Delayed Fertility in Hybrids, Polyploids and Mutants

Bailey: Plant-Breeding (1897)
Quoting Focke, Pflanzen-Mischlinge:
p. 231: In a hybrid Sinningia, the pollen of the second year of flowering was better than that of the first.
p. 234: In longer-lived plants, often all the flowers of the first years are sterile, while later, when the plant has reached a certain age, a few fruits are formed; this has been noticed, for example, in Rubus Idaeus x caesius, R. Bellardii x caesius, Calceolaria integrifolia x plantaginea, Crinum Capense x scabrum.

Walker: Hybrid between Rose Geranium and Pelargonium (1885)
I was more successful with the other, from increased care, and more vigor in the plant. After a few weeks it grew vigorously and the leaves still retained the indications of being a hybrid; they had the lobed and jagged leaves of the Rose Geranium and the crispness of the Pelargonium; but the leaves were distinct from either. I propagated several plants to guard against losing the stock. I waited almost impatiently for them to flower, but, after some time, it began to seem to me as if they were intending to consult their own pleasure in this matter.
    I have waited three years. A few days since they came in bloom and most profusely. They prove to be genuine hybrids (cross between species). The flowers are midway in size between the flowers of the Rose Geranium and Pelargonium; they have the rose color that belongs to both parents but inclining to the silvery rose color of the Lady Washington Pelargonium, while all the petals are stained with the rich dark maroon that enriches the beauty of the petals of the Pelargonium. I hope to make it the basis of a class of larger-flowering Rose Geraniums.

Jour. Roy. Hort. Soc. p. lxxviii (1907)
Seedling of Delphinium Belladonna.—Mr. Sutton also showed flowers of some seedlings raised from seed produced by Delphinium Belladonna last year. This has not been known to produce seeds, at least since 1867, when the first record of the plant seems to have been made. A few seeds had been produced in the previous year, but none of these had proved fertile. The flowers of some of the seedlings resembled D. Belladonna very closely, but some more nearly approached D. formosum, and one bore flowers of a very beautiful deep blue tint.

Jour. Roy. Hort. Soc. London 2: 86-87 (1847)
Herbert: XI - On Hybridization amongst Vegetables pt. 2
I formerly mentioned that the result from the impregnation of the shrubby Calceolaria integrifolia by Calceolaria plantaginea, which is quite as humble and herbaceous as a plantain, was remarkable, the whole produce having a similar aspect, that of a very dwarf plant, with long serrated leaves on very short stiff branches, the inflorescence being exactly intermediate between that of the two species. It appeared at first to be sterile, but last year I obtained a pod from it, and it has reproduced itself as perfectly as if it were a natural species from the mountains of Chili; set with the pollen of other hybrids it has produced handsome varieties perfectly herbaceous. The whole produce of the pod I have mentioned having been similar to the parent plant, and quite distinct in appearance from any other Calceolaria, there can be no doubt that, if they were planted in a wild spot, of which the soil, circumstances, and climate suited their growth and fructification, a new species, according to the terms and acceptation of botanists, would have been there established; and yet any person who cultivated Calceolaria integrifolia by impregnating it with C. plantaginea would obtain the like.

Amaryllidaceae, p. 374 (1837)
William Herbert
I have already mentioned that Crinum scabro-capense, though the pollen of different species was applied to it had continued about sixteen years perfectly sterile. In 1834 a plant of it which had been growing the greater part of that time out of doors in front of the stove, produced one small seed. It vegetated, but the leaf was from the first of a yellowish white, and the plant did not live many weeks. In 1835 it produced another and larger seed, the early part of that summer having been very hot both those seasons. This seed was sown in white sand to try to save it from perishing like the former, and a thriving young plant has been obtained from it. Whether they are the produce of its own pollen, or that of Pedunculato-capense, which grew beside it, cannot yet be judged with certainty; but the seedling now growing vigorously, has deep green leaves, and does not shew any approximation to the glaucous hue of C. Capense, of which a large bed was not far off; and that hue would probably have been very apparent, if it had been so crossed again.
[CybeRose note: Crinum capense Herb. = C. longifolium]

