Anomalous Inheritance in Rosa rugosa
David Austin's English Roses (1993) p. 28
The third line we pursued was by way of the Rugosa hybrid 'Conrad Ferdinand Meyer.' At first we harbored no great hopes of success, for we feared that the resulting seedlings from a cross with this excessively vigorous hybrid would be altogether too gross in character. 'Conrad Ferdinand Meyer' was itself a cross between the very popular and beautiful Climbing Noisette Rose 'Gloire de Dijon,' and an unknown Rugosa hybrid. It also had one of the most powerful and delicious fragrances. As before, we crossed with some of our better English Rose in particular 'Chaucer,' and had one of those pieces of luck that sometimes turn up in rose breeding. Some of the seedlings from this cross were of typical rugosa appearance, while others bore absolutely no resemblance to a Rugosa Rose. It seemed that some of our hybrids had taken the genes only from the 'Gloire de Dijon' half of 'Conrad Ferdinand Meyer,' while others had inherited those from the Rugosa side. What we had in many instances were in effect hybrids of 'Gloire de Dijon.'
A further rugosa-cross remains (1934:4). Here the situation is more complex, since one specimen shows no signs of the father, but yet without being maternal, and since the other specimen is probably a true hybrid with a great prevalence of the mother's characters. The former is entirely sterile in 1941, no hips being formed, although it flowered abundantly. The latter plant agrees in respect to sterility, hip-properties and content of ascorbic acid with the canina-rugosa hybrids mentioned previously. Cytological studies as well as progeny controls will at once elucidate the state of things.
R. canina II x rugosa: 1934-4 This series consists of two individuals. One is a monosomic plant showing almost no trace of the father but also being very unlike the mother. It is smaller and less vigorous than its sister-plant, having few and rather weak prickles, small purely white petals, a light-green colour on stem and leaves, and lacks anthocyanin. It is less winter-hardy than its sister-plant; during the cold winters 1941 and 1942 the superterrestrial parts were entirely killed. It cannot be a monosomic of the mother-plant since the meiotic behaviour is that typical of canina-rugosa hybrids. Therefore in this case the loss of one chromosome obliterates the characters brought in by the rugosa genome.
CybeRose note: this specimen is particularly interesting in regards to Hurst's "Septet Theory". Apparently the sectional characters are linked to a single chromosomeand presumably only a portion of onerather than distributed among the set of seven chromosomes. A "Supergene Theory" could replace Hurst's early effort, and duplicate most of the behaviors and predictions.
Rowley also studied aneuploidy in roses (Journ of Genetics, 57. 1960-61), and mentioned Gustafsson's specimen. However, most of the aneuploids discussed differed little from expectation. Which is to say that the seven chromosomes of the basic set are not equal in their effects on the plant.
A Rose Odyssey (1937: p123-124)
J H Nicolas
In 1933 I had found a curious sport on Margaret McGredy. The foliage strongly resembled Rugosa but the plant characteristics also leaned toward R. cinnamomea. I mentioned this fact to Sam III [McGredy] when I visited him in 1934. Sam could not account for the sport. He had never used species in his breeding. His brother-in-law, Walter I. Johnston, spoke up, "Your father did much more work with species." We adjourned to the office, where complete hybridizing records from the early days of the firm are kept, one volume for each year, a valuable library. After several hours of research we traced the origin of Margaret McGredy to crosses of Rugosa and Cinnamomea. They were, of course, many generations back. But as these two species are in the blood stream of Margaret McGredy and all modern McGredy roses, the possibility of the sport was explained. It is an accepted fact that hybrids alone sport (pure species mutate, but rarely, if ever, sport) and can sport only within what is in them.*
Lately, the most unusual thing has happened to that sport. A sport is supposed to be a part of the hybrid compound which "took a walk". But this sport must have carried the whole pack as it has sported again a Hybrid Tea type with a magnificent bloom much more intensely colored than the original Margaret McGredy and is a distinctly a different rose. I am planning to name it "Margaret Second".
*A mutation is a significant change in form or character occurring suddenly in a single generation. H. de Vries defines it: "A permanent transmissible variation in organisms, as distinguished from a sport." A sport is a change in some part of a plant due to disturbance or dissociation of the compound of a hybrid. A sport character is seldom transmissible.
American Rose Annual 41: 123-125 (1956)
New Approach To The Breeding Of Hardy Roses
Dr. F. L. Skinner
Under label Iowa #9 I received from Professor Buck a semi-double white rose resembling a Rugosa but which I am told has no Rugosa in its pedigree;
CybeRose note: These surprizing results in Rosa rugosa hybrids inform us that there is more to heredity than Mendel conceived. Where Gustafsson found the influence of Rugosa to be dominant, and associated with a single chromosome, Nicolas's account reveals that the distinctive character of Rugosa's leaves can lie dormant for several generations, awaken briefly in a sport, then again disappear in a subsequent sport.