«Eragrostis tef(Zucc.) Trotter Seyfu Ketema Biodiversity Institute Addis Abeba, Ethiopia 2 Tef. Eragrostis tef (Zucc.) Trotter The International Plant ...»
Among cereals, tef straw is relatively the best and is comparable to a good natural pasture. The same source indicated that the performance of animals on residue diets is also known to vary depending on the crop species. The highest daily weight gain was obtained using tef straw. Table 4 shows the weight gains of steers fed for 116 days on a ration composed of 50% residue, 20% molasses, 25% niger cake (Guizotia abyssinica), 4% bonemeal and 1% salt (IAR 1975). Dry-matter intake and daily weight gain were lowest for wheat straw, 5.0 kg and 352 g/head respectively. Daily feed intake was the highest for tef.
According to Burt-Davy (1913), the chief value of tef as a hay crop lies in its palatability, high nutritive value, narrow albumin ratio (for a grass hay), high yield, rapid growth, drought resistance and ability to smother weeds. In South Africa tef is grown as a forage crop. According to Taddesse (1969), tef produces more than 18 Tef. Eragrostis tef (Zucc.) Trotter Table 4. Weight gains of steers fed on crop residue-based diets for 116 days, Holetta (1974/75) (Lulseged and Jemal 1989, citing IAR 1975)
twice as much forage as weeping lovegrass (Eragrostis curvula), producing an average of 14.5 t/ha of green material in 3 months. This again shows that tef has a great potential to serve as a forage crop. Hence it can be used as a dual or multipurpose crop, i.e. for both cereal and forage.
Tef straw costs 40-50 Ethiopian birr/l00 kg (6 Ethiopian birr = US$l), while the price of wheat straw is 30-40 Ethiopian birr/l00 kg in Ada region. The national average grain yield of tef is nearly 1 t/ha. With a national average of total biomass production of 4.1 t/ha and a harvest index of 24.4% on 1.38 million hectares of land the country produces 4.3 million tonnes of tef straw annually. The price of tef straw varies depending on region as well as season. However, taking the price in Ada region as a base price, it is possible to roughly estimate that nationally the price for tef straw is between 129 and 172 million Ethiopian birr annually. Both the amount of tef straw produced as well as its price clearly indicate the important role that tef straw plays as a crop-residue livestock feed in Ethiopian agriculture.
19 Promoting the conservation and use of underutilized and neglected crops. 12.
6 Genetic resources Existing genetic variation As part of the routine characterization programme of germplasm at PGRC/E, Dawit and Hirut (1995) characterized 506 tef accessions (13%) of the total collection for some morpho-agronomic characteristics. Frequency of occurrence of some qualitative characters in tef is presented in Table 5. Fifty-four percent of the 506 collections showed an intermediate type of panicle and 21% were a fairly loose type. Extremely compact and semi-compact panicle types were observed on 13 and 9% of the accessions, respectively. Among the characters, light colours of panicle, glume and seed appeared to be dominant. Concerning glume hairiness, low level of hairiness w a s f o u n d t o b e d o m i n a n t. Variability of some agronomic characters of tef germplasm was found to be high (Table 6).
Table 5. Frequency of occurrence of some qualitative characters of 506 tef accessions (Dawit and Hirut 1995)
Apart from the studies made at the PGRC/E, Seyfu (1993) characterized 2255 pure line accessions of tef germplasm for 15 morphological and agronomic traits.
All the traits studied showed a wide magnitude of variation and had statistically significant differences. This elucidates the existence of a great wealth of genetic diversity in tef which could be utilized in the improvement programme of the crop (Table 7).
Table 7. Descriptive statistical values for phenological traits, components of height, shoot biomass, harvest, index, flag leaf area and culm thickness for 2255 pure line accessions of tef (Seyfu 1993)
† Data taken for 100 germplasm accessions ‡ Data from 45 germplasm accessions.
Out of the 15 traits studied, maximum genetic diversity was observed in the flag leaf area, grain yield per plant and straw yield per plant.