Beaton: Bedding Geraniums (1852)
The cause of barrenness in geraniums is more mysterious than that in any other family of plants that I have tried. I never met a single instance in the whole race in which the female organs were not quite perfect, as far as could be made out even by the help of magnifiers. The male organs, on the other hand, have all kinds of defects, from a barren anther to the want of any traces of their existence beyond a toothed ring where they ought to spring from. Their numbers, when they are developed, are as variable as the colour of the flowers. Another freak worthy of notice, and one which ought to save a promising seedling, is that for some years a seedling may be quite destitute of pollen, and yet turn round after a while and produce pollen in abundance. Witness Compactum, in which, at first, you could not meet with a pollen anther in a hundred flowers, but now it is as rare to find a barren anther. The same with Tom Thumb. I recollect Mr. Ayres, who first brought Tom into notice, being quite fierce with some one who offered seeds of it for sale; he said the thing was downright imposition, that he had known it for so long a time, and that it produced no seeds at all. Meantime, however, Tom was getting up to the age of manhood, and thenceforward has seeded as freely as any of them.

Yearbook of Department of Agriculture for 1897
Hybrids and Their Utilization in Plant Breeding
Walter T. Swingle and Herbert J. Webber
Naudin gave many instances where, in addition to the hybrid intermediate in character between the parents, a number were obtained exactly resembling the mother species. In one case where he crossed two thorn apples (Datura stramonium with pollen of D. ceratocaula), the capsule thus fertilized remained very small and produced but few seeds, of which many were imperfect and almost all failed to germinate the next spring. Of about sixty apparently good seeds, only three grew, and from these two plants were grown to maturity. These plants were exactly like the mother plant, but were nevertheless abnormal, because of their unusual height, being nearly twice that of the mother species, and also in dropping all the flowers produced in the lower forks. Such increased vigor and partial sterility were observed by Naudin in all intermediate hybrids of Datura, but in this case the plant resulting from the cross showed no trace of the characters of the father species, and its seeds, when planted the following year, yielded the ordinary form of the mother plant.

Orchid Lily and others
Ivan Michurin
I shall cite an example of an interspecific hybrid between the yellow lily (Lilium Szovitsianum Hort.) and the red (Lilium Thunbergianum Roezl. & Schult.). The hybrid which I named the Fialkovaya Lilia [Orchid Lily] because of its beautiful purple flowers and its orchidlike scent during the first two years of blossoming failed to produce seed balls; on the third and fourth years seed balls appeared, but with empty seeds which of course failed to germinate. Only in the seventh year did the plants begin to produce seeds that would partly germinate.
[CybeRose note: I take it that the delayed fertility occurred in the F1 hybrid.]
    The same was observed when planting the seeds of a black hybrid mountain ash, obtained from the cross of Sorbus melanocarpa ♂ X Sorbus aucuparia L. ♀. For seven-eight years from about a thousand seeds of this hybrid only one or two seedlings would arise; but in 1921 mass germination was suddenly obtained. Among the seedlings quite a number considerably varied in structure.
    Furthermore, the same may be said of the vegetative hybrid between an apple and a pear; as a result an excellent new variety of apple was obtained which I named Reinette Bergamotte.
    Then again, in some cases the sterility of certain hybrids was eliminated. Thus, the hybrid between Prunus Padus Maackii X Prunus Cerasus blossomed but failed to fruit. When it was budded on to a sweet cherry stock with the aim of augmenting its vigour under the influence of the stock—the supplying of a mentor as I call it—on the following year all the flowers of the grafts set fruit which developed completely. In general, even most of the simple hybrids fail to set fruit at their first blossoming, and even if fruit are formed their seeds sometimes fail to germinate; only in the years that follow do these shortcomings in development gradually disappear!

