Agriculture Reference
In-Depth Information
unusual feature is that
Pentaclethra
, which has three species, has at least one that can and
one that cannot nodulate. There are many negative reports for
P. macrophylla
(African)
and several positive reports for
P. macroloba
(South American). There are no reports for
the third species,
P. eetveldeana
(African). Of the other non-nodulating mimosoid genera,
most are African. As several of the genera whose nodulation status is unrecorded are
grouped with known non-nodulating genera, it is likely that the proportion of non-
nodulating genera will increase. Where they stand in possible evolutionary terms will
be discussed in Chapter 3.
The largest genus in Mimoseae is
Mimosa
, with over 500 species, of which 115 are
now known to nodulate (Elliott et al., 2008). Many of these nodulate with
-rhizobia
(
Burkholderia
and
Cupriavidus
), rather than
-rhizobia, a topic that will be discussed
further in Chapter 4. Elliott et al. (2007a) looked at the ability of genera related to
Mimosa
to nodulate with
-rhizobia and found no coherent pattern. The next largest
genus,
Prosopis
, nodulates with a variety of
-rhizobia, but some species can also use
-rhizobia (James et al., unpublished data). Many of its species are highly drought
and salinity tolerant and have interesting physiological properties such as bringing up
water from deep in the soil (hydraulic lift). These properties are considered in Chapters
2and5.
Neptunia
has been quite widely studied because of the aquatic habitat of many
of its species. Its species nodulate with a range of
-rhizobia (Chapter 4) from different
genera.
1.3 Papilionoideae
Papilionoideae is the largest and most complex of the three sub-families. For the present
purpose, it has been subdivided on characteristics related to nodulation, nodule struc-
ture and nodule physiology. Fig. 1.5 outlines the major groups.
1.3.1 Non-nodulation in the Papilionoideae
As with Mimosoideae, some genera appear never to have had the ability to nodulate,
whilst in others this ability may have been lost (as in some species of
Acacia
, sub-genus
Aculeiferum
). This section will deal with genera thought to be in the first category.
Three tribes of papilionoid legumes contain genera that appear to be unable to
nodulate, namely Dipterygeae, Sophoreae and Swartzieae (the non-nodulating branch
coupled to the nodulating Swartzia group in Fig. 1.5). The last two of these tribes also
contain nodulating genera, and these are listed in Table 1.6. Tribe Swartzieae currently
consists of 17 genera, but this number is likely to change as it is known not to be mono-
phyletic and was even once thought to belong in the Caesalpinioideae. Of the 13 genera
not listed in Table 1.6, there is no information on four, one (
Bocoa
) has mixed reports,
with the remaining eight (
Aldina, Amburana, Baphiopsis, Cordyla, Exostyles, Harleyo-
dendron, Mildbraediodendron,
and
Zollernia
) having good evidence of non-nodulation
(Sprent, 2001). The latter group has a total of 41 species. Ireland (2005) put the
four nodulating genera, together with
Bocoa, Candolleodendron
and
Trischidium
,inone
