HortScience 15(2): 205-206. 1980
RSM K1 and RSM K5 Rose Germplasm1
H. H. Marshall
Agriculture Canada, Research Station,
Morden, Manitoba, Canada R0G 1J0

1 Received for publication March 5, 1979. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper must therefore be hereby marked advertisement solely to indicate this fact.

The improvement of winter hardiness of tender tetraploid hybrid tea, grandiflora and floribunda roses has been difficult because of interspecific crossing barriers between these and hardy northern species.

In the rose breeding program at Morden, the hardy tetraploid R. arkansana Porter has been crossed with the floribunda 'Donald Prior' and a few fertile F1 hybrids have been produced. These have served in breeding a new series of roses at Morden (1). Other hardy species such as R. rugosa Thunb. are diploid and produce mostly sterile triploids when crossed with tetraploid garden roses.

This paper reports a new hybrid from hardy roses which has shown cross compatibility with a wide range of roses.

Origin

Two seedlings, RSM K1 and RSM K5 (Research Station, Morden plus a code number), were found among ill seedlings in one progeny of R. rugosa 'Alba' having ('J. W. Fargo' x ('Donald Prior' x R. arkansana)] x mixed R. arkansana hybrids as a pollen parent. Since 'J. W. Fargo' is double form of R. arkansana the pollen parent carries and exhibits many characters of this species plus a slight infusion of floribunda characters. The progeny from which RSM K1 and RSM K5 were selected was vigorous and the growth habit and dark red-purple flowers of the pollen parent were predominant.

The 2 similar and fertile RSM K1 and RSM K5 seedlings exhibited the rough foliage of R. rugosa to a greater degree than their sterile, probably triploid sisters, Pollen and stomata of the fertile seedlings were of the size found in tetraploid roses; cytological examination at meiosis confirmed a tetraploid count of 28 chromosomes in RSM K1. This strongly suggests they arose from ovules with the 2n complement of R. rugosa.

Since the 2 seedlings are similar except for petal number, only RSM K1 is described.

Fig. 1-3. Flowers and foliage of R. rugosa 'Alba', hybrid RSM K1, and complex R. arkansana hybrid parent, respectively.

 

Fig. 4. Fruit of R. rugosa 'Alba' (left), hybrid RSM K1 (center) and complex R. arkansana hybrid parent (right).

Description

Shrub to 2 m high with a few long rhizomes; canes strong, tomentulose with many straight 2-10 mm prickles below becoming scattered above; petioles and lower surface of upwardly dilated stipules tomentulose; leaflets usually 7 sublustrous and lightly rugose above, pale tomentulose and moderately reticulate beneath, 3-5 cm long, eliptic to obovate, margin toothed; pedicels and base of receptacle glandular hirsute; flowers 3-15 in corymbs or singly from mid-summer to fall, 6-10 cm diameter with 5-9 petals, strong purplish red (Nickerson 10RP4-5/12), due to equal amounts of cyanin and peonin pigments; calyx reflexed on flowers, spreading on fruit, glandular hirsute without, pubescent within; fruit subglobose smooth red 1.5 to 2.5 cm in diameter; achenes 3-5 mm long.

Seedlings RSM K1 and RSM K5 have been fully winter hardy at Morden since 1975, have not been seriously affected by rust and have shown resistance to mildew and black spot. Like their parents they bloom from midsummer to fall.

RSM K1 and RSM K5 were used as pollen parents in 55 combinations and as seed parents with 22 cultivars in crosses made from 1977 to 1979. They showed a high degree of cross compatibility and produced over 8000 seeds. Seedlings from some of these crosses produced more than 2000 seeds from controlled pollinations in 1979.

RSM K1 is a fertile, compatible, hardy, long blooming tetraploid which should be valuable in developing more attractive hardy roses.

Availability

Rose breeders may obtain limited quantities of budwood, seeds or pollen upon written request.

Literature Cited

1. Marshall, H. H. 1977. New rose series meets demand. Canada Agr. 22(3): 24-26.