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.