J. Genet. 48: 80-98. (1947)
Heterochromatization as a change of chromosome cycle
Alexandra A. Prokofyeva-Belgovskaya
(5) The influence of parental age
It was found that the ageing of the parents causes a progressive heterochromatization in their progeny of the most sensitive inert regions and of the active ones in their vicinity. There is reason to suppose that ageing causes a progressive heterochromatization of the cell nuclei in the parents, and that this process tells upon the condition of the most sensitive regions in their progeny. A comparison of this evidence with that on the influence of age on crossing-over leads to the belief that the two phenomena are parallel. Ageing is accompanied by a reduction of the capacity of the chromosomes for conjugation and by a drop in the percentage of crossing-over.

Acta Horti Bergiani, Band 17, N:o 9 (1958) (1958)
Hip and Seed Formation In Newly Formed Rosa Polyploids
Folke Fagerlind
The Rosa rugosa doublings of the year 1942 formed hips and seed only in the years 1954 and 1956. This notwithstanding, the flowering was of normal extent during a succession of years before 1954 and in the year 1955. If the culture series had only comprised these doublings I should undoubtedly have drawn a conclusion that the differences in the different years were conditioned by climatological factors. The summers of 1954 and 1956 had more rainfall than 1955 and the years immediately preceding 1954. The rugosa doublings of the years 1947, 1948 and 1950 showed, however, a total absence of capacity to form hips in 1954 and 1956 as well as in the intermediate year and the preceding years. The same was also observable in all the doubled rugosa hybrids. Thus climatological differences can not, or at least not alone, explain the facts in question. The doublings representing the different year-classes have throughout been cultivated under similar conditions in the Hortus Bergianus. Only a few steps separate the rugosa doublings of 1942 from several of the younger doublings. It therefore seems quite improbable that the differences in reaction emerging in 1954 and 1956 on comparison between the doublings of different years are conditioned by variations in the external milieu.

B. The literature contains a few descriptions of phenomena which in a way seem to constitute parallels to the demonstrated rugosa doublings of which an account has been given above. SCHLÖSSER (1934) speaks of a gradual, time-consuming stabilization in a 52-chromosome clone of tomatoes. The clone derived from a newly formed (4n+4)-plant among 4n-siblings. This diverged from its sisters in a striking way. The latter showed normal fruit-forming properties. The diverging plant shed its flower-buds when these had attained an approximate length of 3 mm. It was reproduced by means of top-cutting for 9 generations. Each generation required a period of 2.5-3 months. With each generation the bud-shedding tendency was reduced. In the fourth generation, "kam es fast zur Anthese bei einigen Knospen, doch wurden sie aus inneren Gründen im letzten Augenblick abgestossen". [it came almost to the anthesis with some buds, but from internal reasons in the last instant it was pushed off.] In the sixth generation fully developed flowers appeared. In the fifth generation the buds contained lethal pollen in 80 per cent of the cases, but in the seventh the figure had sunk to 35 per cent, a feature thought to be due to changed chromosome distribution during the meiosis. The majority of PMC were believed to distribute the chromosomes in such a way that 24 went to the one and 24 to the other pole, while the 4 surplus ones remained lying in the plane of division. In the ninth generation fructification occurred. The fruits often showed a normal amount of seed. The F1-plants that were pulled up proved to be tetraploid. Control analysis showed that the members of the clonic chain of generations had the whole time possessed the chromosome number (4n+4).

