Introduction
Tef [Eragrostis tef (Zucc.) Trotter], commonly referred to as
Teff, is an annual self-pollinated, allotetraploid (2n=4x=40) warm
season crop belonging to the Poaceae (grass) family (Assefa et al.,
2015, Costanza et al., 1979). It is a major food crop native to Ethiopia
and Eritrea for the production of a range of traditional foods and
beverages including Injera (flatbread).
Teff is a C4 plant which has high chlorophyll a/b ratios
and utilizes CO2 very efficiently during photosynthesis.
Teff is adapted to a range of growing environmental conditions (Kebede
et al., 1989). Teff grain also presents excellent storage properties.
Therefore, it plays an important role in food security in eastern Africa
and in combating global climate change (Zhu, 2018).
In recent years, Teff is becoming popular in the health-food markets of
developed countries due to its attractive nutritional properties and
gluten free nature. The inability to separate the bran from the seed
makes Teff flour rich in fiber and thua has health benefits as an
anti-oxidative and improves Hemoglobin level in the human body (Zhu,
2018, Berhe, 2018).
Despite Teff’s versatility in adapting to extreme environmental
conditions, Teff is susceptible to lodging, which can drastically reduce
yield and grain quality, and complicates harvesting (Berhe, 2018).
Lodging can limit productivity directly by reducing photosynthetic
capacity due to changes in sun/shade architecture. Lodging also limits
the use of high input Nitrogen fertilizer to boost yield.
Lodging is a process by which the shoots cereals are displaced from
vertical orientation (upright position) and settle in a permanent
horizontal position (Berry et al., 2004). It is a complicated phenomenon
that is influenced by many factors including wind, rain, geography,
landscaping, soil type, crop history, agricultural system and disease
(Berhe, 2018).
Stem lodging results from bending or breaking of the lower culm
internodes, and root lodging results from a failure in root soil
integrity (Sterling, et al., 2003). The problems of lodging can be
reduced by decreasing plant height, however, yield is reduced when
plants are shortened too much with dwarfing genes or plant growth
regulators (Berhe, 2018). Hence, it was suggested to target other traits
than height for further improvement in lodging resistance.
Teff has weak stems that easily succumb to lodging caused by wind or
rain (Assefa, 2015). Various attempts have been made to develop
lodging-resistant Teff cultivars but presently no cultivar with
reasonable lodging resistance has been obtained (Assefa et al., 2011,
Assefa, 2015). Despite lodging being the greatest cause for yield loss
in Teff, its genetic and physiological control is undertaken by
molecular breeding techniques and biotechnology (Berhe, 2018).
A lodging index can be computed as a weighted average lodging scores
according to a 0-5 scale.
Caldicott and Nuttall method (Caldicott et al., 1979) calculates the
index as follows: Lodging index = [Sum (lodging score × the relative
area for the score)] / 5.
Ethiopia is Teff’s origin and the center of its biodiversity, harboring
landraces with a wide array of phenotypic diversity, and wild
progenitors and related wild species. The genetic diversity of Teff is
represented in a collection of over 5,000 accessions (reviewed by Assefa
et al., 2015) at the Ethiopian Institute of Biodiversity. There has been
major increase in the collection size over the last decades which
demonstrates the presence of both a wide diversity of germplasm in
Ethiopia, as well as the commitment of institutes and individuals to
collect and preserve these germplasms for future use (Assefa et al.,
2015).
The genetic diversity in Teff was also discovered by using a range of
molecular markers (Zhu, 2018) and its genome has been sequenced
(Cannarozzi et al., 2014). Great genetic diversity in yield, lodging
index and stem strength related traits has been recorded in Teff (Zeid
et al., 2012).
Phenotypic variability in Teff was recorded in: grain yield, grain color
and size, days to panicle emergence, days to maturity (21 to 81 and 50
to 140, respectively), number of grains/plant (9,000–90,000), plant
height (20–156 cm), number of tillers/plant (5–35), and culm diameter
(1.2–5 mm; Assefa et al., 2001 a and b).
