QTL discovery for resistance to black spot and cercospora leaf spot, and defoliation in two interconnected F1 bi-parental tetraploid garden rose populations

Jeekin Lau; Haramrit Gill; Cristiane H Taniguti; Ellen L Young; Patricia E Klein; David H Byrne; Oscar Riera-Lizarazu

doi:10.3389/fpls.2023.1209445

QTL discovery for resistance to black spot and cercospora leaf spot, and defoliation in two interconnected F1 bi-parental tetraploid garden rose populations

Front Plant Sci. 2023 Jul 27:14:1209445. doi: 10.3389/fpls.2023.1209445. eCollection 2023.

Authors

Jeekin Lau¹, Haramrit Gill¹, Cristiane H Taniguti¹, Ellen L Young¹, Patricia E Klein¹, David H Byrne¹, Oscar Riera-Lizarazu¹

Affiliation

¹ Department of Horticultural Sciences, Texas A&M University, College Station, TX, United States.

Abstract

Garden roses are an economically important horticultural crop worldwide, and two major fungal pathogens, black spot (Diplocarpon rosae F.A. Wolf) and cercospora leaf spot of rose (Rosisphaerella rosicola Pass.), affect both the health and ornamental value of the plant. Most studies on black spot disease resistance have focused on diploid germplasm, and little work has been performed on cercospora leaf spot resistance. With the use of newly developed software tools for autopolyploid genetics, two interconnected tetraploid garden rose F₁ populations (phenotyped over the course of 3 years) were used for quantitative trait locus (QTL) analysis of black spot and cercospora leaf spot resistance as well as plant defoliation. QTLs for black spot resistance were mapped to linkage groups (LGs) 1-6. QTLs for cercospora resistance and susceptibility were found in LGs 1, 4, and 5 and for defoliation in LGs 1, 3, and 5. The major locus on LG 5 for black spot resistance coincides with the previously discovered Rdr4 locus inherited from Rosa L. 'Radbrite' (Brite Eyes™), the common parent used in these mapping populations. This work is the first report of any QTL for cercospora resistance/susceptibility in tetraploid rose germplasm and the first report of defoliation QTL in roses. A major QTL for cercospora susceptibility coincides with the black spot resistance QTL on LG 5 (Rdr4). A major cercospora resistance QTL was found on LG 1. These populations provide a genetic resource that will further the knowledge base of rose genetics as more traits are studied. Studying more traits from these populations will allow for the stacking of various QTLs for desirable traits.

Keywords: Rosa; black spot; cercospora leaf spot; defoliation; quantitative trait loci.

Grants and funding

This work was supported by the Robert E. Basye Endowment in Rose Genetics and the US Department of Agriculture Specialty Crop Research Initiative projects “Combating rose rosette disease: short term and long-term approaches” (2014-51181-22644), “RosBREED: combining disease resistance with horticultural quality in new rosaceous cultivars” (2014-51181-22378), “Tools for genomics-assisted breeding polyploids: development of a community resource” (2020-51181-32156), and “Developing sustainable rose landscapes via rose rosette disease education and outreach, socioeconomic assessments and breeding RRD resistant roses with stable black spot resistance” (2022-51181-38330).