background of modern varieties is relative narrow ( Liu and Liu, 2004 ; Matsumoto et al., 1998 ). The roses obtained before the breeding of ‘La France’ in 1867, the first Hybrid Tea rose, are generally called old garden roses ( Cairns, 2003 ). The beauty of
drought stress is exacerbated on plant establishment and survival, and selection of drought-tolerant plants becomes increasingly important for the development of sustainable landscapes. Roses ( Rosa × hybrid L.) are some of the most common garden plants
Overall sales of garden roses have been declining over the past 20 years in the United States due, in part, to the lack of widely adapted cultivars to heat, drought, and salt stress in landscape environments ( Byrne et al., 2010 ). Conversely, an
and leaves ( Niu et al., 2008 ). Garden rose ( Rosa spp.) is one of the most economically important and popular ornamental plants in the world. Rose has been traditionally categorized as a salt-sensitive species with salt injury reported within a
Eleven rose cultivars were field planted and evaluated weekly for disease, defoliation, and overall vigor in order to compare natural resistance to blackspot (Diplocarpon rosae). Alternative treatments were also compared for efficacy in low-maintenance disease control. Treatments included a bimonthly application of chlorothalonil, a bimonthly application of a horticultural oil, an application of chlorothalonil based on rain events, and a no-treatment control. Cultivars showed significant differences in disease severity, defoliation, and overall performance, with old garden rose varieties showing more natural disease resistance than modern susceptible varieties included in the study. Chlorothalonil applied on a 14-day spray schedule did provide a significant decrease in blackspot disease severity when compared to other treatments. A significant incidence of secondary disease including Cercospora rosicola and Botrytis cinerea occurred on old garden rose varieties. No treatment differences were found for these diseases. `Belinda's Dream', `The Fairy', and `Red Mediland' ranked highest in overall performance throughout the season.
To enlarge the palette of environmentally-responsible landscape plants, 117 garden rose cultivars were evaluated under minimal input conditions. Other than mulching and irrigation, no other inputs were provided, including no fertilization and no pesticide applications. Plants were established in completely randomized blocks with four reps in the spring of 1998 with data collection beginning in 2000 and continued through 2002. Data on overall performance (an index comprised of flower number, percent of plant covered with flowers and plant growth) and relative chlorophyll content were collected the first and third week of each month from April through October. Disease ratings or incidence ratings were collected for Diplocarpon rosae Wolf (black spot), Alternaria sp. (petal blight) and Sphaerotheca pannosa (powdery mildew). Statistical analysis was performed on the mean data for all dates. `Knockout' was the top rose for overall quality with little or no disease observed, high foliage quality, and continuous flowers from spring until late in the fall. `Knockout' also ranked among the top rose cultivars in terms of overall nutrient concentrations (N, P, K, and Fe) in new growth tissue. Most of the hybrid tea roses such as `Peace' and `Double Delight' died in at least three blocks due to disease and a lack of vigor.
Eleven rose (Rosa spp.) cultivars and advanced lines from the Morden rose breeding program were tested in controlled conditions for five components of partial resistance to two isolates of Diplocarpon rosae Wolf, the causal agent of black spot. The isolates were collected from diseased rose leaves in 1995 at Morden, Man., and in Ottawa, Ont. The components examined include incubation period (IP), leaf area with symptoms (LAS), number of lesions (NL), lesion length (LL), and sporulation capacity (SC). Differences in cultivar responses were found for all components. Of the 11 rose genotypes, no visible symptoms developed on line 91V8T201 even at 14 days after inoculation. This line was considered completely resistant to the two isolates tested. X6, T5, and `Prairie Joy' had a high level of partial resistance. N3 and `Cuthbert Grant' were intermediate. The remaining five cultivars or lines exhibited a low level of partial resistance. Linear correlations among LAS, IP, NL, and LL were high. Correlations between SC with IP, NL, or LL were nonsignificant. Although each of the five components can be used in selection for partial resistance, any one component may not represent the complete potential for a particular rose genotype. Results of this study suggest that LAS and SC are preferable as criteria for resistance to minimize the labor requirement when evaluating large numbers of rose genotypes in the greenhouse.
Rose (Rosa sp.) cultivars Blue Girl and Mister Lincoln were harvested bare-root on 1 Nov. 2001 and 22 Nov. 2002 from a commercial nursery in Arizona. Grade 1 plants were then potted and forced to flowering in either Tucson, Ariz., or Tyler, Texas. Total chilling hours were calculated as the number of hours that the plants were exposed to a temperature below 7 °C in the field and during shipping and cold storage. Data were recorded when the petals on the first flower beg an to reflex. Overall, the number of flowering shoots and plant performance was positively correlated to digging date, weeks of cold and total chilling hours received. Days from potting to flower were negatively correlated to weeks of cold storage and chilling hours. However, when the data were separated by location, the number of flowering shoots, the percentage flowering shoots, and plant performance was positively correlated to weeks of cold and chilling hours in Arizona, but was positively correlated to digging date in Texas. Days from potting to first leaf unfolding were recorded in Arizona only and were negatively correlated to weeks of cold storage and chilling hours. Days from potting to flower were negatively correlated to chilling hours at both locations and also to weeks of cold storage in Texas. The increase in chilling from two or four weeks of cold storage increased the number of flowering shoots and performance rating of plants forced in Arizona during both seasons, but only for the 2001 season in Texas. During the 2002 season in Texas, these responses were not influenced by cold storage, but were greater than those seen during the 2001 season. In Arizona, days from potting to flower were greater in 2001 than 2002, and decreased in response to cold storage in 2001, but not in 2002.
, it has spread east with the aid of Rosa multiflora , a naturalized rose species host and has become widespread from the Great Plains to the East Coast of North America ( Amrine, 2002 ). This epidemic has spread to garden roses in home and commercial
Roses are used as ornamental plants in gardens, as cut flowers, and as potted flowers but also have economic value as sources of essential oils for perfumes and cosmetics ( Yan et al., 2014 ; Zhou et al., 2020a ). The genus Rosa comprises ≈200