Trigonella breeding biology — playing home or
away
How does one establish breeding programmes for
crop species that have, so far, received little attention? That question lies
behind the work of Nair et al. (Adelaide, Australia,
pp. 883–888). They have worked on Trigonella balansae, a Eurasian legume that is capable of productive growth in alkaline soils
in areas that receive less than 400 mm annual rainfall. The authors point out
that this makes T. balansae potentially useful in temperate
zones of Australia.
Further, it is readily nodulated by local strains of Rhizobium meliloti
and thus could complement or even replace Medicago
species in some farming systems. However, before any breeding to
improve performance is undertaken, the characteristics of the plant’s breeding
system must be established. This was the aim of the work presented in this
paper. The study included an investigation of floral morphology, a comparison
of non-self with self-pollination, the role of vectors in pollination and the extent
of inbreeding depression. The species is completely self-fertile, with a relatively
low level of inbreeding depression, but selfing cannot occur in the absence of
vectors because of the spatial arrangement of anthers and stigma at the time of
anthesis. However, vectors such as bees are able to effect the
transfer of both self and non-self pollen to receptive stigmatic surfaces. The
breeding system is thus described as mixed but the authors suggest that it is
likely, because of the structure of the florets at the time of anthesis, for
there to be a greater tendency to outbreeding. This suggestion is supported by
their measurement of the actual selfing rate. This paper thus represents clear
progress in understanding the breeding system in a potential new crop. However,
the authors’ cautious final statement is that this study of one population
cannot be used to generalize about the whole species. There is more work still
to be done.
Professor J. A. Bryant
University of Exeter, UK
j.a.bryant{at}exeter.ac.uk