WETTSTEIN (1937) has made an extremely interesting analysis of chromosome-doubled Bryum caespiticium. In contradistinction to the original plant, the doubling was androgynous. Only in exceptional cases did it form more developed sprophytes and sporangia. The latter contained an extremely uneven spore-mass. From spores in one sporangium was reared in 1926 a progeny of 100 individuals. Of these, 22 died early; 63, of which one was called Cae 220, coincided on the whole with the doubled mother-plant, and was, like the latter, diploid. The other individuals were dioecious haploids or diploids. Cae 220 formed sporophytes during the first years, but these died at an early embryonal stage. In the succeeding years there was a gradual increase in the sporophytes' capacity for development. Little by little there appeared more and more capsules with the capacity to develop to maturity. In 1937 such good fertility properties were shown that the type manifested itself as a new species. The spore formation was so even that one could now count on the meiosis running a completely normal course. The restoration of normal fertility ran parallel with the successive elimination of the gigas properties. The new species was therefore very similar to Bryum caespiticium, but differed from this through the doubled chromosome number and the androgyny. It was given the name Bryum Corrensii. Later, this plant—i.e. chromosome-doubled, androgynous Bryum caespiticium—was found in nature.
    The transformation, which was concluded after 11 years with the establishment of Bryum Corrensii, took place not only in the original Cae 220-individual, but also within a clonic series reproduced 8 times, as well as in series of plants which on one and three occasions respectively were reproduced with the help of spores occasionally formed in the course of the said period.

The Gardeners' Chronicle (Feb 11, 1928)
Bigeneric Hybrids Among the Amaryllideae
Arthington Worsley
In a new bigeneric hybrid, maturity in an individual plant is not necessarily the same thing as sexual maturity in the group. We have had many cases in which the earliest hybrids to flower were listed as sterile, but, after years had passed, the hybrid was found to be fertile. This has been the case both with the Brunsdonnas and with Ismene festalis, and also, I understand, with the Zephyranthes x Cooperia hybrids.

American Peony Society bulletin no 84: 3-12 (Sept 1941)
Some Hybrid Peonies
A P Saunders
   "Most strains of hybrid peonies are sterile during the earlier years of their growth, and this strain follows the usual rule. However, after the plants have attained to full maturity they begin to set an occasional seed. I cannot tell how these seeds have been fertilized. It could be by pollen of the bloom itself; or it could be by wind-borne pollen either from another plant of the same parentage of from anything else in the garden that was in bloom at the time. However that may be, these hybrids do acquire in time the habit of setting a few seeds, though never very many; and these seeds being viable we get from them plants which are the second generation from the original cross.
    In these second generation plants there is a surprising change, for they have regained complete fertility. They have very strong pollen and are regular and fairly abundant seed-setters. Furthermore the plants are taller than the first generation plants and altogether more finished and with much more style."

Distant Hybridization of Crop Plants (1992) G. Kalloo, J. B. Chowdhury, Eds.
Overcoming the barriers in hybridization
G. S. Khush and D. S. Brar
Orton (1980a) reported that the plants regenerated from the tissue culture of a sterile Hordeum vulgare x H. jubatum hybrid had enhanced bivalent formation as compared to the original hybrid, which was asynaptic. Two of the five haploids examined showed a few H. jubatum isozyme bands, indicating that some intergenomic exchanges occurred prior to chromosome elimination (Orton 1980b).

Theor Appl Genet 57(2): 89-95 (Mar 1980)
Cytogenetic analysis of plants regenerated from colchicine-treated callus cultures of an interspecific Hordeum hybrid
T. J. Orton
Department of Crop and Soil Sciences Michigan, State University, East Laming, Michigan
Department of Vegetable Crops, University of California, 95616, Davis, CA
R. P. Steidl
Department of Crop and Soil Sciences Michigan, State University, East Laming, Michigan
Cargill Seeds, 61856, Monticello, IL
Hybrids of Hordeum vulgare (HV) x H. jubatum (HJ) were synthesized for purposes of introgressive breeding, but were sterile and the recovery of pure diploid tillers by colchicine applications in vivo was difficult. Plant regeneration from colchicine-treated callus cultures of the hybrid (HV x HJ) was investigated as a means to produce high numbers of pure diploid, fertile intermediates. 10 of 50 plants regenerated in this manner exhibited variable chromosome numbers with means of approximately 37 (expected diploid number = 42). Cytological examinations of microsporogenesis in all such plants revealed a high incidence of bivalent formation at metaphase I (as compared to nearly complete asynapsis in the F1), but spindle and chromosome abnormalities in later meiotic stages led to complete sterility. Approximately 40% of HJ plants regenerated from colchicine-treated calli appeared to be pure tetraploids of high fertility. These techniques are hence useful for high frequency production of diploid or polyploid plants.

