J. Hered. 62: 319-320. 1971
Inheritance of recurrent and non-recurrent blooming in 'Goldilocks' x Rosa wichuraiana progeny
Pete Semeniuk

The author is horticulturist in the Plant Science Research Division, Agricultural Research Service, U. S. Department of Agriculture, Beltsville, Maryland 20705.

Practically all the modern climbers and many of the hybrid polyanthas, floribundas, and hybrid tea roes are derived from R. wichuraiana Crepin. Semeniuk5 recently reported an example of monogenic inheritance of recurrent blooming in R. wichuraiana, which probably evolved from a single gene mutation of the normal wild-type condition, and suggested that the gene for nonrecurrent blooming was dominant to recurrent. He designated the recurrent bloomers as r/r and the nonrecurrent bloomers as R/-, (dominant wild type). Fisher and Morey1 reported earlier that after backcrossing a hardy species to garden roses for three generations some of the offspring were recurrent bloomers. Moore2 explained that in R. wichuraiana x ‘Goldilocks’ all seedlings in the F1 generation were nonrecurrent. (Reports in the literature on rose genetics are generally based on phenotypic results without determination of genotypic constitution.) This information and our earlier investigation of recurrent blooming provided material necessary for a precise determination of the inheritance of this character in progeny from a cross of the tetraploid recurrent blooming garden rose ‘Goldilocks’ with R. wichuraiana.

Methods and Materials

From 1964 to 1969 all selfing and crossing was carried out in a screened greenhouse. After each harvest, the seeds were after-ripened, and their seedlings grown in the greenhouse. (Seeds of rose species are dormant when mature and require a period of after-ripening at low temperatures before germination. The cold requirements were satisfied by continuous exposure to 40°F for 120 days.) Finally, root tips of all the seedlings were sampled in the manner previously described6.

Results and Discussion

Tetraploid ‘Goldilocks’ pollinated with a diploid R. wichuraiana recurrent seedling (rr) produced eight triploid recurrent bloomers (Table 1A). Apparently, the triploids arose from the union of diploid female gametes from ‘Goldilocks’ and a haploid gamete from R. wichuraiana. In order for the first generation hybrid to be recurrent, both parents had to contribute the same genes for recurrent blooming. Therefore, mutation to r in R. wichuraiana had to be at the same locus as the factor for recurrent blooming in ‘Goldilocks’.

The triploids are highly sterile, and only one of the eight plants described above produced any progeny. From selfing these triploids, two recurrent seedlings were obtained, both of which were tetraploid (Table 1C). Morey and Wessig3, Wulff7, and Rowley4 previously described how tetraploids could arise from fertile triploid roses.

Table 1. Phenotypic and genotypic constitution for the recurrent-nonrecurrent locus in triploid,
tetraploid, and pentaploid seedlings from ‘Goldilocks’ x R. wichuraiana

Crosses Genetic constitution
and phenotype
A ‘Goldilocks’ x R. wichuraiana
tetraploid x diploid
rrrr x rr
recurrent x recurrent

3n
rrr (8)
recurrent
B (‘Goldilocks’ x R. wichuraiana) x ‘Goldilocks’
triploid x tetraploid
rrr x rrrr
recurrent x recurrent

3n 4n
rrr (1) rrrr (1)
recurrent recurrent
C (‘Goldilocks’ x R. wichuraiana) self
triploid self
rrr
recurrent

4n
rrrr (4)
recurrent
D ‘Goldilocks’ x R. wichuraiana
tetraploid x diploid
rrrr x Rr
recurrent x nonrecurrent

3n 3n 5n
rrr (3) rrR (1) rrrrR (1)
recur. nonrecur. nonrecur.
E (‘Goldilocks’ x R. wichuraiana) x R. wichuraiana
triploid x diploid
rrr x Rr
recurrent x nonrecurrent

3n
Rrr (2)
nonrecurrent

The triploid recurrent F1 backcrossed to ‘Goldilocks’ produced two recurrent-bloomer seedlings, of which one was triploid, the other tetraploid (Table 1B). Evidence showed that recurrent blooming diploid, triploid, and tetraploid roses produce only one kind of germ cell or gamete. The union of any two of these would give only recurrent blooming progeny, (Table 1A-C).