Wild relatives of cultivated crops play an important role as sources of useful and transferable genes. They enrich and broaden the available genetic base in crop improvement programmes and assist in developing superior genotypes. Thus, the wild relatives of tef should be considered for improvement work, identified, collected, conserved, characterized and utilized. So far, no systematic collecting or any activity related to the germplasm of the wild relatives of tef has been conducted by PGRC/E. Several studies were made to identify the wild Eragrostis species that Promoting the conservation and use of underutilized and neglected crops. 12. 21 are related to tef (Costanza 1974; Endeshaw 1978; Ponti 1978; Tavassoli 1986).
However, there are no study results which identified specific economically important traits such as tolerance to diseases, drought, waterlogging or low temperature in the wild Eragrostis species, and thus no recommendations have been made for an interspecific hybridization programme. Only Endeshaw (1978) studied the protein content of 11 cultivars of tef and 14 Eragrostis species and stated that the accessions of tef were lower in total protein content than that of other wild Eragrostis species.
Thus, he suggested the possibility for improving the protein content of tef through an interspecific breeding programme.
Several attempts were made to investigate the possibility of crossing tef with other wild Eragrostis species. However, the attempt to make a cross between E. tef and E. curvula was not successful. Also, interspecific hybridization attempts using three tetraploids, i.e. E. tef x E. cilianensis (4x); E. tef x E. pilosa (4x); and E. tef x E. minor (4x) were not successful (Tavassoli 1986). Some barrier to gene exchange was suspected where it was not possible to develop a plant from the hybrid seed formed by crossing E. tef with E. minor (Tavassoli 1986).
Conservation The Plant Genetic Resources Centre of Ethiopia (PGRC/E), now called the Biodiversity Institute, is actively engaged in collecting, conservation and characterization. Utilization of the germplasm for the tef improvement programme is mainly done in cooperation with the Institute of Agricultural Research. Currently the PGRC/E has a total of 3842 accessions of tef out of which 187 accessions are repatriations, 357 selections, 1310 accessions collected by other institutes and 1988 accessions collected by the PGRC/E. The passport data for the materials collected by the PGRC/E include accession number, collection number, local name, place of collecting, longitude, latitude, altitude, period of collecting and sample type. Other institutions maintaining duplicate accessions of tef germplasm are the Institute of Agricultural Research and the Debre Zeit Agricultural Research Centre. Few accessions are kept outside Ethiopia. The FAO - World Information and Early Warning System on Plant Genetic Resources reports the major ones as follows: 368 accessions kept at Western Region Plant Introduction Station USDA-ARS, Washington State University; 341 accessions kept at the National Seed Storage Laboratory USDA-ARS, Colorado State University; 30 accessions kept -at the Department of Genetic Resources, Japan, and 30 accessions kept at the Institute of Crop Science, Germany (Table 8).
In a study conducted by Zewdie and Ellis (1991a), regarding the upper-moisturecontent limit to negative relations between seed longevity and moisture in niger and tef, they concluded the following. Increase in seed moisture content above 22.1% and 24.1-27.7% moisture content (fresh weight basis) had little or no effect on seed longevity (time taken for normal germination to decline to 50%) in one seedlot of tef when stored hermetically at 20°C. These estimates of the upper limit to negative relations between longevity and moisture content in air-dry storage are equivalent 22 Tef. Eragrostis tef (Zucc.) Trotter Table 8. Institutions with collections of tef germplasm (FAO - World Information and Early Warning System on Plant Genetic Resources. 1995, updated)
† For full addresses see Appendix II.
‡ nd = no data, the institution did not provide the information; sample: F=freely available, R=restricted.
§ Passport data: A=available.
Storage: L=long-term storage, M=medium-term storage, S=short-term storage, F=field collection.
to seed water potentials of about -14 MPa and -20 MPa to -16 MPa, respectively In another study made by Zewdie and Ellis (1991b), on the survival of tef and niger seeds following exposure to subzero temperatures at various moisture contents, they concluded that tef seeds stored at 4.4-22.9% moisture content showed more than 96% normal germination through storage at -18°C. In contrast, some 75% of those at 26.1% moisture content failed to germinate following exposure to -18°C, with no further damage to germination occurring during the following 100 days of storage.
