Re: [Aroid-l] Intrageneric crossing - a good reference



From : 	Peter Matthews <pjm@gol.com>



Reply-To : Discussion of aroids <aroid-l@gizmoworks.com>

Sent : Monday, January 23, 2006 1:13 AM

To : Discussion of aroids <aroid-l@gizmoworks.com>

Subject : Re: [Aroid-l] Intrageneric crossing - a good reference





Dear Peter,



Thanks---to put this in a nutshell, it is suspected and confirmed by the
1988 testing that the ORIGINAL collected plant was a hybrid between two
COLOCASIA species, C. esculenta X C. gigantia, not between a Colocasia X
Alocasia. AND--a cross between Alocasia brsibanensis X Colocasia
esculenta was made by man, ONE seed developed into ONE plant. This
confirms that a cross is remotely possible between these two seemingly
closely related genera, in which the dividing lines between these two genera
are still vague, and that it is easier for two different species within the
SAME genus can and will cross.



Julius






reference




H. Yoshino, T. Ochiai and M. Tahara (2000) Phylogenetic relationship between
Colocasia and Alocasia based on molecular techniques. In: D. Zhu, P. B.
Ezyaguirre, M. Zhou, L. Sears and G. Liu (eds) Ethnobotany and genetic
diversity of Asian taro: focus on China. International Plant Genetic
Resources Institute and Chinese Society for Horticultural Science, Beijing.
pp. 66-73.



Summary:



A taro strain collected in Nepal in 1973 was considered to be an
intergeneric hybrid between Alocasia and Colocasia, on the basis of
chloroplast DNA analyses carried out in the 1980s (but see later work with
isozymes, noted below).



Subsequently, an artificial cross was attempted and numerous seeds were
obtained after a cross between C. esculenta var. aquatilis (Hassk.) Kitamura
(from Nepal) and Alocasia brisbanensis (F. M. Bailey) Domin (ex Kyoto
Botanical Garden). Most seeds did not germinate and only a single plant
developed fully.



This plant was triploid and chromosome painting using genomic in situ
hybridisation (GISH) showed that 14 of 42 chromosomes were derived from A.
brisbanensis.



It was concluded that the plant was an intergeneric hybrid, formed as an
unreduced egg of C. esculenta fertilised with normal A. brisbanensis pollen.



Isozyme analyses by V. X. Nguyen (1998), PhD, Okayama University,
contradicted the original interpretation of the Nepalese hybrid, indicating
that it was a cross between C. esculenta and C. gigantea (i.e.
intra-generic, not inter-generic).



*****

Comments by PJM:



Among other Asian accessions (Nepal and China) Nguyen found further examples
of hybridsation between C. esculenta and C. gigantea. Taxonomically, C.
gigantea is possibly misplaced in Colocasia, but it is not necessarily to be
regarded as closer to Alocasia. As Yoshino points out, and as Tony Avent
indicates in this list, there is much to be learned about hyribidisation
among these aroids.



The experimental survival of a hybrid between genera was made possible by a
rare polyploidisation event that allowed odd chromosomes to be carried along
by a normal full complement of chromosomes.



Vigorous offspring are less likely after intergeneric crosses than after
interspecies (intrageneric) crosses. An intergeneric crossing has not yet
been proven to occur in the wild, though it is possible in principle.



PJM



*****







Dear Pete and Marek:



The Alocasia x Colocasia hybrid that you mentioned looks a lot like A.
macrorhizos. I was fortunate to examine this hybrid several years ago
growing at a Hawaii taro research station. It was found in an area of Nepal
where the two genera grow together. On our expedition last year to N.
Vietnam, we visited a restricted military area near the China border. We
found Colocasia gigantea growing with Alocasia macrorhizos. Growing among
them were several plants that superficially appeared to be bi-generic
hybrids. We have not had these plants tested yet to confirm this yet, so
this is just a preliminary observation. If anyone is doing work in that
region, I will be glad to direct them to the population for further study.



Tony Avent

Plant Delights Nursery @

Juniper Level Botanic Garden

9241 Sauls Road

Raleigh, North Carolina 27603 USA

Minimum Winter Temps 0-5 F

Maximum Summer Temps 95-105F

USDA Hardiness Zone 7b

email tony@plantdelights.com

website http://www.plantdelights.com

phone 919 772-4794

fax 919 772-4752

"I consider every plant hardy until I have killed it myself...at least
three times" - Avent









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Peter Matthews (Dr)

National Museum of Ethnology

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Osaka 565-8511, Japan

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****



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Plant genetic resources in Eurasia



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