‘Goldilocks’ (rrrr) crossed with heterozygous nonrecurrent R. wichuraiana seedlings (Rr) produced three recurrent and two nonrecurrent bloomers, or which four were triploid and one pentaploid. Three of the four triploids were recurrent bloomers; the remaining triploid and pentaploid were nonrecurrent, (Table 1D). The recurrent (rrr) and nonrecurrent (rrR) triploids received two r genes from their garden parent, ‘Goldilocks’. In addition, the recurrent triploid seedling received the r gene, while the nonrecurrent triploid received the dominant R gene from the heterozygous diploid parent. The pentaploid seedling (rrrrR) apparent received four r genes from ‘Goldilocks’, and one R gene from R. wichuraiana.

Recurrent triploid ‘Goldilocks’ x recurrent R. wichuraiana (rrr) crossed to diploid heterozygous nonrecurrent R. wichuraiana (Rr), produced two triploid nonrecurrent seedlings, (Table 1E). In a larger population, this cross should produce both types of seedlings in equal numbers.

This study shows that one dominant R gene produces the nonrecurrent wild type in the presence of two or four recessive r genes. This is understandable if we assume the genes act through enzymes, and that the enzymes are only needed in very small amounts. If the gene R controls the synthesis of, or the activity of, an enzyme, one R gene can supply sufficient enzyme to produce the nonrecurrent phenotype in the presence of any number of recessive alleles.

Summary

Recurrent blooming diploid, triploid, and tetraploid roses produce germ cells or gametes containing only the recessive allele, r. Heterozygous nonrecurrent blooming diploid, triploid, and pentaploid plants produce two kinds of germ cells, those with and those without the R allele. One dominant R gene supplies sufficient enzyme to produce the nonrecurrent wild-type phenotype in the presence of 1, 2, or even 4 recessive r alleles.

Literature Cited

  1. Fisher, R. C. and D. H. Morey. The rose gene pool. Am. Rose Ann. 48: 160-165. 1963.
  2. Moore, R. S. A study of moss and miniature roses. Am. Rose Ann. 53: 49-60. 1968.
  3. Morey, D. H. and A. Wessig. Chromosome numbers in Rosa. Am. Rose Ann. 38: 107-110. 1953.
  4. Rowley, F. D. Triploid garden roses. Am. Rose Ann. 45: 108-113. 1960.
  5. Semeniuk, P. Inheritance of recurrent blooming in Rosa wichuraiana. J. Hered. 62: 203-204. 1971
  6. ————— and T. Arisumi. Colchicine induced tetraploid and cytochimeral roses. Bot. Gaz. 129: 190-193. 1968.
  7. Wulff, H. D. Cytology of two fertile triploid roses. Am. Rose Ann. 44: 118-120. 1959.

CybeRose note: It is commonly assumed that triploids are necessarily sterile. The above report, and the item below, suggest that some triploids are not only fertile, but capable of crossing with other species even though the diploid form will not.

University of California publications in agricultural sciences, 2(14): 376-400
Studies on Polyploidy. I. Cytological Investigations on Triploidy in Crepis
M. Navashin
p. 382
The triploid plants of C. capillaris were finally crossed by Miss Gerassimova with normal plants of various other Crepis species; primarily in the hope of determining the constitution of their gametes, and also in order to test their crossability, which might differ from that of normal plants. The majority of interspecific hybrids obtained from the application of the foreign pollen to the stigmas of the the triploids proved upon examination to contain a diploid chromosome complex of C. capillaris together with a haploid chromosome group of the other species used as the male parent; moreover, viable hybrids were obtained from crosses which had never been successful when diploid C. capillaris plants were used for crossing. Thus a hybrid between C. capillaris and C. alpina was obtained, a cross which had never been secured before. It has thus been shown that a triploid plant undergoes interspecific hybridization more readily than a diploid one. Finally, a hybrid plant was obtained which possessed four haploid chromosome complexes of C. capillaris and one of another species (C. neglecta). This demonstrates that triploids may produce viable tetraploid eggs in addition to haploid and diploid ones. These polyploid hybrids of various kinds proved to be much more fertile than the common diploid ones.