Unraveling the Sclerotinia Basal Stalk Rot Resistance Derived From Wild Helianthus argophyllus Using a High-Density Single Nucleotide Polymorphism Linkage Map.

Yuan Liu,Zahirul I Talukder,Xiwen Cai,Gerald J Seiler,Lili Qi,William Underwood,Christopher G Misar,Xuehui Li

doi:10.3389/fpls.2020.617920

Abstract

Basal stalk rot (BSR), caused by the fungus Sclerotinia sclerotiorum, is a serious disease of sunflower (Helianthus annuus L.) in the humid temperate growing areas of the world. BSR resistance is quantitative and conditioned by multiple genes. Our objective was to dissect the BSR resistance introduced from the wild annual species Helianthus argophyllus using a quantitative trait loci (QTL) mapping approach. An advanced backcross population (AB-QTL) with 134 lines derived from the cross of HA 89 with a H. argophyllus Torr. and Gray accession, PI 494573, was evaluated for BSR resistance in three field and one greenhouse growing seasons of 2017–2019. Highly significant genetic variations (p < 0.001) were observed for BSR disease incidence (DI) in all field screening tests and disease rating and area under the disease progress curve in the greenhouse. The AB-QTL population and its parental lines were genotyped using the genotyping-by-sequencing method. A genetic linkage map spanning 2,045.14 cM was constructed using 3,110 SNP markers mapped on 17 sunflower chromosomes. A total of 21 QTL associated with BSR resistance were detected on 11 chromosomes, each explaining a phenotypic variation ranging from 4.5 to 22.6%. Of the 21 QTL, eight were detected for BSR DI measured in the field, seven were detected for traits measured in the greenhouse, and six were detected from both field and greenhouse tests. Thirteen of the 21 QTL had favorable alleles from the H. argophyllus parent conferring increased BSR resistance.

Highlights

Sunflower (Helianthus annuus L.) ranks third in worldwide production among the important vegetable oil-producing crops after soybean and rapeseed (USDA, 2020)
This research aims to map quantitative trait loci (QTL) associated with Sclerotinia Basal stalk rot (BSR) resistance segregating in an advanced backcross QTL (AB-QTL) mapping population developed from the cross of a highly BSR-resistant H. argophyllus accession with a cultivated sunflower line
The equation (i) is for BSR disease incidence (DI) measured in the field, and equation (ii) is for area under the disease progress curve (AUDPC) and disease rating (DR) measured in the greenhouse, where σg2 is the genotypic variance, σg2e is the genotype × environment variance, σe2 is the error variance, r is the number of replications, and l is the number of environments

Summary

Introduction

Sunflower (Helianthus annuus L.) ranks third in worldwide production among the important vegetable oil-producing crops after soybean and rapeseed (USDA, 2020). A root infection initiated by myceliogenic germination of sclerotia (unique to sunflower) causes basal stalk rot (BSR) and wilt, while carpogenic germination of sclerotia releases airborne ascospores and causes midstalk rot (MSR) by infecting sunflower leaves or head rot (HR) by infecting capitula (Gulya et al, 1997). All these diseases can cause serious economic damage to sunflower by both yield loss and reduced seed quality

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