The germination of seeds of tef at 22.5 and 24.4% moisture content was reduced to 92 and 10%, respectively, following immersion in liquid nitrogen for 3 days. In addition, a smaller effect of liquid nitrogen storage was detected at lower moisture contents by probit analysis, normal germination being reduced from 99.1 to 98.1%.
This decline in germination for tef seeds stored in liquid nitrogen for 3 days at 4.4moisture content was significant (P0.005), but neither an effect of seed moisture content was detected within this range (P0.25) nor was there a significant interaction between the effect of seed moisture content and liquid nitrogen storage (P0.25).
At the PGRC/E tef germplasm is conserved ex situ using a cold store. Tef seeds are dried to a level of 3-7% moisture content and then stored in laminated aluminium Promoting the conservation and use of underutilized and neglected crops. 12. 23 foil bags at -10°C for long-term storage and at 4°C for short- and medium-term storage. Duplicate tef germplasm samples at the other institutes are kept in bottles at room temperature and rejuvenated every 3 years.
The accessions that are currently conserved at the PGRC/E are from altitude ranges of 950 to 2950 m asl. No samples were obtained from altitudes below 950 and above 2950 m asl. Figure 4 shows the distribution of samples over different altitude ranges, while Figure 5 shows geographical distribution of collected tef accessions. The highest number of collections came from altitudes ranging from 1750 to 1950 m and 1951 to 2150 m (temperature 15-20°C, annual rainfall 900mm), the least were from 950-1150 m (20-28°C, 350-900 mm) and 2750-2950 m (l0-15°C, 900-1800 mm) (Dawit and Hirut 1995).
25 18.78 16.48
Gaps in collections and recommended plan of action The following points are among some of the major gaps in the present tef germplasm work and the collection held at the PGRC/E. Most of the accessions held at the PGRC/E were acquired before the establishment of PGRC/E; hence they were not collected in a systematic way - following appropriate sampling procedures and taking into consideration various ecogeographic regions and environments of special interest. Over 55% of the accessions lack adequate passport data details. Thus, it is not possible to make correlation studies with the environment or other factors. In addition, the accessions at the PGRC/E have not been adequately characterized for several traits of economic importance such as tolerance to drought, waterlogging, high and low temperatures in order to be useful for the tef improvement programme.
So far no collecting of the wild relatives of tef has been done. The system for germplasm data storage, retrieval and dissemination needs improvement, through updating the software and hardware used within the PGRC/E as well as generally improving the germplasm information system within the country.
The following points could be taken into consideration in a plan of action. The study made on the 2255 accessions of tef for 15 morphological and agronomic traits has indicated the availability of significant genetic diversity, thus demonstrating the high potential that exists for the improvement of tef (Seyfu 1993). Improvement could be achieved through direct selection out of the existing 2255 pure line accessions or by effecting gene recombination between parental lines selected from them, to create genetically superior cultivars through conventional breeding or biotechnology techniques, if they are made available for tef in the future. Thus, further characterization and evaluation work on the established line is necessary for additional economically important traits, to develop genetically superior cultivars.
Other activities to be considered are:
Determining the geographic distribution of the wild relatives of tef within the country Assessing the genetic diversity of tef both within and between regions with regard to morpho-agronomic and molecular characteristic, to effectively utilize the germplasm.
Making systematic collections with comprehensive passport data, taking into consideration various ecogeographic regions and targeted environments of specific interest.
Making ethnobotanical studies to find out more about the crop.
Further characterization and evaluation of the existing accessions fo economically important traits such as tolerance to drought, waterlogging, diseases, insects, etc.
Updating and making efficient the information system on tef germplasm.
There are no major constraints noted so far in the ex situ conservation of tef. Both the total number of improved varieties released so far (only eight) and the amount of improved seed distributed to farmers each year are low. Most farmers (80%) use their own landraces as their seed source for production. Thus, one could say that 26 Tef. Eragrostis tef (Zucc.) Trotter tef is currently being conserved on-farm by farmers. The use of landraces will diminish in the future with the modernization of agriculture and the wider use of improved cultivars. In addition, other sources for genetic erosion such us drought, population growth, habitat destruction and environmental degradation will result in changing the existing farming system and have a negative impact on the genetic resources of tef. Thus, as the need arises in the future in situ conservation should be considered.