms believed to be used in peas to inhibit the colonization of plant tissue by S. sclerotiorum. A glutathione S-transferase gene was the principle gene discovered that was associated with two different forms of disease resistance. This research can be used to develop genetic markers for these resistance genes that can be used in marker-assisted selection of pea lines with multiple types of resistance to the white mold pathogen for incorporation into new and improved commercial pea lines.

Technical Abstract: Nodal resistance in plants is a phenomenon where a fungal infection is prevented from passing through a node and the infection is limited to an internode region. Nodal resistance has been observed in some pathosystems such as the pea (Pisum sativum L.)-white mold (WM) (Sclerotinia sclerotiorum (Lib.) de Bary) pathosystem. Other than nodal resistance, different pea lines display different levels of stem lesion length restriction, referred to as lesion resistance. It is unclear whether the genetics of lesion resistance and nodal resistance are identical or different. This study applied genome-wide association studies (GWAS) and RNA-Seq to understand the genetic makeup of these two types of resistance. The time series RNA-Seq experiment consisted of two pea lines (the susceptible ‘Lifter’ and the partially resistant PI 240515), two treatments (mock samples and WM inoculated samples), and three time points (12, 24, and 48 hours post- inoculation). Integrated results from GWAS and RNA-Seq analyses identified different redox-related transcripts for lesion and nodal resistances. A transcript encoding a glutathione S-transferase was the only transcript common to both resistance phenotypes. There were more up-regulated leucine rich-repeat containing transcripts found for lesion resistance, while different candidate resistance transcripts such as a VQ motif-containing protein and a myo-inositol oxygenase were found for nodal resistance. This study demonstrated the robustness of combining GWAS and RNA-Seq for identifying WM resistance in pea, and results suggest different genetics underlying lesion and nodal resistance.