Leguminosae : key achievements 2006 - 2011

Across Kew we have seen significant growth in our legume collections since 2005. The whole legume collection of c 750,000 specimens has been moved (2010-2011) to the new Wing E building of the Herbarium (HLAA). The 740 currently recognized legume genera have been rearranged by a new classification based largely on Legumes of the World, a major legume team output published in 2005; this radical update of the previous Bentham and Hooker (1865) arrangement greatly improves the level of predictivity of useful characteristics between related genera.

Published books include: Wood anatomy of the Mimosoideae (2006), a preliminary List of the Leguminosae in northeastern Brazil (2006), two legume volumes in the Flora Zambesiaca series (both published in 2007), a synopsis of American species of Acacia (2007), and more recently a monograph of the genus Berlinia (2011), and Leguminosae subfamily Mimosoideae for the Flora of the Guianas (2011). The Team`s publications contributed c 6,000 taxon accounts. Twenty-eight legume species pages, published electronically, were contributed by team members.

In the past five years Kew has contributed to a multi-disciplinary, international collaboration on Caesalpinioideae, a programme largely supported by the US National Science Foundation. A number of genus level studies (e.g., a revision of Talbotiella published in 2010) and subfamily level analyses have been undertaken and published in a series of internationally co-authored papers. The project has become part of a larger one coordinated by the recently established international Legume Phylogeny Working Group (LPWG) that has as a central goal the production of a new family classification.

A prototype of a web-based project, Legumes of the World Online (LOWO), has been built. A key feature of the prototype is its ability to browse both phylogenetic data as well as the more traditional tribal scheme used as chapters in the book Legumes of the World. We are now looking for funding to make the prototype deliver content online, thus enabling subsequent editions to be easily produced. Legumes, with over 1,000 Red List assessments, are a key component of the Sampled Red List Index project. Results of this project suggest that 12% of legume species are threatened in the wild.

The biogeography of Leguminosae project was completed in 2010. A major result of the project is the discovery that much of the present diversity in the family is Neogene in age, which is too recent for disjunctions to be explained by continental history, e.g., large-scale continental movements and land-bridges. The historical legacy of these metacommunities is thus one of dispersal assembly within similar ecological settings world-wide. The arid Tethyan Sea track origin of Leguminosae proposed in Legumes of the World, which superseded the prevailing wet equatorial megathermal origin hypothesis of the family, was supported at the species level in a phylogenetic and biogeographical analysis of Indigofera (2009), the third largest genus in the family.

Systematic phytochemistry studies of legumes have continued since 2006 with a number of genera targeted for analysis. For example, in Sophoreae detailed chemical studies of Cladrastis and Styphnolobium have revealed 16 flavonoids new to science with some common to both taxa. Structural features of two previously unreported flavonoids discovered in Cordyla supported a proposed relationship with Milbraediodendron. Advances in modern analytical techniques, such as the combination of high performance liquid chromatography with mass spectrometry (LC-MS), means that only small fragments are needed to perform these surveys and makes the extensive herbarium legume collections accessible to sampling.

Two major reviews on isoflavonoids in Leguminosae were published in 2007 and 2009, the first covering the literature from 1997 to 2004 and the second the literature from 2005 to 2007. All major isoflavonoid subclasses are surveyed; 570 compounds were described with an emphasis on chemosystematic, ecological, and economic significance. A third article in the series is intended for publication in 2012.

A first full account of Polygalaceae pollen was published in 2008. Eight Polygalaceae genera were palynologically studied for the first time. Further legume pollen studies focused on the evolution of polyads in mimosoid legumes, pollen morphology of the Dimorphandra group, and functional significanace of single grain pollen versus polyads in different environments. Plans have been made to expand a study of Cercideae pollen into a multidisciplinary collaborative project combining molecular with morphological data to better understand inter and intra-generic relationships.

Research is currently being conducted on occurrence and role of homoglutathione across legumes to better understand the phylogenetic and chemotaxonomic significance of different homologues. Moreover, research into DNA laddering, volatile production and changes in gene expression during ageing has been conducted using seeds of Pisum sativum, and infrared thermography has been used to diagnose seed quality non-invasively. Seeds of some legumes are intolerant of drying, including Parkia speciosa (a food species from Asia), requiring the development of an innovative conservation strategy. Using differential scanning calorimetry to reveal the physical changes in water during cooling, it has been possible to successfully cryopreserve shoot-tips of this species.

