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Hybridity of lepidotes in Rhododendron subsection Ledum
based on some hybridization results

Kristian Theqvist, 7-Mar-2013, rev. 013

 

Note: The ploidy levels have not been updated to the latest results from flow cytometry tests! The table needs to be updated!


Note: The hybridity is based only on a small sample basis and several factors could affect on whether the pollination is successful. In some cases there was very scarce of pollen and that could be a reason for not getting seeds.
Criteria for "Hybridity evident": Seeds have germinated and at least some of the seed plants show features that differ from the wild R. tomentosum.

Cross with another Rhododendron species

Seed parent: R. tomentosum (Ledum tomentosum, Ledum palustre), chromosome number 2n = 52, tetraploid

Subsection
(or section) in alphabetic order

Pollen parent / Species

2n

Year

Hybridity evident

Comment on seed plants

Boothia

leucaspis

?

2004

Yes

Germination 80 % resulting in 24 seed plants.

Caroliniana

minus (Milde)

26

2003

Yes

Germination 72 %. 20 seed plants. Very large variation, mostly vigorous, some weak ones.

minus, pink (Göteborg)

26

2003

No

No seeds.
minus (Bergianska)

26

2005

?

36 seeds but germination 0% and no plants.

Caroliniana
(or x Rhododendron ?)

minus (Hachmann)  Looks like a cross minus x ferrugineum?

?

2003

Yes

Germination 100 %. 21 seed plants. Very large variation, vigorous except one weak.

Cinnabarina

cinnabarinum var. cinnabarinum

104

2003

Yes

Germination 100 %. 41 seed plants. Very large variation, mostly vigorous, some quite small.

cinnabarinum var. xanthocodon

104

2005

Yes

Germination 40 %. 12 seed plants.

Edgeworthia edgeworthii
26?
2006
tbd
35 seeds, germination successful.

Heliolepida

desquamatum (rubinosum)

52

2005

Yes

Germination 23 %. 7 seed plants.

Lapponica

fastigiatum SBEC 0804

52

2005

Yes

Germination 63 %. 19 seed plants.

fastigiatum C&H 7022

52
2006
tbd
41 seeds, germination successful.

hippophaeoides

26

2003

Yes

Germination 77 %. 25 seed plants. Very large variation, mostly vigorous, only few weak ones, some with chlorophyll defects that later on dissappered.

hippophaeoides Album

26 (?)

2005

?

18 seeds but germination 0% and no plants.

impeditum

26

2003

?

Too few weak seeds to make decisive conclusion on hybridity.  No plants.

impeditum

26

2004

Yes

Germination 43 %. 13 seed plants.

lapponicum var. parvifolium

26

2004

Barely

Not many seeds. Germination 44 %. 4 seed plants.

lapponicum, New Foundland

26

2004

?

Not enough pollen? No seed.

lapponicum, New Foundland

26

2005

Yes

Germination 60 %. 18 seed plants.

polycladum

52

2006
tbd
77 seeds, germination successful.

russatum

52

2004

Barely

Not many seeds. Germination 30 %. 3 seed plants.

russatum var. cantabile

52

2004

Yes?

A lot of seeds, but germination only 3 %. Only 1 weak seed plant.

tapetiforme

78 (?)

2004

Yes

Germination 20 %. 6 seed plants.

tsaii

?

2006
tbd
500 seeds, germination successful.

yungningense

52

2004

Barely

Not many seeds. Germination 11 %. Only 1 seed plant.

yungningense

52

2006
tbd
400 seeds, germination successful.

Ledum

diversipilosum
(Ledum palustre var. diversipilosum )

52

2005

Yes

Germination 80 %. 24 seed plants.

groenlandicum
(Ledum groenlandicum )

52

2003

Yes

Germination 90 %. 35 seed plants. The seed plants looked more groenlandicum than tomentosum, some variation in leaf color and shape, some malformed ones.
Extremely vigorous growth.

hypoleucum
(Ledum  hypoleucum)

52

2003

Yes

Germination 55 %. 16 seed plants. Very large variation, some vigorous, some quite small.

subarcticum
(Ledum  palustre ssp. decumbens)

26

2004

?

