The 2011 ASHS Annual Conference

There are more than 130 recognized species in the genus Rosa. However, only about 7-10 species of Rosa are found in the background of most modern rose cultivars. To expand the genetic background for modern roses, breeders should more extensively explore wild rose resources. A better knowledge of wild rose resources will make it possible to incorporate many valuable traits into garden rose breeding programs and to develop improved garden rose cultivars that are more broadly adapted. This research was conducted to evaluate wild rose species seedlings on horticultural traits growing under greenhouse conditions. Seeds of wild rose were stratified in a refrigerator at approximately 4° C (40° F) until seeds sprouted. Sprouted seeds were sown immediately in 18 holed sheet pots (3.5″-18 count 3″ deep) using a soilless substrate (for example, peat-based mixture or pine bark and moss based substrate). Pots were kept at room temperature (ca. 21°C, or 70°F) for two days and then transferred to the greenhouse. We treated 99 Rosa species for cold stratification. So far, however, only 26 species sprouted during the stratification process (4-6 months. We developed 235 plants from 26 species of roses. Genotypes for these 26 species vary in leaves, plant types, and thorns, indicating significant genotypic diversity. Gardeners may choose to grow thornless roses for a variety of reasons. Four thornless rose species in this collection will be our potential breeding parents for thornless rose breeding.  Roses are host to a wide range of insect and disease pests.  For most rose genotypes, aphids and black spot leaf fungus are the main pest/disease concerns. Until now, no aphid and black spot infestation have been observed in the genotypes resulting from the hybridizations in this study, but it might be still very early in this set of experiments. Infections from powdery mildew, however, have been observed in some species. This disease covers new leaves and flower buds with a distinctive white, powder-like growth.  Eight wild roses exhibit resistance to this disease. Plants will be evaluated for alkalinity tolerance and aphid resistance as more plant material is available for each of the test plants.