«Eragrostis tef(Zucc.) Trotter Seyfu Ketema Biodiversity Institute Addis Abeba, Ethiopia 2 Tef. Eragrostis tef (Zucc.) Trotter The International Plant ...»
The transient expression of the ß-glucuronidase (GUS) gene in embryogenic callus and the antibiotic sensitivity of cultured tissues of tef to Kanamycin and Gentisin (antibiotics), which lays a foundation for the future selection of transgenic tef using these markers, was studied (Tesfaye 1991). Introduction of a foreign gene through the incubation of seeds with plasmid DNA for various lengths of time was not successful for tef.
Nugent and Gaff (1989) reported electrofusion of protoplasts of tef and other desiccation-resistant species in the genus Eragrostis. Protoplasts were obtained by enzymatic degradation of the cell wall from desiccation-tolerant ‘resurrection grasses’ (Eragrostis and Sporobolus spp.). The highest protoplast yield was achieved by using young tissue of leaves still enclosed in the sheaths of older leaves.
Electrofusion was successfully applied to achieve fusion between protoplasts of desiccation-sensitive and tolerant species (S. pyramidalis and S. pellucidus, E. tef and either E. hispida or E. paradoxa and between two desiccation-tolerant species (E. invalida and E. nindensis).
Wide hybridization between related but distinct species normally fails because of fertilization, embryo lethality or disruption of embryo-endosperm relations (Simmonds 1979). If embryo-endosperm relations is the block, then embryo culture can be very valuable, and indeed such embryos of several plant species have been rescued. Interspecific crossing of tef with related wild species requires the support of this technique.
Protoplast fusion has long been proposed as an innovative and extensive method for producing hybrid plants that cannot be obtained by sexual means. The best use of protoplast fusion will be in the production of hybrids which contain the nuclear and cytoplasmic genome of one parent and only the cytoplasmic genome of the second parent (Vasil 1983). These can be of particular advantage in the transfer of cytoplasmic male sterility, an important trait in breeding, as yet not discovered in tef.
The development of rapid screening techniques for identifying germplasm with economically important traits such as tolerance to drought, waterlogging, low Tef. Eragrostis tef (Zucc.) Trotter 32 temperature, etc. will be essential for the optimum utilization of the germplasm and the development of superior genotypes.
Currently there are neither sufficient basic and applied research results in tef biotechnology to be put to practical use in the improvement of tef nor are there sufficient funds to indulge in large-scale tef biotechnology research, and thus conventional breeding remains the appropriate. option to improve the crop.
33 Promoting the conservation and use of underutilized and neglected crops. 12.
8 Production areas Within Ethiopia the administrative regions of Shewa, Gojam, Gonder Wello and Welega are the major tef-production areas. It is widely grown in both high-potential and marginal production areas. These areas include most parts of the Vertisols that suffer from waterlogging and other non-Vertisol parts of the country that suffer from low moisture stress. Tef is grown in almost all regions of the country for home consumption since it is a preferred grain, and for local market since it fetches the highest grain price compared with other cereals and is used as a cash crop by farmers.
A small amount of the tef produced for local markets is also exported. No specific production areas are targeted for export. Major and minor tef-production areas in Ethiopia are presented in Figure 6.
Table 9 shows the production of tef in relation to other crops in Ethiopia. The average annual production is estimated to be 1.38 million tonnes. With an average grain price of 2000 birr/t the average annual trade value of tef could be estimated to be 2.76 billion birr or US$460 million at the 1995 rate of exchange (6 birr = US$l).
Outside Ethiopia, small-scale tef grain production has started in the USA and Canada. Approximately 200 acres of tef are grown commercially by Wayne Carlson in Idaho (National Research Council 1996).
Table 9. Area under cultivation, yield and production of major crops in Ethiopia
9 Ecology Tef is adapted to a wide range of environments and is presently cultivated under diverse agroclimatic conditions. It can be grown from sea level up to 2800 m asl, under various rainfall, temperature and soil regimes. However, according to experiences gained so far from national yield trials, conducted at different locations across the country, tef performs excellently 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. A very good result can also be obtained at an altitude range of 1700-2200 m and growing-season rainfall of 300 mm.
