Introgression and monitoring of wild Helianthus praecox alien segments associated with Sclerotinia basal stalk rot resistance in sunflower using genotyping-by-sequencing

Abstract

Sclerotinia basal stalk rot (BSR) and downy mildew are major diseases of sunflowers worldwide. Breeding for BSR resistance traditionally relies upon cultivated sunflower germplasm that has only partial resistance thus lacking an effective resistance against the pathogen. In this study, we report the transfer of BSR resistance from sunflower wild species, Helianthus praecox , into cultivated sunflower and molecular assessment of the introgressed segments potentially associated with BSR resistance using the genotyping-by-sequencing (GBS) approach. Eight highly BSR-resistant H . praecox introgression lines (ILs), H.pra 1 to H.pra 8, were developed. The mean BSR disease incidence (DI) for H.pra 1 to H.pra 8 across environments for four years ranged from 1.2 to 11.1%, while DI of Cargill 270 (susceptible check), HA 89 (recurrent parent), HA 441 and Croplan 305 (resistant checks) was 36.1, 31.0, 19.5, and 11.6%, respectively. Molecular assessment using GBS detected the presence of H . praecox chromosome segments in chromosomes 1, 8, 10, 11, and 14 of the ILs. Both shared and unique polymorphic SNP loci were detected throughout the entire genomes of the ILs, suggesting the successful transfer of common and novel introgression regions that are potentially associated with BSR resistance. Downy mildew (DM) disease screening and molecular tests revealed that a DM resistance gene, Pl 17 , derived from one of the inbred parent HA 458 was present in four ILs. Introgression germplasms possessing resistance to both Sclerotinia BSR and DM will extend the useful diversity of the primary gene pool in the fight against two destructive sunflower diseases.

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

“…However, none of these studies pursued detailed analysis of Sclerotinia resistance with respect to their genetic position in the sunflower genome nor released any germplasm lines to be utilized in practical breeding programs until recently. Introgression of BSR resistance has been achieved from H. argophyllus , H. petiolaris , and H. praecox into the cultivated sunflower background ( Qi et al, 2016b ; Talukder et al, 2019a ), and highly BSR-resistant introgression lines have been released for further use in sunflower breeding programs ( Qi et al, 2018 ; Talukder et al, 2019b ). In order to dissect the genetic basis of BSR resistance introgressed from H. argophyllus , we used an AB-QTL mapping population combined with GBS genotyping to identify 21 QTL associated with BSR resistance on 11 sunflower chromosomes in the present study, each explaining a phenotypic variation ranging from 4.5 to 22.6%.…”

“…Sclerotinia BSR disease is the most damaging in the humid temperate Northern Great Plains (North Dakota, South Dakota, and Minnesota) where most of the United States sunflower is grown. Fungicidal control of BSR disease is not feasible because the infection begins belowground ( Talukder et al, 2019a ). The use of host resistance is the most economic and environmentally friendly option for BSR management in sunflower.…”

Genomic Insights Into Sclerotinia Basal Stalk Rot Resistance Introgressed From Wild Helianthus praecox Into Cultivated Sunflower (Helianthus annuus L.)

“…runyonii accession (PI 468853) was used as the BSR resistance donor parent for this study. The wild species accession was collected in Texas, United States, previously characterized as highly resistant against Sclerotinia BSR disease in greenhouse tests ( Block et al, 2009 , 2010 ) and used to develop the BSR resistant introgression lines HA-BSR6, HA-BSR7 and HA-BSR8 ( Talukder et al, 2019a ). PI 468853 was crossed and backcrossed with two cultivated sunflower inbred lines, HA 89 and HA 458, to develop an AB-QTL mapping population comprised of 174 BC 2 F 4 families.…”

“…Despite reports of high levels of Sclerotinia resistance existing in the secondary gene-pool, comprehensive studies have not been pursued to characterize and exploit the resistance in practical sunflower breeding programs. Only recently, introgression and molecular mapping of Sclerotinia resistance from wild species have been reported and germplasms with introgressed resistance have been released ( Qi et al, 2016 , 2018 ; Talukder et al, 2019a , b , 2021 ). Talukder et al (2021) mapped 21 BSR resistance QTL in an advanced backcross (AB-QTL) population developed from the cross of HA 89 and an accession of the wild annual species H. argophyllus Torr.…”

Registration of Oilseed Sunflower Germplasms HA‐BSR6, HA‐BSR7, and HA‐BSR8 Highly Resistant to Sclerotinia Basal Stalk Rot and Downy Mildew

“…A whole genome scan using genotyping‐by‐sequencing technology detected alien segments of H. praecox subsp. runyonii mostly on linkage groups (LGs) 8, 10, and 11 for HA‐BSR6, LGs 1, 5, 8, 10, and 11 for HA‐BSR7, and LGs 1, 5, and 9 for HA‐BSR8 (Talukder et al, 2019). HA‐BSR6, HA‐BSR7, and HA‐BSR8 likely carry both common and unique H. praecox subsp.…”