To update and complete a collection of wild roses in the Montreal Botanical Garden, Canada, in vitro embryo culture was used to propagate several Rosa species that are only available as seeds and difficult to germinate conventionally. Using embryo culture, it was possible to overcome seed dormancy and to rapidly increase the number of species in the collection, and this from a very limited number of seeds obtained from botanical institutions located around the world.
Given the regularity of periods of drought in the southwestern U.S., concern over an ample supply of high quality water is always an issue. With a diminishing water supply, higher quality water will likely be diverted to higher priority uses; therefore, concern arises over the availability and quality of water for landscape use. This project was designed to screen representative cultivars from several of the major garden rose categories (China, Tea, Polyantha, Hybrid Tea, and Found Roses) for tolerance to saline irrigation water. Roses were placed in a completely randomized design with four replications in a container holding area. Salinity treatments were designed to be a 2:1 molar ratio of NaCl:CaCl2. The treatments consisted of 0, 6.25, 12.5, 25, and 50 mmol NaCl. The volume of solution applied to each treatment was adjusted at every irrigation event to meet ET and produce a 30% leaching-fraction. At the conclusion of the study, the China rose retained the best foliage while one of the hybrid tea roses maintained flowering throughout the study at all treatment levels. It appears that the roses with the smallest leaflets were able to tolerate salinity better than those with larger leaflets. Results of the tissue sample, leachate, spad and media analyses will also be presented.
. Hill Memorial Foundation, and by the generous donation of roses from Dillon Floral Corporation, Bloomsburg, Pa. Rose plants and other materials were donated by the Conard-Pyle Co., Bear Creek Gardens, DeVore Nurseries, Inc., and Grace Sierra. The cost
Abstract
Here we report the first evidence of resistance of roses to the blackspot disease, Diplocarpon rosae Wolf. Black-spot is a major foliar disease of roses that causes severe losses to commercial and home gardeners. It spreads rapidly on susceptible cultivars, results in premature defoliation, and severely reduces yield and quality of this popular plant. Growers must make frequent applications of fungicides which are costly in labor and materials and environmentally undesirable. Stewart and Semeniuk (3) reported on the problems and techniques in transferring resistance to blackspot from the diploid species to garden roses (1, 2). The breeding lines Spotless Gold, Spotless Yellow, and Spotless Pink will be released for use as resistant parents in breeding programs. This germplasm should be valuable to breeders for its resistance to 7 isolates of D. rosae from Belts-ville, Maryland, Tifton, Georgia, Ames, Iowa, Ithaca, New York, Delaware, Ohio, University Park, Pennsylvania, and Tyler, Texas. These roses have been released by the U.S. Department of Agriculture, Science and Education Administration. The developmental work was done by the Florist and Nursery Crops Laboratory at the Agricultural Research Center, Beltsville, Maryland.
Abstract
‘Galaxie’, one of the early garden geraniums (Pelargonium X hortorum Bailey) originating from the Iowa State Univ. breeding program, was well received by both gardeners and industry because of its compact, free-flowering habit and general ease of culture. Its faults of uninteresting flower color and a tendency to injury by Botrytis cinerea Pers. and two-spotted mites were common to others of its color class; namely, ‘Penny’ (syn. ‘Penny Irene’) ‘Irvington Beauty’ (syn. ‘Rose-Pink Flat’), and ‘Pink Abundance’. The new cultivar ‘Hazel’ (Fig. 1) has the compact, floriferous plant habit of ‘Galaxie’, but improves upon its disease and mite tolerance and flower color. ‘Hazel’ is derived from a breeding program in which major stress has been placed upon developing garden geraniums capable of growing and flowering in areas subject to high summer temp at night and the high relative humidity, the usual climatic pattern in the Midwestern U.S.
Blackspot disease, caused by Diplocarpon rosae, is a devastating disease of garden roses. Most hybrid teas and floribundas are susceptible to this disease in contrast to many species roses, which are resistant. The basis of this resistance is not known. The first barrier to invasion by the pathogen is the outer surface of the leaf. The physical nature of this surface may influence the attempted infection, landing, germination and penetration by the fungal spore and may cause a failure of infection. The leaf surfaces of susceptible and resistant genotypes were observed using SEM that allowed examination of the fine structure of the leaf surface. The characteristics of the leaf surface topography including wax structures were pictorially compared and visual concepts developed in relation to the dynamic nature of the leaf surface in space and time as leaf is infected by the pathogen.