Not enough pollen? Only 3 small seeds, no germination, no seed plants.

subarcticum
(Ledum  palustre ssp. decumbens)

26

2005

Yes

Germination 37 %. 11 seed plants.

'Milky Way' (selected form)

52

2004

Yes

Germination 90 %. 27 seed plants.

Maddenia veitchianum

26?

2004

Yes

Germination 60 %. 18 seed plants.

lindleyi
(picture © Glendoick Gardens)

26

2005

Yes

Germination 60 %. 18 seed plants.
burmanicum
?
2006
tbd
57 seeds, germination successful.
Moupinensia dendrocharis

26 (?)

2005

?

Only 2 small seeds, no germination, no seed plants.
dendrocharis

26 (?)

2006
tbd
65 seeds, germination successful.
Pogonanthum sargentianum

26

2004

?

Only 6 small seeds, no germination, no seed plants.
Rhododendron ferrugineum

26

2005

?

13 small seeds, no germination, no seed plants.
ferrugineum

26

2006
tbd
115 seeds, germination successful.
ferrugineum Album

26 (?)

2005

Barely

70 seeds, mostly small, germination 10 %, 3 seed plants.
hirsutum

26

2005

Barely

22 seeds, germination 9 %, 2 seed plants.
x intermedium

26 (?)

2005

?

3 small seeds and lost.

Rhodorastra

dauricum

26

2003

Yes

Germination 22 %. 8 seed plants. Large variation, some with leaves without hairs.

ledebourii (variety of dauricum)

26

2003

Yes

Germination 30 %. 14 seed plants. Large variation, some with leaves without hairs.

mucronulatum var. chejuense

26

2006
tbd
43 seeds, germination successful.
Saluenensia calostrotum ssp. keleticum  

26

2004

?

Only 6 small seeds, no germination, no seed plants.
calostrotum ssp. keleticum  

26

2005

No

No seeds.
prostratum

52 (?)

2005

No

No seeds.
saluenense  

26

2004

Yes

Germination 63 %. 19 seed plants.
Scabrifolia

spinuliferum (picture at www.rhododendron.dk, taken by Hank Helm)   

26

2004

No

 No seeds.

spinuliferum (picture at www.rhododendron.dk, taken by Hank Helm)   

26

2005

No

 4 small seeds, no germination, no seed plants.
spinuliferum (June Sinclair)

26

2004

Barely

Not many seeds. Germination 75 %. 6 seed plants.
Tephropepla hanceanum 'Canton Consul'

?

2005

Yes

Germination 66 %. 19 seed plants.
Triflora, Augustinii / Triflorum Alliance ambiguum

52

2004

Yes

Germination 40 %. 12 seed plants.
augustinii

52

2004

Barely

Not many seeds. Germination 13 %. Only 1 seed plant.
augustinii

52

2005

No

No seeds.

chengshenianum (ambiguum)

52 (?)

2005

?

6 small seeds, no germination, no seed plants.
concinnum

52

2004

Barely

Not many seeds. Germination 20 %. 2 seed plants.
concinnum var. pseudoyanthinum

52

2004

Barely

Not many seeds. Germination 75 %. 3 seed plants.
keiskei 'Yaku Fairy'

26 (?)

2004

Barely

Not many seeds. Germination 36 %. 4 seed plants.
Triflora, Yunnanense Alliance

hormophorum (yunnanense)

78 (?)

2005

?

3 small seeds, no germination, no seed plants.
yunnanense

78

2004

Yes

Germination 43 %. 13 seed plants.
Triflora, Oreotrephes Alliance oreotrephes

78

2004

No

No seeds.
oreotrephes

78

2005

?