Theor Appl Genet 56(3): 101-112 (May 1980a)
Chromosomal variability in tissue cultures and regenerated plants of Hordeum
T. J. Orton
Department of Botany and Plant Pathology, Michigan State University, East Lansing, Michigan
Spontaneous polyploidy, aneuploidy, and chromosomal rearrangements were observed in callus and suspension cultures of Hordeum vulgare, H. jubatum, and their interspecific hybrid. The extent to which each class of chromosomal variability was present in a culture depended upon differentiated state, age, and history. Cytological and isozymic analysis of subdivided callus cultures revealed spatial segregation of chromosomal variability. Cytogenetic analyses were performed to determine the expression of this in vitro chromosomal variability in corresponding regenerated plant tissues. A complete loss of polyploidy and a decrease in aneuploidy and chromosomal rearrangements were observed. Analyses of specific isozyme activities in regenerates suggested that a quantitative segregation of H. vulgare and H. jubatum genomes had occurred in tissue cultures of their interspecific hybrid. Possible uses of in vitro chromosomal variability for plant breeding and genetical studies are discussed.

The Journal of Heredity 71: 280-282 (1980b)
Haploid barley regenerated from callus cultures of Hordeum vulgare X H. jubatum

Microhybridity, as indicated by the presence of specific HJ isozymes in HVL haploid regenerates could be a consequence of interspecific chromosome transfer by somatic exchange or translocation (chromosomal rearrangements are frequent in these cultures6); or chromosome addition (in eight and nine chromosome cells) or substitution (in seven chromosome cells). Perennial-like growth habit aside, HV-like morphology suggests that whole chromosome substitution is unlikely and asynapsis in eight and nine chromosome metaphase I microsporocytes indicates that extra chromosomes are of HJ origin. Further analyses of phenotypes and cytogenetic studies of doubled HVL X HV hybrids are in progress to elucidate the basis of microhybridity.

Herbertia, 1: 50-62 (1934) (reprint from Gardeners' Chronicle — London, 1901)
Hybridization in Amarylleae
Arthington Worsley
[Hippeastrum] griffini, of the Botanical Magazine, 3528, is cited as a hybrid between H. psittacinum and Johnsoni. Certainly the figure is not typical of H. psittacinum, and the plant is not improbably a hybrid. Yet it cannot be said that its parentage is undoubted, because it appears (in the letter-press) that it was raised by 'W. Griffin in his hothouse at S. Lambeth previous to 1820,' and did not flower till after sixteen years or more had elapsed. Seedlings usually flower in from eighteen months to four years from date of sowing, and in sixteen years or more there was certainly time for many things to happen. (See next item for a similar delay)

Planta 52: 77-95 (1958)
Observations on a Subfertile Fragaria Clone
[Miss Elizabeth] Schiemann's latest paper (1958) dealt with a subfertile hybrid which had originated in 1923 from F. x ananassa x virginiana. Besides having characteristic teratological malformation of the leaves, the plants, propagated vegetatively, came to flower for the first time after sixteen years. From that year on, the malformation of the inflorescences and flowers decreased.

Jour Roy Hort Soc. 23: 90-126 (1900)
Experiments in Hybridisation and Cross-Breeding
C. C. Hurst
It is quite possible that domestication or cultivation may in time eradicate this decline in the fertility of hybrids, for I observe that in my hybrid Berberis x stenophylla, the first hybrids between the two wild species flower more profusely, but bear fewer berries than the parent species; while the hybrids of the second generation are much more profuse in their berry-bearing, being apparently more fruitful even than the wild species. It very often happens that the pollen of very young hybrids is not so effective as that of those of more mature growth. Mr. Reginald Young believes this to be so with his Paphiopedilums; and Dr. Focke records a case of a hybrid Sinningia in which the pollen of the second year of flowering was better than that of the first.