A paper on wood anatomy of Caesalpinia s.l. (which contains c.135 species in 8 genera) was published in 2009, and research is currently being undertaken on species of the much larger and more challenging Australian Acacia (over 1000 taxa).

During the report period, Team members supervised a total of ten PhDs (nine completed between 2006 and 2011) and one MSc. The legume newsletter Bean Bag was compiled, edited and distributed (mainly electronically) annually to c 600 international colleagues specialising in legume research.

The legume team has a robust conservation agenda. Nine legume accounts have been contributed to four Cameroon conservation checklists published in 2010 and 2011, including the Cameroon Red Data Book. A synopsis of Acacia (2007) included 125 global conservation assessments. Conservation assessments are being prepared for 180 species of Indigofera in southern Africa.

Research into the phytochemistry, wood anatomy, biological interactions and sustainable uses of legumes is a major component of the teams work. A team member co-edited the book: The Lentil: An Ancient Crop for Modern times (published in 2007) and also contributed two chapters. Phytochemistry research contributed a number of papers in higher impact journals and broad chemical surveys that contribute to a better understanding of sustainable local use through highlighting compounds of potential benefit and economic value. Examples of recent outcomes include discovery of a chemical marker for Brasilian rosewood (timber of Dalbergia nigra) to assist enforcement of CITES regulations and the authentication of the Chinese herbal medicine ingredient, fructus sophorae (fruits of Styphnolobium japonicum).

As part of an EU-funded project (2009-2012; value to Kew €100,000) the Team conducted farmer surveys about pesticidal plant use in southern Africa and determined that the most widely used species was the legume Tephrosia vogelii. The team, as part of a new consortium, subsequently won additional funding from the McKnight Foundation (2010-2014, US$100K income to Kew) to optimise pesticidal technologies based on Tephrosia vogelii and Neorautanenia mitis for control of insect pests of beans (Phaseolus vulgaris) and cowpea (Vigna unguiculata) grown by resource poor farmers in sub-Saharan Africa.

As part of a project funded by the European Development fund (2006-2009, value to Kew €90,000) the Team validated biological activity of the insect controlling tree species Securidaca longepedunculata (Polygalaceae) in field trials and determined that the biological activity was caused by saponins and methylsalicylate located in root bark. The Team has used this information to investigate new ways of sustainably using the plant material to control stored pests of grain in sub-Saharan Africa.

Legume team members contributed to the identification and synthesis of cicerfuran – a 2-arylbenzofuran from Cicer bijugum. The compound confers resistance to pathogenic fungi of chickpeas and also has biological activity against other bacteria, fungi and Leishmania spp.; this has led to two well-cited research papers.

Two species of Mimosa, and Poincianella pyramidalis are the subject of detailed work on coppicing and pollarding as well as sustainable use of these species for charcoal production in the caatinga vegetation of northeastern Brazil.

Research activities and outputs are especially concentrated in the Breathing Planet Programme strategies 1, 2, 4 and 5.

Conferences and workshops (a selection)

Seven members of the legume team presented papers at the XVIII International Botanical Congress, Melbourne, Australia in July 2011, four at the 5th International Legume Conference in Buenos Aires in 2010 and four at the American Society of Botany, “Botany without Borders” conference in Vancouver, Canada in 2008.

Since 2006, 15 legume seed contributions have been presented at 12 international conferences, along with seven presentations of legume systematic phytochemistry studies. Legume wood anatomy has been presented at two PROTA timber workshops and two IAWA meetings on wood science and anatomy.

The Team also presented at the Young Systematists Forum at the NHM in 2007, at the Linnean Society Palynology Specialist Group meeting (2008); at the XVII (2007) and XVIII (2010) National Botanical Congresses in Mexico, at the International Biogeography Society Meeting in Crete in 2011, and at the International workshop on global legume diversity assessments, Kyushu University, Japan, in August 2011. In collaboration with staff at RBG Edinburgh the team continued to organize annual UK legume workshops.

International Policies

Several legume projects contribute to the GSPC, target 1, 2, and 3.

Data gathered on legume isoflavonoids have been used to inform chemical authentication work on Dalbergia woods relevant to implementation of CITES trade regulations.

Science Team Leader: Gwilym Lewis