Teff breeding should target the improvement in the following traits:
grain yield, shoot biomass, lodging resistance, grain size and color,
grain coat properties, nitrogen-use efficiency, osmotic adjustment root
depth, tolerance to drought, salinity, and acidity, nutritional,
physicochemical, and palatability (Assefa et al., 2015). Variability for
culm internode diameter is a key factor for improved lodging resistance
(Zhu, 2018).
Overall, there is a limited amount of research on the genetic basis for
processing, palatability, and nutritional quality of Teff and its
components as food (Zeid et al., 2011). Teff variety may greatly affect
the processing, palatability, and nutritional quality of food products.
Therefore, it is necessary to assess the genetic diversity of this crop
for potential improvement of agronomic as well as food processing traits
(Zhu, 2018).
The preparation of Injera, the Ethiopian sour-dough type flat bread,
involves fermentation processes of the Teff flour (Ketema, 1993). The
fermentation preparation consists of two stages of natural fermentation,
which last for about 24 to 72 hours, depending on ambient temperatures
(Gamboa, 2008). Good quality Injera will have uniformly spaced
honeycomb-like ”eyes” or holes, and no blind spot (flat area with no
holes) on its surface. The major factor that decrease Injera quality
result from inadequate fermentation. Good quality Injera becomes soft
and pliable in texture, which enables the consumer to wrap and pick up
sauce in the Injera with fingers (Berhe, 2018). In Ethiopia, people
prefer their Injera to be white (Berhe, 2018). Texture is determined by
touch and refers to the degree of fluffiness, roughness, smoothness,
hardness or softness.
Results from the six crosses of parental lines differing in lemma color
(purple, red grey, and yellowish-white), show that at least four pairs
of genes control the inheritance of lemma color in Teff (Berhe, 2001)
with dominance complementary and epistatic gene actions. Berhe, (2001)
suggested the following model: C is a gene for basic anthocyanin color;
P1 and P2 are duplicate genes responsible for development of purple
lemma color in the presence of dominant C (Either P1 or P2 alone); p1
and p2 are genes responsible for red lemma color in the presence of
dominant C; G is gene for gray lemma color visible only when dominant C
is absent; g is gene for yellowish-white lemma color in the absence of C
and G (Berhe, 2001).
Four phenotypes of seed coat color (grain color) were documented in
Teff: dark brown, medium brown, yellowish-white, grayish-white. However,
the dark and medium brown are difficult to differentiate so they are
both included as brown. A duplicate gene pair is known to be involved in
seed color inheritance, with simple dominance and additive gene effects.
Tests of independence showed that lemma and seed color are inherited
independently (Berhe, 2001).
There is scarce documentation on seed size and seed coat in Teff (Assefa
et al., 2015). Depending on the varieties, the color of Teff grain can
be ivory, light tan to deep brown or dark reddish-brown to purple
(Assefa et al., 2015, Berhe et al., 2018). Based on people’s preference
for their consumption, white Teff is the most expensive, while in terms
of beneficially red Teff is more nutritious and gains acceptance by the
health-oriented consumers in Ethiopia and worldwide (Berhe et al.,
2018).
Different Teff varieties have different mineral concentrations. Red Teff
has a higher content of iron and calcium than mixed or white Teff
varieties, and in contrast, white Teff has a higher copper content than
the red and mixed Teff varieties (Berhe et al., 2018).
In Israel, there is a growing interest in Teff and there is a
significant Ethiopian community which is involved in the preservation of
seed resources. Several community experimental gardens exist, and the
Israeli seed bank holds a large collection of Teff lines (Ben-Zeev et
al., 2018).
In a Teff plot we found plants that looked different from the
surrounding population. First, and most striking, was the lodging
resistance presented by these single plants under the prevailing
environmental conditions compared to the surrounding plants. Secondly,
these plants, randomly distributed within the plot, were different from
the common white cultivar in stem diameter, leaf size, phenology and
inflorescence coloration. From each of these plants a single panicle was
collected for further characterization.
The objective of this study was to characterize this newly discovered
source of diversity in terms of lodging, agronomic and sensory traits.