According to experiences from Debre Zeit, which is one of the best tef-growing regions known for its production of the best preferred and high-quality tef called ‘magna tef’ (DZ-O1-196) as well as for its high production level per unit area of different varieties of the crop, tef suffers less from diseases, gives better grain yield and possesses higher nutrient contents, especially protein, when grown on Vertisols rather than on Andosols. However, proper management on Vertisols calls for using different seedbed preparation methods to overcome the problem of poor stand establishment that is encountered either because of soil crusting and cracking during growing seasons with low moisture stress or because of waterlogging during very wet growing seasons. This problem can partially be alleviated by using better practices such as packing the seedbed during the dry season and making drainage furrows during the wet season, as well as other cultural practices such as determining sowing dates.
Tef is sensitive to daylength, since its vegetative and flowering habits were found to be affected when plants of the same lines grown in Ethiopia were grown during the summer and the winter in England (Seyfu 1983). The plants performed best in Ethiopia, where there is approximately 12 hours of daylight. When the same cultivars were grown in England in heated glasshouses during winter under short-day conditions (ca. 8 hours), their height was very short, around half their size when grown in Ethiopia. Flowering also was greatly affected: the flowers remained open for longer periods, most of the anthers never produced pollen grains, and seedset was extremely low, perhaps because many florets became male-sterile. Their vegetative stage was lengthened and they took more than 6 months to reach maturity.
The number of florets per spikelet was greatly reduced. The summer-grown plants in England were affected by long day conditions (ca. 16 hours); however, much less than the winter grown plants. The plants grew taller, they had a longer vegetative period, but not as long as the winter-grown ones. Flower opening was not much affected, but the number of sterile flowers compared with the ones grown in Ethiopia was high, but lower than the English winter-grown ones, and there were many spikelets where more than one floret opened on the same day. The number of florets per spikelet was more or less the same as the ones grown in Ethiopia but the seedset was somewhat lower (Seyfu 1983).
36 Tef. Eragrostis tef (Zucc.) Trotter 10 Agronomy In Ethiopia tef is cultivated in much the same way as wheat and barley. Depending on the location and maturity period of the cultivar it is grown during the main growing season between July and November, and also during the small rainy season between March and June. It is mainly cultivated as a monocrop, but occasionally under a multiple cropping system. In such cases it is usually grown as an intercrop with rapeseed (Brassica napus), safflower (Carthamus tinctorius) and sunflower (Helianthus annuus) or relay-cropped with maize (Zea mays) and sorghum (Sorghum bicolor). It is also cropped sequentially in a crop-rotation system in the mid- and high-altitude areas after chickpea (Cicer arietinum), field pea (Pisum sativum), faba bean (Vicia faba) and grass pea (Lathyrus sativus); while at low-and some mid-altitude areas it is ‘grown after haricot bean (Phaseolus vulgaris). Usually a 4-5 year rotation
cycle is practised. In a 4-year rotation cycle the sequence followed would be:
pulse/tef/tef (or another cereal, for example, wheat or barley)/pulse. In a 5-year rotation cycle the sequence would be: pulse/tef/tef/other cereal/pulse.
Seedbed preparation and sowing Under current farmers’ practices, a tef field is ploughed two to five times depending on the soil type, weed conditions and waterlogging. Heavy clay soils need ploughing more frequently than loam or sandy soils. Fields with high weed populations receive more ploughings than those with fewer weeds. Vertisols in areas where there is a problem of waterlogging are ploughed more than those without, to open drainage furrows. Traditionally, farmers alleviate the problems of waterlogging through preparing a raised seedbed, similar to a cumber-bed, by a hand-or oxen-pulled broad bed maker after the land has been well ploughed. The fourth and fifth ploughings are usually made for opening drainage furrows; the last is called derdaro.
In a study conducted to evaluate effect of tillage and weed control practices on yield and yield components of tef, it was reported that ploughing more than once may not be necessary provided nonselective herbicides are applied to control weed flush before ploughing, suggesting that tef can be produced under reduced tillage.
