Agriculture Reference
In-Depth Information
Figure 1.4
Longitudinal section of a typical caesalpinioid nodule, showing the characteristic blunt apex
and infected tissue with a mixture of infected and uninfected cells. In some species nodules may branch
and be lignified in the outer layers. Infected cells have bacteroids retained in fixation cells (Fig. 1.2D).
Bar
=
500
m. (Courtesy of E.K. James.)
are from South America. All, excepting herbaceous species of
Chamaecrista
, have their
nitrogen-fixing bacteria retained with modified infection threads, known as fixation
threads (Fig. 1.2D). The evolutionary implications of these aspects of caesalpinioid
legumes will be considered in Chapter 3. All nodules show indeterminate growth, are
often branched and may be quite woody. The tips of nodules are usually flattened, and
the infected tissue contains both infected and uninfected cells (Fig. 1.4).
Very little is known about the bacteria nodulating caesalpinioid legumes. The only
species in commercial use, as a forage plant, is
Chamaecrista rotundifolia,
marketed in
Australia as Wynn Cassia. The commercial inoculant for this is a broad-range strain
of
Bradyrhizobium
, CB756 (A. McInnes, personal communication).
Ch
.
fasciculata
was
the only caesalpinioid legume found to nodulate with the fast-growing, wide host
range strain NGR234 (Pueppke & Broughton, 1999). Parker (2008) found that all 20
isolates from nodules of
Tachigali versicola
were bradyrhizobia and we have evidence
that
Chamaecrista nictitans
nodules collected in the field in Brazil house a species of
Burkholderia
(E.K. James, personal communication).
1.2 Mimosoideae
In terms of genera, but not species, Mimosoideae is the smallest of the sub-families.
(Table 1.1). Former tribes Parkieae and Mimozygantheae are now included in Mimoseae
