Agriculture Reference
In-Depth Information
lupinoid by Corby (1988) because it is commonly found in lupins (Fig. 1.1). Similar
nodule structure is found in all eight species of section Listii (Ardley et al., 2008), but
no other sections of the genus sampled so far (Sprent & van Wyk, unpublished data),
which is interesting in view of the likelihood that section Listii may form the basis
of a separate genus (B.E. van Wyk, personal communication). Clearly this tribe is of
considerable interest for its nodulation characteristics.
Tribe Genisteae is also interesting from a nodulation point of view, but its character-
istics are different from those of the Crotalarieae. Most of the genera are woody shrubs
from Mediterranean regions, extending into Africa and sometimes into mountainous
regions, especially in the New World. The largest genus,
Lupinus
, is complex, but has
been widely studied because of its ability to grow on poor acid soils and because
some of its species, such as
L. albus
, are important grain legumes. There are regular
international symposia for the lupin fraternity, held in very different locations, such as
Iceland, New Zealand and Australia. Genera in Genisteae are nodulated by a variety of
-rhizobia, with none yet known to use bacteria outside this group. Lupin nodules are
formed following a type of epidermal infection and infection threads are rarely seen. In
Cytisus
(under its previous name
Chamaecytisus
), infection threads are transient and are
not part of the infection mechanism (Vega-Hern andez et al., 2001). A detailed study of
Genista tinctoria
also found that the infected tissue contained no uninfected cells (Kalita
et al., 2006). More details of nodule structure and its significance will be given in
Chapters 3 and 5. Species of
Lupinus
are amongst those that can grow at high altitudes
and their isolation in some such locations has enabled them rapidly to develop new
species (Hughes & Eastwood, 2006). Legumes in mountain habitats will be considered
in Chapter 2. Because of their ability to grow on poor soils and exposed locations, many
genistoid legumes, especially species of
Cytisus
and
Ulex
, have invaded areas such as
Australia and New Zealand where they are generally regarded as noxious weeds. The
genus
Polhillia
is native to the CFR and its nodulation status is not known.
Amorpheae
Tribe Amorpheae is placed close to the Dalbergioid clade in Lewis et al. (2005). Its gen-
era are listed in Table 1.10. All are from North or Central America, with some extending
into South America. Most have xerophytic characteristics and can grow in desert areas.
Tab l e 1 . 10
Tribe Amorpheae
Genus
Species
Nod.
Amorpha
L.
15
7
Apoplanesia
C. Presl.
1
?
Dalea
L.
∼
160
17
Errazurizia
Phil.
4
?
Eysenhardtia
Kunth.
∼
10
1
Marina
Liebm.
38
1
Parryella
To r r. & A . G ray
1
1
Psorothamnus
Rydb.
9
4
