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U.S. black raspberry (BR) production is currently limited by narrowly adapted, elite germplasm. Improved understanding of genetic control and genotype-by-environment interactions (GEI) of pomological traits will inform the development of improved BR germplasm and cultivars. To this end, analysis of a multi-environment trial of two BR mapping populations derived from crosses of commercial cultivars with wild accessions is providing insights into genetic variation, quantitative trait loci (QTL), and GEI related to traits of horticultural value. Twenty-six horticultural and fruit quality traits were evaluated in two mapping populations over three years at four distinct locations representative of current U.S. BR production. One fruit quality trait, drupelet count, has been analyzed, and nine additional fruit quality traits are being analyzed. Random factor analysis of genetic effect was used to account for missing data. GEI analysis was performed using a Bayesian approach to Finlay-Wilkinson regression and genotyping-by-sequencing (GBS)-derived genomic relationship matrices, with the purpose of verifying relatedness and identifying genotypes with stable performance over environments. Genetic maps were reconstructed using GBS-derived markers and the latest genome assembly for BR. Among relevant results, pedigree verification led to construction of reliable linkage maps, and a QTL spanning a one to five megabase region containing several hundred genes was identified on chromosome 1. This region has a stable influence over drupelet count over environments (location by year). These and related findings are expected to guide further genetic characterization of BR fruit quality, management of breeding germplasm, and development of improved BR cultivars for U.S. production.

Over the last 75 years, the black raspberry industry in the United States has steadily declined due to lack of adapted and disease resistant cultivars. The high anthocyanin content of black raspberry and associated health benefits have revived interest in production and breeding new cultivars. The United States Department of Agriculture (USDA) Agricultural Research Service, National Clonal Germplasm Repository manages black raspberry germplasm and maintains a collection of over 175 accessions. Wild black raspberries collected in their native range from more than 130 locations across 27 US states and two Canadian provinces were recently added to this collection. Evaluation of this wild germplasm led to the identification of four sources of aphid resistance, two of which were introgressed into the elite breeding pool in two mapping populations. A major focus of this project is to develop, and make available, genomic tools including linkage and physical maps, a draft genome assembly, ESTs, SNP and SSR markers for use in black and red raspberry breeding. We will study genotype by environment interactions in this black raspberry germplasm in four different production regions across North America and apply the genomic tools to identify QTL important for breeding objectives. These tools will facilitate informed decisions regarding germplasm value and usage, crossing, and selection through marker-assisted breeding, and will be useful for breeding programs across the US. Here, we present the current status of global genetic resources and genomic research in black raspberry.

29th International Horticultural Congress on Horticulture - Sustaining Lives, Livelihoods and Landscapes (IHC) / 2nd International Berry Fruit Symposium - Interactions! Local and Global Berry Research and Innovation -- AUG 17-22, 2014 -- Brisbane, AUSTRALIA, WOS: 000391239600005, Over the last 75 years, the black raspberry industry in the United States has undergone a slow but steady contraction because of a lack of adapted, disease resistant cultivars. Recent research about the health benefits of a diet rich in polyphenolics, from black raspberries in particular, has led to a resurgence of interest in this fruit and a renewal of breeding efforts. This study seeks to advance and streamline identification of a variety of traits of interest to growers and consumers in black raspberry germplasm through phenotyping and socio-economic analyses. The information will be integrated into breeding programs with the goal of developing disease resistant cultivars that satisfy the demands of the marketplace, adding to the sustainability and profitability of the industry. Two related full-sib populations, designated ORUS 4304 (192 progeny) and ORUS 4305 (115 progeny), were planted across the production regions. Primocane (non-fruiting canes) vigor was rated from 1 (dead) to 9 (very vigorous) at each site. Initial analysis of genotype by environment (GxE) influences on primocane vigor indicated that overall the populations showed no significant difference in vigor in different environments; however, individual genotypes showed significant variation depending on site conditions. Vigor data will be compared with the genetic linkage map to determine which genomic regions contribute to the control of this complex trait. The genomic tools we are developing will be applied to the identification of quantitative trait loci (QTL) and alleles important for breeding objectives regionally and nationally., Int Soc Hort Sci

Lack of variation among black raspberry cultivars is thought to be a limiting factor in fruit production and in breeding improved cultivars. An assessment of the available diversity in black raspberry is needed to effectively develop improved cultivars. Such an assessment was done to estimate the genetic similarities for RAPD markers in 16 black raspberry genotypes and to determine the genetic diversity among these genotypes based on these markers. In addition, the ability to distinguish between the black raspberry genotypes, two red raspberry cultivars (Rubus idaeus L.), and a blackberry cultivar (Rubus hybrid) was determined. A similarity matrix from 379 RAPD markers was calculated, and a phylogenetic tree was constructed using the PHYLIP suite of phylogeny software, which revealed the relationship among the genotypes. An average of 81% similarity was calculated among 16 black raspberry genotypes with a maximum similarity of 98% and a minimum of 70%. The average similarity between black raspberry and red raspberry was 41% and was 26% between black raspberry and blackberry. Combined marker profiles from six RAPD primers could be used to distinguish between the 16 black raspberry genotypes. Red raspberry and blackberry could be distinguished from black raspberry by 27 and 29 of 30 RAPD primers tested, respectively. Genetic diversity was most prominent in genotypes from the extremes of the black raspberry indigenous range. Diversifying the germplasm pool for black raspberry cultivar improvement can be achieved through utilizing genotypes from the extremes of the black raspberry range and through interspecific hybridization.

A partial diallel design was used to investigate the inheritance of tolerance to terbacil herbicide in cultivated strawberry, Fragaria ×ananassa Duch. Two tolerant cultivars, `Honeoye' and `Earliglow', two moderately tolerant cultivars, `Lester' and `Allstar', and two susceptible cultivars, `Red Chief' and `Guardian' were used as parents to create populations that segregated for tolerance to the herbicide. Tolerance rankings of the populations closely coincided with expected rankings based on the published tolerance levels of parental cultivars. `Honeoye' and `Earliglow' derived populations had the highest average tolerance ratings, while `Guardian' derived populations had the lowest tolerance ratings. Heritability was estimated at h2 = 0.50, indicating that significant progress in increasing the tolerance of new cultivars to terbacil can be achieved through traditional recurrent selection procedures. General and specific combining abilities suggest that the tolerant cultivars in this study may be fixed in their tolerance and that increased mean tolerance will be most apparent in progenies combining tolerant and susceptible cultivars. As such, a broader pool of germplasm may be needed to develop cultivars that are more tolerant than those in this study. Chemical names: terbacil (3-tert-butyl-5-chloro-6-methyluracil)