Euphytica 26(3): 703-708 (1977)
Breeding for improvement of flowering attributes of winterhardy Rosa kordesii Wulff hybrids
Felicitas Svejda

Abstract

The results from tetraploid hybrids of R. kordesii showed that flowering attributes can be improved by a suitable combination of modifying factors as was shown previously by investigations with diploid hybrids from R. rugosa. A longer flowering period than 7 weeks indicated always the ability for recurrent bloom in these investigations but a shorter flowering period did not always indicate non-recurrent bloom.

The offspring from the cross of the recurrent R. kordesii with the non-recurrent seedling G12 segregated into non-recurrent and recurrent types in a ratio of 3:1 for a tetrasomic inheritance, assuming a duplex segregation and complete dominance.

The flowering attributes could be improved without loss of a high level of winterhardiness.

Introduction

Recurrent flowering in roses is controlled by the recessive allele for non-recurrent flowering and it segregates in simple Mendelian ratios (SEMENIUK, 1971). A study of flowering attributes in the offspring from winterhardy and recurrent R. rugosa hybrids showed that the duration of the flowering period and flower productivity could be improved through breeding (SVEJDA, 1977). The present study analyses the flowering attributes in the offspring from winterhardy tetraploid R. kordesii hybrids and compares the results with previous results from diploid R. rugosa hybrids.

Materials and Methods

R. kordesii Wulff was used as a pistillate parent in combination with the two unnamed seedlings G12 and D08. R. kordesii is a tetraploid that arose by spontaneous chromosome duplication of the R. rugosa x R. wichuraiana hybrid 'Max Graf' (Wulff, 1951). G12 was obtained from open pollination of 'Max Graf' and a cytological examination by Dr D. R. Sampson, of this Station, found it to be tetraploid (2n = 4x = 28). G12 differs from R. kordesii in that it is very hardy at Ottawa where it shows little or no winterkill. It flowers non-recurrently and produces fewer flowers. It has single, pink flowers like 'Max Graf'. R. kordesii is regularly killed to the snow-line at Ottawa, it flowers recurrently and is more floriferous than G12. Unlike 'Max Graf, R. kordesii has double flowers.

The duration of the flowering period was determined by examining each seedling weekly in the 16 week period from June till September. The amount of bloom was estimated as of the surface area covered. The ratings of amount of bloom and % winterkill were as described previously (SVEJDA, 1977).

As in the previous study, the observations on the total seedling populations were carried out for a 2-year period. The data in Table 1 and 2 were obtained from the second year, the data in Table 3 from the average of 2 years. The observations were continued for an additional 2-year period on 6 selected seedlings from each population. The selection criteria were flowering characters, hardiness, disease resistance and appearance of flowers and shrubs.

Table 1. Flowering period, from June till September, of F1 seedlings from the crosses of (A) R. kordesii x G12 and (B) R. kordesii x DO8.

Cross Flowering in weeks
  l-6   7-16   total  
  number % number % number %
A 73 82.0 16 18.0 89 100
B 34 64.2 19 35.8 53 100

Table 2. Amount of flowers in F1 seedlings from crosses of (A) R. kordesii x G12 and (B) R. kordesii x DO8.

Cross Average amount of flowers, in % coverage, during 16 weeks from June till September
    1-5 6-12 13-25 26-50 51-75 76-100 total
A Number of
seedlings
20 35 23 8 2 1 89
  % 22.5 39.3 25.8 9.0 2.3 1.1 100
B Number of
seedlings
3 10 21 12 6 1 53
  % 5.7 18.9 39.6 22.6 11.3 1.9 100

Table 4.

Seedling Flowering period in
weeks from June till Sept.
Amount of flower in
% coverage
Winterkill in %
  mean range test1 mean range test1 mean range test1
A4 12.0 a 12 bc 11 b
A5 10.8 a 13 abc 11 b
A1 9.8 ab 17 abc 19 a
A3 6.0 c 25 ab 11 b
A6 6.0 c 9 bc 4 b
A2 5.5 c 17 abc 23 a
R. kordesii 7.3 bc 30 a 45 a
G12 5.5 c 10 bc 10 b
             
B4 12.0 l 11 m 8 m
B1 8.5 lmn 15 lm 7 m
B5 6.8 mn 13 m 11 m
B2 5.3 n 25 lm 14 m
B3 5.3 n 16 lm 5 m
B6 5.0 n 38 l 10 m
R. kordesii 7.3 lmn 30 l 45 l
DO8 10.3 lm 19 lm 14 m
1 Means followed by the same letter(s) are not significantly different at P ≤ 0.05 as determined by Duncan’s Multiple Range Test.