Adaptation in Plant Breeding, 1995: 84
Adaptive properties of Picea abies progenies are influenced by environmental signals during sexual reproduction
Oystein Johnsen & Tore Skroppa
Virtually no information is available about rapid genomic changes or epigenetic effects in spruce. Genomic imprinting is, however, being increasingly accepted as a fundamental and widespread process that determines, in ways not predicted by the laws of Mendelian inheritance, whether a particular gene will be expressed or not (Matzke & Matzke, 1993). Interestingly, Meyer et al. (1992) found that environmental factors influenced 35S promoter methylation of a maize A1-gene construct in transgenic petunia and its colored phenotype. While blossoms on field-grown plants flowering early in the season were predominantly red, later flowers on the same plants showed weaker coloration. The reduction of the A1-specific phenotype correlated with methylation of the 35S promoter. Moreover, they found that the stability of pigmentation correlated with the time of seed production. The A1-gene construct was insensitive to methylation in progeny from flowers of young parental plants produced early in the season, but became susceptible to methylation within progeny from subsequent later crosses. Similar observations have been made in non-transgenic Zea mays where methylation was more pronounced in upper ears and tassels (Federoff & Banks, 1988). So far, we can only speculate that such gene regulation, caused by activation or deactivation of certain genes by environmental conditions during reproduction, regulate the phenotypic expression of adaptive traits in Norway spruce.

J H Nicolas: Memoirs, Horticultural Society of New York, vol 3 (1927)
"Have the soil and original method of propagation a direct relation to the fertility or sterility of a plant? We have long noted here that grafted plants of R. Hugonis, for example, will profusely bear seeds, while plants grown from cuttings are very scant seed bearers, almost approaching sterility. Paul's Scarlet Climber as an own root plant may be considered as sterile, but a grafted plant will bear both self- and hand-pollinated seeds. I have also noted that plants of the same variety in different parts of the nursery have a different seed bearing capacity, although both receive the same amount of sunshine. As an instance, R. bracteata and R. Altaica at one location are practically sterile, while a short distance away, but in a different soil, nearly every bloom, either hand- or self-pollinated, sets fruit."

Van Fleet: American Rose Annual 13: 29-34 (1919)
Owing to its poor seeding abilities when grown as grafted plants on heavy soil, less progress has been made than was hoped for with R. Moyesii [probably R. fargesii], notable among wild roses for the deep red coloring and waxy texture of its widely expanded blooms. Now that our plants have been transferred to the sandy loam of Bell Experiment Plot, and have become established on their own roots, seeds are more freely borne, and a fair number of hybrids are under way. Pollen was plentifully produced, even when the fruits failed to mature, and a few early crosses, the result of applying it to the stigmas of other species and varieties, have sufficiently developed to show prospective value.

F. K. Teterev: in The Situation in Biological Science (1948)
"In 1934-35, we obtained a hybrid by crossing the Vladimirskaya cherry with the Stepnoy almond. Quite by chance, as happens with the formal geneticists, the hybrid turned out to have 24 chromosomes, although a number of the seedlings were found to have another chromosome number. The haploid number of the almond is 9, that of the Vladimirskaya cherry is 16, yet the hybrid had 24 chromosomes. It blossomed profusely, but bore no fruit. But when this hybrid was grafted on to a sour cherry, it blossomed and began to bear fruit. More, when this hybrid was grafted on to a sweet cherry, it even began to bear quite abundant fruit."

W. Herbert: Hybrids and Constitution in Amaryllidaceae (1837)
The fact being established with respect to one genus [Crinum], that the species which have most botanical affinity and general likeness, if they delight in a different state of soil or of atmosphere, produce a barren cross, while the most dissimilar, if they possess the same constitutional predilections, give birth to a fertile plant, cannot remain as an isolated circumstance, but must be considered by every unprejudiced and philosophical mind with reference to the whole vegetable creation.