Abstract:
Advances have been recently made in the breeding and characterization of three
major legume crops of the semiarid tropics, chickpea, pigeon pea, and groundnut.
However, other wild-growing
legumes, called “orphan legumes,” with potential as
crops, but are not yet cultivated would benefit from further attention. This review
considers the domestication of one such plant, marama bean (Tylosema esculentum).
Marama has long been recognized as a potential crop particularly for southern Africa,
but coordinated, long-term
research and development has been lacking. Marama is a
perennial, outcrossing hexaploid, growing under extreme conditions in a restricted
geographic range; only natural stands exist that are likely to be overexploited.
Marama has two potential units of economic yield, seed and tuber. The seed is protein-
and
oil-rich,
with potential in the pharmaceutical and cosmetic industries while
the tuber is high in carbohydrates. In this review, the different aspects of bringing a
wild plant into cultivation are considered, together with the additional socioeconomic
benefits of developing a breeding program. An international collaboration is analyzing
aspects of the plant structure and physiology, molecular biology, and its interactions
with environment with a view to developing marama as a crop, with a role in
food security, that could be harvested by local communities. Molecular topics considered
include next-generation
sequencing for developing molecular maps, genotyping
by sequencing, identification of quantitative trait loci for important agronomic
traits, protein quality, and incompatibility mechanisms. To achieve domestication
requires seed gardens and fields, and the phenotyping of marama material from different
locations. Community engagement will also ensure agronomic sustainability
and farmer participation. This review describes an approach for a successful outcome
of a breeding program to introduce improved marama and highlights the challenges
in achieving this, which is a paradigm for the difficulties in the cultivation of “orphan
species.”
