Download Background – Tef is an important cereal crop in Ethiopia, where the

Background – Tef is an important cereal crop in Ethiopia, where the area under tef
cultivation is over one million hectares of land each year. During the 1994/95 crop
season, for instance, tef accounted for 32% of the land under cereal cultivation in
Ethiopia (Ketema 1997). While tef is resistant to a number of abiotic stresses such as
drought and heat, its optimal productivity (disease resistance and grain yield) is reached
at an altitude of 1800-2100 m, annual rainfall of 750-850 mm, growing season rainfall of
450-550 mm, and a temperature range of 10 C-27 C (50 F-80.6 F) (Ketema 1997).
Tef’s importance as a crop in Ethiopia stems from its high nutritional value. The
amino acid composition of tef is excellent, its lysine content is higher than that of all
cereals except rice and oats, it has good mineral content and its straw is nutritious for
livestock.
The fact that several putative wild tef
progenitor species of Eragrostis occur in
Ethiopia, coupled with the observation
that genetic diversity for tef exists
nowhere in the world outside of
Ethiopia, have led to the conclusion that
Ethiopia represents both the center of
origin (domestication) and diversity for
tef (Vavilov 1951). It is interesting to
note, then, that despite the high
nutritional content of tef and its broad
environmental tolerance, its cultivation
has not spread substantially outside of
Ethiopia in the time since its initial
domestication prior to 4000 BC (Ponti
1978).
The limited range of tef cultivation
outside of Ethiopia is likely the result of
many factors, but one significant
contributing factor may be the limited
productivity (i.e., grain yield) of tef outside its optimal moisture and temperature range
(note that it is most productive at higher elevations). This potential limitation to realized
tef usage sets the stage for the case study presented here.
References Cited:
Ponti, J.A. 1978. The systematics of Eragrostis tef (Graminae) and related species. PhD
Thesis, University of London, London, UK.
Seyfu Ketema. 1997. Tef. Eragrostis tef (Zucc.) Trotter. Promoting the conservation and
use of underutilized and neglected crops. 12. Institute of Plant Genetics and Crop Plant
Research, Gatersleben/International Plant Genetic Resources Institute, Rome, Italy
Vavilov, N.I. 1951. The Origin, Variation, Immunity, and Breeding of Cultivated Plants
[translated from the Russian by K.S. Chester]. The Ronald Press Co., New York.
Case Study – As a rural development worker in a northern Ethiopian highland
village, you are concerned by a trend you have observed over the past few years in your
local community: rains have become less frequent and somewhat unpredictable, and
temperatures, on average, have been slightly higher than normal. As a result, the amount
of grain produced by the local tef crop has been reduced significantly enough to warrant
some concern, as this crop represents a major protein source for your village as well as
the surrounding communities.
While on your bi-yearly trip to Addis Ababa, you meet up with your friend who
works in the University there and has just returned from a sabbatical at the International
Plant Genetics Resources Institute. You describe the situation to her, and you both agree
that with global climate change becoming more and more of a reality, the trend you have
been witnessing may be part of a more permanent emerging temperature and rainfall
pattern. With this in mind, your friend begins discussing possible solutions to the
problem of decreased tef grain yield.
Can you devise a possible strategy for a research program aimed at improving the
performance of tef under novel (hotter/drier) climatic conditions? What questions will
you and your friend need to answer to address this problem? What additional
information on tef (or other plants) will you need?
Since your village, at 1500 m, is already at the lower end of the optimal elevation range
for tef, it may not be possible to increase the grain yield by introducing a different tef
variety. Your friend suggests that it may be possible to genetically manipulate tef in
order to produce a variety that will be able to withstand higher temperatures and lower
rainfall: Eragrostis, the genus that tef belongs to, has some close relatives that are
desiccation tolerant and occur in very hot, dry areas in Tanzania and Kenya. At least one
of these species has been studied to identify some of the major genes involved during its
response to desiccation. Perhaps it would be possible to identify homologous
(evolutionarily related) genes in tef and engineer tef plants that produce more of those
genes’ products (proteins) under heat and drought stress.
During the rest of your visit to the capital city, you and your friend put together the
resources you’ll need to identify candidate genes for increased stress tolerance in tef:
What types of resources might you need?
A research paper on the evolutionary relationships of tef and a paper on the desiccation
tolerant relative; projected distributional maps (based on environmental niche models) for
tef, its wild progenitor, and the desiccation tolerant relative; and a list of online resources
for DNA sequence data. With these tools, you can identify genes in tef that have the
potential to increase its stress tolerance. After you have identified these genes, your
friend will be able to begin experiments with targeted gene manipulation in her
laboratory.