A study was conducted on the Texas A&M Univ.-Commerce campus to evaluate the effect of compost type on the spread of bermudagrass into rose garden beds. Roses were planted in an randomized complete-block design in beds amended with composts derived from yard waste, manure, poultry litter, or dairy manure, or an unamended control. The study site was free of vegetation prior to planting. No pre- or post-emergent herbicides were applied after planting. Each bed was assessed visually monthly and scored on a scale of 0 to 10, with each point equivalent to 10% coverage. A bed received a score of 10 upon full coverage. Beds amended with poultry litter and yard waste had significantly higher bermudagrass invasion and reached 100% coverage more quickly than other treatments. Some of the poultry litter beds reached 100% coverage within 40 days of planting. The control planting had significantly lower coverage than all compost treatments throughout the study.
While Japanese barberry (Berberis thunbergii) is an acknowledged invasive plant, the danger posed by its garden cultivars is unknown. This work analyzed the reproductive potential and seedling traits of wild type Japanese barberry and four important cultivars: `Atropurpurea', `Aurea', `Crimson Pygmy', and `Rose Glow'. The germination capacity of cleaned and stratified seeds was determined for all accessions in a greenhouse and seedling foliage color was noted. A subpopulation of seedlings from each accession was grown further in containers outdoors for a full season to ascertain seedling vigor. The average number of seeds produced per landscape specimen ranged from 75 and 90 for `Aurea' and `Crimson Pygmy' to 2967 for `Atropurpurea', 726 for `Rose Glow', and 1135 for wild type B. thunbergii. The vigor of 1-year seedlings—as measured by dry weight of top growth—for progeny derived from `Aurea' (2.29 g) and `Crimson Pygmy' (2.74 g) was less than `Atropurpurea' (3.45 g), `Rose Glow' (3.88 g) and wild type (3.73 g). Seedlings derived from purple-leaf cultivars displayed variable ratios of green and purple leaf phenotype correlated to the proximity and identity of likely Japanese barberry pollinators. `Rose Glow' specimens located among other purple-leaf B. thunbergii produced up to 90% purple seedlings, while other samples growing in isolation or near green-leaf plants produced less than 10% purple progeny. This suggests that some invasive green-leaf Japanese barberry could be derived from cultivars. The results also show that these cultivars express disparate reproductive potential.
Several colchicine-induced amphidiploids of blackspot-resistant, wild diploid rose species were produced for interbreeding with tetraploid garden roses. Shoot-tip chromosome counts confirmed that 86-7 (Rosa wichuraiana Crep. × R. rugosa rubra Hort.) and 86-3 (R. laevigata Michx. × R. banksiae Aiton) are amphidiploids (2n = 4x = 28), and that 84-1000 (R. roxburghii Tratt. × R. laevigata Michx.) is a mixoploid with diploid (2n = 2x = 14) and hypotetraploid (2n = 4x-1 = 27) sectors. The measured volume of pollen grains and guard cells was higher in the tetraploids. Pollen stainability was higher in amphidiploids 86-3 and 86-7 than in mixoploid 84-1000. The amphidiploid 86-7 has greater pollen fertility as determined by crossing with a range of commercial tetraploid roses than 86-3 and 84-1000, but is less fertile than its parental diploid species. Leaflets of the amphidiploids are larger and more crinkled along the midrib than in their diploid parents. These three amphidiploids provide new additions to tetraploid rose germplasm.
The feasibility of using RFLP to distinguish genetically related Hybrid Tea rose cultivars for DNA `fingerprinting' was examined with a group of cultivars related to `Peace'. The following cultivars used in this study, `Chicago Peace', `Flaming Peace', `Climbing Peace' and `Lucky Piece', were derived from bud mutations (sports) of `Peace'. We also investigated two additional cultivars, `Perfume Delight' and `Garden Party', in which one of the parents for each was `Peace'. Genomic rose DNA probes, cloned in pUC8 plasmid of Escherichia coli, were hybridized with genomic DNA of these cultivars digested with different restriction enzymes. Although polymorphisms were observed among these related cultivars, only a few probe/enzyme combinations screened produced RFLPs due to the high degree of genetic relatedness of these cultivars. We have identified probes that can distinguish all of these related rose cultivars. This study demonstrates that RFLP markers can be used effectively in DNA `fingerprinting' of genetically related rose cultivars, eventhough the level of detectable polymorphism is quite low.