|TALUKDER, ZAHIRUL - North Dakota State University|
|LONG, YUNMING - North Dakota State University|
Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2019
Publication Date: 3/1/2019
Citation: Talukder, Z.I., Long, Y., Seiler, G.J., Underwood, W., Qi, L. 2019. Introgression and monitoring of wild Helianthus praecox alien segments associated with Sclerotinia basal stalk rot resistance in sunflower using genotyping-by sequencing. PLoS One. 14(3):e0213065. https://doi.org/10.1371/journal.pone.0213065.
Interpretive Summary: Diseases are considered the yield-limiting factor in sunflower production. Three diseases resulting from Sclerotinia (also known as white mold) infection are major problems for sunflower producers worldwide. Among them, basal stalk rot (BSR) is the most prevalent disease in humid temperate, as well as tropical and sub-tropical regions of the world. Due to limited chemical and biological controls for BSR and a lack of sufficient resistance in present-day hybrids, identification of new sources of resistance is needed. Because resistance in the cultivated sunflower gene-pool is insufficient to combat BSR, new sources of resistance from the vast sunflower crop wild relative’s pool are being explored. One sunflower crop wild relative, the Texas sunflower (Helianthus praecox), was discovered to be highly resistant to BSR disease and this resistance trait was transferred into cultivated sunflower. Eight germplasm lines were developed with significantly increased resistance to BSR. Molecular techniques confirmed that the genomic segments of the wild species providing the resistance trait were successfully transferred to the cultivated sunflower. Four of these lines also possessed resistance against sunflower downy mildew, another serious disease of sunflower. Stacking these resistance genes for sunflower diseases will provide a valuable genetic resource for sunflower breeders to provide more efficient, durable, and environmentally friendly approaches for sustaining sunflower as an economically viable crop.
Technical Abstract: Sclerotinia basal stalk rot (BSR), caused by the necrotrophic fungus Sclerotinia sclerotiorum, is a major disease that affects sunflowers (Helianthus annuus L.) worldwide. Breeding for BSR resistance traditionally relies upon cultivated sunflower germplasm that has only partial resistance thus lacking an effective resistance against the pathogen. Introgression of BSR resistance from wild Helianthus species has promise for the genetic improvement of cultivated sunflower. In this study, we successfully transferred BSR resistance from an annual crop wild relative, Helianthus praecox, into cultivated sunflower and assessed the introgressed alien segments associated with BSR resistance using the genotyping-by-sequencing (GBS) approach. Crosses were made between the nuclear male sterile HA 89 and highly BSR resistant H. praecox accessions. The resistant F1 plants were selected and backcrossed to HA 458 and HA 89. Progenies at early generations (F1 to BC2F2) were evaluated for BSR resistance under high disease pressure in the greenhouse, while the BC2F3 and subsequent generations were evaluated in the inoculated field nurseries in multiple environments. Eight highly BSR-resistant H. praecox introgression lines were selected across seven environments from 2012 to 2015 in North Dakota and Minnesota, USA. The mean BSR disease incidence (DI) for H.pra 1 to H.pra 8 ranged from 1.2 to 11.1%, while DI of Cargill 270 (susceptible hybrid), HA 89 (recurrent parent), HA 441 (resistant inbred), and Croplan 305 (resistant hybrid) was 36.1, 31.0, 19.5, and 11.6%, respectively. Molecular assessment using GBS revealed the presence of H. praecox segments in linkage groups (LGs) 1, 8, 10, 11, and 14 of the introgression lines. Both shared and unique polymorphic SNP loci were detected throughout the entire genomes of the introgression lines, 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, Pl17, derived from the HA 458 parent was present in four introgression lines. Introgression germplasms combining Sclerotinia BSR and DM resistance will extend the useful diversity of the primary gene pool in the fight against two destructive sunflower diseases.