Agriculture Reference
In-Depth Information
Tab l e 1 . 11
(
Continued
)
Genus
Species
Nod.
Platymiscium
Vogel
19
6
Platypodium
Vogel
2
1
Pterocarpus
Jacq.
3
40
18
Ramorinoa
Speg.
1
?
Riedeliella
Harms
3
1
Stylosanthes
Sw.
25
21
Tipuana
(Benth.) Benth.
1
1
1
About 16 of these are able to form nodules on stems as well as roots.
2
This Madagascan genus is thought to be extinct.
3
Brazilian species appear unable to nodulate.
endemic to the Cape region of South Africa. Nothing is known of its nodule structure.
Tribes Mirbelieae and Bossiaeeae (Table 1.12) are Australian, with some Mirbelieae ex-
tending into south Papua New Guinea. Their taxonomy has been extensively studied,
but their nodulation and nodule characteristics are only now beginning to be under-
stood. Nodules in both tribes are indeterminate, often branched. A wide variety of fast
and slow-growing
-rhizobia can nodulate them, the exact species often depending
on soil pH (Lafay & Burdon, 1998; Thrall et al., 2000). Nodule structure in
Aotus erici-
folia
shows infected tissue to contain both infected and uninfected cells and infection
threads are seen (Lawrie, 1981) This does not necessarily mean that there is a root hair
infection pathway (Sprent, 2007). Most genera are found in dry, often arid areas, in
soils of very low fertility, a point which will be discussed in Chapter 2.
Viminaria
is
unusual in that it is found in seasonally flooded soils and has negatively geotropic
roots (pneumatophores) as well as cluster roots (Walker et al., 1983). These tribes have
recently (
5 Ma ago) diversified into arid areas (Chapters 2 and 3) and the charac-
teristics that enable them to nodulate in environments that are generally regarded as
unsuitable are urgently in need of study. Unfortunately, funds for studying nodula-
tion in Australia (and in other countries) are targeted towards potential agricultural
species. Members of these tribes may be toxic to grazing animals, with some species
of
Gastrolobium
, for example, producing large quantities of fluoroacetate (Mead et al.,
1985). Some populations of red kangaroos have co-evolved to cope with this.
∼
1.3.6 The Millettioid clade
The Millettioid clade in Lewis et al. (2005) has three branches, first tribe Indigofereae,
second Abreae
Psoraleae. These
branches will be considered in turn. Indigofereae has seven genera (Table 1.13), with
the pantropical
Indigofera
being the third largest genus in Leguminosae. Although
most species are African and Madagascan, considerable numbers are also found in
Asia and Australia, with a few in the New World. Nodules are indeterminate and
often branched, although
Indigofera linifolia
nodules when young appear desmodioid,
+
Millettieae, and third Desmodieae
+
Phaseoleae
+