Swelling seed pods disapperared
Section Tsutsusi kiusianum

26

2003

No

 No seeds.

Cross with a Rhododendron hybrid

Seed parent: R. tomentosum (Ledum tomentosum, Ledum palustre), chromosome number 2n = 52, tetraploid

Pollen parent / Hybrid
in alphabetic order

Subsection
(or section)

2n

Year

Hybridity evident

Comment on seed plants

'Aquamarin', (augustinii hybrid)

Triflora x

?

2004

No

 No seeds.

'Biskra'
(cinnabarinum Roylei Group x ambiguum)

Cinnabarina x Triflora

?

2004

Yes

Germination 55 %. 12 seed plants.

'Biskra' x cinnabarinum var. xanthocodon

(Cinnabarina x Triflora) x Triflora

?

2004

Barely

Not many seeds. Germination 7 %. Only 1 seed plant.

'Blumiria'
(impeditum x ?)

Lapponica x ?

?

2003

Barely

Not many seeds. Germination 60 %. 5 seed plants. Large variation on few plants, a couple of vigorous ones.

'Charme La' minus Carolinianum Group x pemakoense Patulum Group

Caroliniana x Uniflora

?

2006
tbd
200 seeds, germination successful.

'Countess of Haddington'
(ciliatum x dalhousiae)

Maddenia x

?

2005

?

3 small seeds, no germination, no seed plants.

'Curlew' ( ludlowii x fletcherianum)
(picture © Glendoick Gardens)

Uniflora x Maddenia

?

2005

?

7 small seeds, no germination, no seed plants.

'Dörte Reich'
(minus x cinnabarinum Concatenans) (picture © Glendoick Gardens

Caroliniana x Cinnabarina

?

2003

Yes

Germination 67 %. 9 seed plants. Some variation, all very vigorous.

'Flämingperle' (hippophaeoides hybrid)

Lapponica x ?

52

2005

Yes

Germination 53 %. 16 seed plants.

'Isola Bella'
(dauricum 'Artic Pearl' selfed) x fletcherianum 'Yellow Bunting'

(Rhodorastra x) x (Maddenia x)

?

2004

Barely

Not many seeds. Germination 30 %. 3 seed plants.

'Johnsonianum'

Unknown

?

2005

No

No seeds.

'Mother Greer'
(hippophaeoides x ?)

Lapponica x ?

?

2003

No

 No seeds.

'P.J.M. Elite'
(minus x dauricum)

Caroliniana x Rhodorastra

?

2003

Barely

Germination only 25 %. 6 seed plants. Large variation, mostly vigorous.

'Princess Anne'
(picture © Glendoick Gardens)
(hanceanum x keiskei)

Tephropepla x Triflora

?

2004

Barely

Not many seeds. Germination 60 %. 6 seed plants.

'Puncta' (ferrugineum x minus var. minus, parentage uncertain)

Rhododendron x Caroliniana ?

?

2005

Barely

Only 11 seeds, germination 18 %, 2 seed plants.

'Ramapo'
(fastigiatum x minus)

Lapponica x Caroliniana

?

2003

Barely

Not many seeds. Germination 38 %. 3 seed plants. Large variation on few plants, a couple of vigorous ones.

'Robert Seleger'
(calostrotum ssp. keleticum x ?)

Saluenensia x ?

?

2003

No

 No seeds.
'Schneeflöckchen' (trichostomum hybrid)

Pogonanthum x

?

2004

?

Only 6 seeds, no germination, no seed plants.
Note: 2n is the chromosome number. The chromosome numbers are mainly from the Rhododendron Year Book 1950.

Lepidote Crosses in 2003 using Rhododendron tomentosum as Seed Plant
Pollinations in 2004 using Rhododendron tomentosum as Seed Plant
Pollinations in 2005 using Rhododendron tomentosum as Seed Plant
Pollinations in 2006 using Rhododendron tomentosum as Seed Plant
Taxonomy of species in Rhododendron subsection Ledum