In this study, although nonselective herbicides were applied before ploughing, it was found that additional weeding (hand or chemical) once at the early tillering stage of tef increased yield (Aberra 1992).
Under the current farmers’ production system, tef seeds are sown on the surface of the soil and left uncovered or sometimes covered very lightly by pulling woody tree branches over the field using oxen. It has been observed that covering tef seeds thinly or pressing them lightly just after sowing or packing the seedbed before sowing under moisture stress conditions promotes germination and increases grain yield through increasing stand establishment on both Andosols (light clay loam soils) and Vertisols (heavy clay soils). Particularly if there is moisture stress or rainfall interruption incidence at the beginning of the growing season, moderate packing of the seedbed is useful to enhance stand establishment on Vertisols that suffer from soil crusting. Farmers pack the seedbed using oxen, donkeys, goats, sheep and other 37 Promoting the conservation and use of underutilized and neglected crops. 12.
farm animals. Seedbed packing is done before sowing tef to make the seedbed firm, prevent the soil surface from drying quickly, assist germination of seeds and minimize the damaging effect of low moisture during late onset of rain. Packing of the seedbed is also practised to free the seedbed from weeds by turning them tinder.
Otherwise, during years of sufficient rainfall, in areas where sometimes there is a shortage, or in areas where there always is a reliable and sufficient amount of rainfall with good distribution, packing the seedbed does not have any additional positive advantage in promoting germination and stand establishment.
In a study conducted to investigate the effect of planting depth and soil type on germination and emergence of tef, using two tef cultivars (DZ-01-354 and Dabi), it was observed that emergence from surface planting and from greater than 20 mm depth was significantly lower than either 5, 10, 15 or 20 mm depth. There was no significant difference between crop emergence from 5 and 20 mm depths. Plant height was not affected by a planting depth of between 5 and 15 mm. However, seedlings that emerged from surface and planting depths of greater than 15 mm had significantly reduced height while seedlings that emerged from clay loam were taller than those from sandy loam (Aberra 1992).
Tef can be sown during a season when the rainfall is reliable and well distributed.
For most cultivars, 300-500 mm of rainfall per growing season is adequate. Early maturing varieties (60-75 days) can do with less than 300 mm of seasonal rainfall.
Tef germinates and establishes faster on Andosols than on Vertisols.
About 15-55 kg of tef seeds are sown per hectare under different conditions. If a manually or motor-driven broadcaster or drill is available, a lower seed rate (about 15 kg/ha) is recommended. If sowing is to be done by hand-broadcasting, it would be difficult to evenly distribute the 15 kg/ha of seeds because of the small seed size – l000-seed weight is only 265 mg. Therefore, 25-30 kg/ha seeds are recommended for broadcast sowing. Farmers’ traditional practice is to broadcast tef at the rate of 40-50 kg/ha.
Fertilization Systematic studies on the fertilizer requirements of tef under varying conditions and in various regions need further investigation. However, currently the following
recommendations are made:
Recommendations from Debre Zeit Agricultural Research Centre: On heavy clay
soils (Vertisols): 60kgN and 26kgP2O 5 per ha. On sandy clay loam soils (Andosols):
40kgN and 26P 2 O 5 per ha. Urea is generally recommended to be applied in split applications.
Alkämper (1973) has made the following conclusions regarding the response of
tef to fertilizers:
High rates of fertilizers can be applied at sowing together with the seeds on the bare land without any harm to the germination rate of tef.
Nitrogen produces more straw while phosphorus encourages good grain production.
38 Tef. Eragrostis tef (Zucc.) Trotter Potassium is of minor importance to tef production.
The figures concerning the uptake of the main elements by tef are relatively low.
Split applications of nitrogen may result in increases in grain yield without influencing the straw yield.
Weeding It is best to start with a weed-free and clean field that has been ploughed in the appropriate season and frequently enough to kill the weeds. The work should also start with clean tef seeds that are free of weed seeds. Hand-weeding once at early tillering stage (25-30 days after emergence) is ideal and adequate, if the weed population is low. However, if the infestation is high, a second weeding should be done at the stem-elongation stage. On the other hand, hand-weeding after heading is not recommended, since it may result in heavy damage to the plants.