Unlike some other families (e.g. Cactaceae, Orchidaceae) of flowering plants intergeneric hybrids are relatively scarce in Malvaceae. One might expect more reports of intergeneric hybrids in economically important genera, such as Gossypium (cotton), Theobroma (cacao) and Abelmoschus (okra), but even here, unlike Triticum/Hordeum/Secale (wheat, barley and rye), Saccharum and Brassica/Raphanus (cabbages etc. and radish), reports of intergeneric hybrids are scant.
Intergeneric hybrids in horticulture
Intergeneric hybrids between Chiranthodendron and Fremontodendron (×Chiranthomontodendron lenzii) and between Alcea and Althaea [1] (×Alcalthaea suffrutescens) are in horticultural commerce.
×Chiranthomontodendron lenzii was raised in California [2], and is grown in a small way as an ornamental tree. It previously went under the names ×Leelenzia ranchorum and ×Chiranthofremontia lenzii (neither name is valid under the provisions of the ICNafp), the valid name ×Chiranthomontodendron lenzii being published subsequently.
Hybrids between Alcea rosea and Althaea officinalis were raised in Soviet-era Hungary, and subsequently entered commerce in the west via East Germany.
Experimental hybrids
A hybrid Anoda thurberi × Periptera punicea is reported. [3]
Blanchard successfully crossed Hibiscus indicus and Cenocentrum tonkinense. However these have found to be sister taxa in DNA studies of Hibisceae, and may well end up as congeneric in a future revision of the taxonomy of Hibisceae.
A 1980 paper reports a hybrid between Gossypium hirsutum and Hibiscus panduriformis [4]. This paper cites earlier Russian [a] and Chinese [b, c] work reporting hybridisation between Gossypium and several species in Hibisceae and Malveae.
Ambiguously intergeneric hybrids
Herrania differs from Theobroma sensu strictu in a number of characters, and from the mid-20th Century was considered an accepted genus [, ], but DNA studies have found to be nested with Theobroma and following recent paper [] it is now commonly considered part of Theobroma sensu lato. A program of experimental hybridisation among Theobroma and Herrania species [5] included attempts at obtaining hybrids between Theobroma cacao and Herrania mariae; fruit and seed set was achieved, but no germination. Possibly techniques such as ovule or embryo culture could overcome this barrier.
Gossypium was earlier divided into several genera. Known experimental hybrids in this genus include hybrids between several of the previously recognised genera, including ×Hemiultragossyium harknutum.
Hybrids are known between Malva and Lavatera in their traditional circumscriptions. When Lavatera is sunk in Malva these become intrageneric hybrids under more modern conceptions of the genera. Among the wider crosses a hybrid between Lavatera trimestris and Malva 'Bicolor' is reported [6], and Malva alcea has been identified as a palaeohybrid of Malva moschata and Lavatera thuringiaca.
The name ×Malvalthaea transcaucasica is applied to putative (palaeo?)hybrids between Malva aegyptia and Althaea hirsuta, but this is another instance where both parents are now placed in Malva.
The genus Hibiscus as commonly conceived is massively paraphyletic. If proposals to divide the genus (thereby treating Hibisceae consistently with Malveae and Gossypieae) are adopted some intrageneric hybrids within Hibiscus (e.g. Hibiscus mutabilis × Hibiscus moscheutos) might become intergeneric.
Soviet and Chinese work
A paper from the Soviet Union [a] and two related book chapters [7, d] report hybrids between Gossypium on the one hand, and several other genera of Malvaceae; including Abelmoschus, Alcea, Hibiscus and Malva. Two papers from China [b, c] report the production of hybrids between Gossypium hirsutum and/or arboreum with Hibiscus rosa-sinensis.
Gossypium hirsutum × Hibiscus panduriformis
It is reported that a single viable seed of this hybrid was obtained from 2,000 pollinations of a male-sterile Gossypium hirsutum, representing a hybrid production rate of less than 0.01%, even in the absence of competition from cotton pollen.
The hybrid is generally intermediate between its parents. It is an annual, which shares with cotton the presence of gossypol glands, foliar and involucral nectaries, and a fruit in the form of a boll, and with the other parent the presence of hairs on all vegetative parts. The leaves are cordate (like both parents), and 3-5 lobed, but not as deeply as in cotton. The bracteoles number 3. They are laciniate, as in cotton, but not cordate. The calyx is campanulate. The corolla favours Hibiscus panduriformis in its yellow colour with a darker central spot. The anthers are arranged as in Hibiscus panduriformis.
Meiosis in the pollen of the hybrid was investigated. It has 38 chromosomes (intermediate between the 52 and 24 chromosomes of the parents). During metaphase there are up to 19 bivalents, but most commonly 12 or 13 (which is still higher than is common in haploid Gossypium hirsutum - possibly Hibiscus panduriformis is also a palaeotetraploid). Segregation of chromosomes during anaphase was assymetric, with the common division being into groups of 12 and 26 chromosomes, which suggests to me reconstitution of the parental genomes. Pollen fertility is about 60%. The hybrid is fertile, but seed set is lower than in the parents.
Vysotskii published multiple papers [a, e, f] and book chapters [7, d] reporting wide hybridisation with Gossypium as the seed parent. This work is little cited and mostly inaccessible, but a translation of one of the book chapters mentions the use of Abelmoschus esculentus (as Hibiscus esculentus), Alcea nudiflora, Alcea rosea, Hibiscus cannabinus, Hibiscus coccineus, Hibiscus moscheutos, Malva neglecta and Malva verticillata (as Malva pulchella). A earlier chapter [d] adds Hibiscus rosa-sinensis to the mix. Nothing is said about the results of crossing with Hibiscus moscheutos and Malva pulchella. I don't know how to interpret these works; taking the papers at face value possible hypotheses include androgenesis, stimulative parthenocarpy, and self-fertilisation of the seed parent, as well as genuine hybridisation. The reported results are as follows :-
Similar work has subsequently been performed in Greece, with Abelmoschus esculentus, Hibiscus cannabinus and Malva sylvestris as the seed parents. [8] This cites neither the Soviet (Vyotskii) nor the Chinese (Chow) work.
Teshima reported obtaining seed of the cross Abelmoschus esculentus × Gossypium hirsutum, but this failed to germinate. [9] This could have been inviable hybrid seed, or inviable haploid seed resulting from stimulative parthenocarpy. Subsequent work has obtained plants which are aneuploid Gossypium from the application of Abelmoschus esculentus pollen to Gossypium. [g, h]Mavromatis et al obtained similar results, but using embryo-ovule culture raised plants which were found to be Gossypium aneuploids. (Compare with the production of haploid wheat plants by fertilisation with maize pollen.)
Surprisingly none of the reports of intergeneric hybrids with Gossypium seem to have been followed up. However, the report of a hybrid with Hibiscus panduriformis seems to be robust, which suggests that wide hybrids can be obtained in Malvaceae, if sufficient attempts are made. On the other hand attempts to create hybrids by somatic cell fusion of Hibiscus rosa-sinensis and Lavatera thuringiaca have been unsuccessful, and the application of Abelmoschus esculentus pollen to Gossypium results in the development of chromosomally abnormal cotton plants [g].
References
Bibliography
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© 2008, 2011, 2020, 2025 Stewart Robert Hinsley