Rose parental characterization and population development for the identification of novel rose black spot resistance genes [abstract]

Authors: ZLESAK, DAVID - University Of Wisconsin; BRADEEN, JAMES - University Of Wisconsin; KUMMETH, SARAH - University Of Wisconsin; Bassil, Nahla; Zurn, Jason; HOKANSON, STAN - University Of Minnesota

Submitted to: International Society for Horticultural Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2017
Publication Date: 7/2/2017
Citation: Zlesak, D.C., Bradeen, J., Kummeth, S., Bassil, N.V., Zurn, J.D., Hokanson, S.C. 2017. Rose parental characterization and population development for the identification of novel rose black spot resistance genes [abstract]. International Society for Horticultural Science Meeting. July 2-7, 2017, Angers, France.

Interpretive Summary: Rose black spot is one of the most devistating disseases of cultivated roses for both the home and commercial market. The use of genetic resistance is the most economic and environmentally friendly management strategy for controling the disease. Currently, little is known about resistance found in roses and only three resistance genes have been mapped and characterized. To better characterize resistance found in six popular rose varieties, four populations were created and evaluated for resistance using 11 isolates of the black spot pathogen. Preliminary analysis suggests resistance is mediated by a single gene in each of the populations. The resistance found in the varieties 'Brite Eyes' and 'Lemmon Fizz' is broad and able to provide resistance to numerous strains of the pathogen. Future work will focus on mapping the genes found in these two parents.

Technical Abstract: Rose black spot disease, caused by the pathogen Diplocarpon rosae Wolf, is one of the most widespread and serious diseases of outdoor-grown roses worldwide. Defoliation caused by the disease compromises ornamental value, and repeated defoliation events weakens plants and can lead to plant death. Both race-specific and horizontal resistances to rose black spot have been documented in Rosa spp. and are valuable to pursue for the purpose of developing new resistant cultivars. Having molecular markers tightly linked to race-specific resistance genes is of great value to breeders for use in screening germplasm and working towards stacking multiple race-specific resistances. To date only three black spot resistance genes have been characterized, and tightly linked markers have only been reported for one gene, Rdr1. More resistance genes need to be characterized and tightly linked markers identified. Eleven races of D. rosae preserved in the international D. rosae race collection at the University of Minnesota were successfully cultured after ten years in cryopreservation and used to characterize six rose cultivars for resistance that would be used as parents (Brite EyesTM, ‘George Vancouver’, High VoltageTM, Lemon FizzTM, ‘Morden Blush’, and Yellow SubmarineTM). Four populations of at least 120 offspring were generated (High VoltageTM x Lemon FizzTM, ‘Morden Blush’ x Brite EyesTM, ‘Morden Blush’ x ‘George Vancouver’, and ‘Morden Blush’ x Yellow SubmarineTM) based on parental resistance patterns. To date, two populations (High VoltageTM x Lemon FizzTM and ‘Morden Blush’ x Brite EyesTM) have been challenged with eight and two races, respectively, using detached leaf assays. Individual seedlings of both populations were either susceptible or resistant to all races with which they were challenged and resistant:susceptible seedlings segregated 1:1. Segregation patterns are consistent with a single race-specific gene in simplex in each of the resistant parents (Brite EyesTM and Lemon FizzTM). Continued work to complete the phenotyping of all four populations is underway. The WagRhSNP Axiom® rose SNP array is being utilized to genotype the seedlings in each population in order to map the gene(s) and identify markers associated with resistance.