Mapping QTL associated with partial resistance to Aphanomyces root rot in pea (Pisum sativum L.) using a 13.2K SNP array and SSR markers.

Longfei Wu,Robert L Conner,Debra L Mclaren,Sheau-Fang Hwang,Rudolph Fredua-Agyeman,Kan-Fa Chang,Stephen E Strelkov

doi:10.1007/s00122-021-03871-6

Abstract

A stable and major QTL, which mapped to an approximately 20.0cM region on pea chromosome 4, was identified as the most consistent region conferring partial resistance to Aphanomyces euteiches. Aphanomyces root rot (ARR), caused by Aphanomyces euteiches Drechs., is a destructive soilborne disease of field pea (Pisum Sativum L.). No completely resistant pea germplasm is available, and current ARR management strategies rely on partial resistance and fungicidal seed treatments. In this study, an F8 recombinant inbred line population of 135 individuals from the cross 'Reward' (susceptible) × '00-2067' (tolerant) was evaluated for reaction to ARR under greenhouse conditions with the A. euteiches isolate Ae-MDCR1 and over 2years in a field nursery in Morden, Manitoba. Root rot severity, foliar weight, plant vigor and height were used as estimates of tolerance to ARR. Genotyping was conducted with a 13.2K single-nucleotide polymorphism (SNP) array and 222 simple sequence repeat (SSR) markers. Statistical analyses of the phenotypic data indicated significant (P < 0.001) genotypic effects and significant G × E interactions (P < 0.05) in all experiments. After filtering, 3050 (23.1%) of the SNP and 30 (13.5%) of the SSR markers were retained for linkage analysis, which distributed 2999 (2978 SNP + 21 SSR) of the markers onto nine linkage groups representing the seven chromosomes of pea. Mapping of quantitative trait loci (QTL) identified 8 major-effect (R2 > 20%), 13 moderate-effect (10% < R2 < 20%) effect and 6 minor-effect (R2 < 10%) QTL. A genomic region on chromosome 4, delimited by the SNP markers PsCam037549_22628_1642 and PsCam026054_14999_2864, was identified as the most consistent region responsible for partial resistance to A. euteiches isolate Ae-MDCR1. Other genomic regions important for resistance were of the order chromosome 5, 6 and 7.

Highlights

Field pea or “dry pea” (Pisum sativum L.) is an economically important cool-season legume crop that is cultivated widely in different parts of the world (Hossain et al 2012)
This study evaluated tolerance or partial resistance to Aphanomyces root rot (ARR) in an F8 recombinant inbred line (RIL) population, with this resistance derived from the partially resistant parent ‘00-2067’ (2013)
Significant genetic effects within the RIL populations were detected for root rot severity, foliar weight, vigor and plant height

Summary

Introduction

Field pea or “dry pea” (Pisum sativum L.) is an economically important cool-season legume crop that is cultivated widely in different parts of the world (Hossain et al 2012). The production of field pea is affected adversely by the pea root rot complex (PRRC) (Bailey et al 2003; Xue 2003; Chang et al 2013; Wu et al 2018). Is a dominant pathogen in the PRRC (Jones and Drechsler 1925) This pathogen is favoured by saturated soil conditions and poor drainage. In Canada, Aphanomyces root rot (ARR) outbreaks have been reported only recently, either because pea production in the same fields over multiple years resulted in a buildup of the pathogen, or because symptoms of ARR can be better distinguished from other root rot pathogens (Hwang and Chang 1989; Xue 2003; Chatterton et al 2015; Wu et al 2017). The uptake of water and nutrients in diseased plants is reduced, which can result in wilting and death of the plants (Chatterton et al 2015)

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