Rare plant of the month: June 2017

Lathyrus belinensis

belinensis (2) COMPRESSED

Lathyrus belinensis Copyright: R Parsons

In this instalment of our series, which looks at reasons why we need to be aware of the importance of conserving the rare plants that grow in our gardens in the UK and Ireland, we explore Lathyrus belinensis, a plant with a significant history of discovery, loss and an important place in plant breeding.

Lathyrus belinensis is a yellow and orange-flowered species which may hold the key to the holy grail of the plant breeding world – a truly yellow sweet pea. You may recognise it from the cover of the 2016 Plant Heritage Directory.

The discovery of the plant, in a graveyard close to the village of Belin, led to it being recognised as a new species and subsequently named Lathyrus belinensis (Maxted & Goyder 1988).

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Original site of L. belinensis growing on hillside. Copyright N Maxted

Closely related to L. odoratus (sweet pea), L. belinensis was found in 1987, in the Turkish province of Antalya, by Ayse Kitiki (Aegean Agricultural Research Institute), Bob Allkin (RBG, Kew) and Nigel Maxted (University of Birmingham) during a research trip, involving locating significant crop wild relative (CWR) species. Dr Maxted was then based at the University of Southampton which housed the Vicieae database project and seedbank.

The single population was found growing alongside a new road, but upon returning to the site in 2010, Nigel found that the original location had been completely destroyed  and although some plants were still found in the area, the richest area within the site had been lost.

Nigel Maxted wrote:

Police station and excavated hillside

Police station and excavated hillside. Copyright N Maxted

The type population was found over an area of only 2 km2 and although the species was published in 1988, no further populations have been reported. The only known population is found adjacent to a new main road that carries holiday traffic along the coast in an area ripe for tourism development and is in an area that was being planted with conifers at the time of original collection. On returning to the site in 2010 it was found that the original type location had been completely destroyed by earthworks associated with the building of a new police station. Although some plants were still found in the area and seed is held ex situ, the richest area within the site had been lost. In part to draw attention to the need for active in situ conservation of L belinensis it has been recently assessed using the IUCN Red List Criteria and found to be Critically Endangered – the most highly threatened category. The species has real economic potential as a CWR donor yet it is near extinction in the wild. (Maxted 2012)

Small remaining population COMPRESSED

Remaining population of 30 plants. Copyright N Maxted

Nigel returned to Belin in May this year (2017) to find a small group of only 30 plants still in situ, near the police station and widened road.

Crop wild relatives are the wild ‘cousins’ of our cultivated plants and crops. They are important because they contain useful genetic diversity, some of which is not present in cultivated crops and therefore may have significant resistance to disease and other pathogens. According to Poulter et al (2003), an unexpected benefit from L. belinensis, is that hybrid material has been found to resist Powdery Mildew a problem disease for Sweet Pea growers in hot, dry conditions.

In 1993, Roger Parsons, National Collection Holder of Lathyrus, received seed collected in Belin from the University of Southampton seedbank and passed the species to former National Collection Holder, the late Sylvia Norton. Although the seed is listed in several seed catalogues, it no longer appears in the RHS Plant Finder, the true species having been last listed in 1998.

‘Goldmine’ is a cultivar name used in the trade for L. belinensis. However it is currently wrongly listed as L. odoratus ‘Goldmine’ in some catalogues, demonstrating how unregulated commercial naming of plants, that are not food crops, can create confusion in the industry.

Roger Parsons writes:

What makes this species so special is that it is very closely related to the Sweet Pea, L. odoratus, and has genes for yellow flower pigment. Producing a yellow Sweet Pea has long been one of the holy grails for plant breeders. Lathyrus species very rarely hybridise and the few successes have involved techniques such as stylar amputation and embryo rescue. A team in New Zealand were able to successfully cross the old-fashioned Sweet Pea ‘Mrs Collier’ with the Belin Pea (Hammett et al 1994) and the F1 hybrid has been described as L. x hammettii. Although self-sterile, this hybrid produced pollen which was back-crossed and later crossed with other Sweet Peas. Over a period of time, a succession of crosses using hybrid material has resulted in new cultivars of Sweet Pea with interesting or novel characters (Edwards 2014). The elusive yellow is still awaited but a pure yellow cultivar with L. belinensis form is one step in that direction.

Deviation from L. belinensis_7877 COMPRESSED

Deviation from L. belinensis. Copyright R Parsons

L. belinensis has real economic potential as a parent plant and having been assessed as critically endangered using IUCN Red List Criteria, it is expressly important that it’s being safely held in National Plant Collections, such as Roger Parson’s. National Plant Collections are valuable resources for protecting species and cultivars that hold genetically diverse material for plant breeding. Plants which are valuable for economic or ‘utilitarian’ reasons, for example, those with the ability to produce offspring with ground-breaking characteristics, or that can significantly combat disease and climate change, or which contain useful chemicals or are super attractive to a particular insect.

References:

N. Maxted & D.J. Goyder 1988 A new species of Lathyrus sect. Lathyrus from Turkey. Kew Bulletin 43(4): 711-713

R. Poulter, L. Harvey & D.J. Burritt 2003 Qualitative resistance to powdery mildew in hybrid sweet peas. Euphytica 133: 349-358

N. Maxted 2012 Lathyrus belinensis: a CWR discovered and almost lost. Crop Wild Relative 8: 44

K.R.W. Hammett, B.G. Murray, K.R. Markham & I.C. Hallett 1994 Interspecific hybrization between Lathyrus odoratus and L. belinensis. Int.J.Plant Sci. 155(6): 763-771

D. Edwards 2014 Developing a yellow Sweet Pea. New Plantsman 13(4):252-4

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