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.
Europe and China. Gardeners grew them to meet practical needs such as for oils and medicine ( Widrlecher, 1981 ), but the rose flower also is considered so beautiful that it has been regularly mentioned in poetry, religion, and represented in art and
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
, public parks, commercial spaces, and residential areas. Garden roses provide aesthetic value throughout the growing season due to both their vegetative and floral production. Plant architecture of roses is linked to flower yield and ornamental value
, 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
in the Purdue Horticultural Gardens, West Lafayette, IN. The rose cultivars examined were Rosa-hybrid ‘Purple Passion’, ‘Garden Party’, ‘Mister Lincoln’, ‘Knockout’, and Rosa foetida ‘Bicolor’ (syn. ‘Austrian Copper’). These cultivars were chosen
Roses, which are distributed throughout the temperate regions of the Northern Hemisphere ( Krüssmann, 1981 ), have been important ornamental plants for more than 5000 years. There are thousands of cultivars for the garden, floriculture, medicinal
are classified into two major groups: old garden (OGR), defined as horticultural classes and cultivars present before 1867; and modern roses (MR) which are the horticultural classes and cultivars developed after 1867. Numerous cultivars of OGR perform