CONTRACT NUMBER: ICA4-CT FINAL REPORT

Transcription

1 INCO-DC: International Cooperation with Developing Countries CONTRACT NUMBER: ICA4-CT FINAL REPORT Start date: 01 October 2000 Duration: 36 months Increasing the Productivity of Bambara Groundnut (Vigna subterranea (L.) Verdc.) for Sustainable Food Production in Semi-Arid Africa Project homepage: Keywords: Bambara groundnut, Vigna subterranea, Semi-Arid Africa Shared-Cost RTD Contract number: ICA4-CT

2 TITLE: Increasing the Productivity of Bambara groundnut (Vigna subterranea (L.) Verdc.) for Sustainable Food Production in Semi-arid Africa COORDINATOR UNIVERSITY OF NOTTINGHAM SUTTON BONINGTON CAMPUS SCHOOL OF BIOSCIENCES DIVISION OF AGRIC AND ENV SCIENCES LOUGHBOROUGH, LE12 5RD LEICESTERSHIRE, UK DR SAYED AZAM-ALI Tel : Fax : CONTRACTORS BOTSWANA COLLEGE OF AGRICULTURE DEPARTMENT OF CROP SCIENCE AND PRODUCTION PRIVATE B GABORONE BOTSWANA DR ELENIMO KHONGA ebkhonga@bca.bw Tel : Fax : TECHNICAL UNIVERSITY MUNICH CHAIR FOR AGRONOMY AND PLANT BREEDING ALTE AKADEMIE FREISING-WEIHENSTEPHAN GERMANY MAHANENE RESEARCH STATION OMUSATI REGION UUTAPI CONSTITUENCY P.O. BOX 646 OMBALANTU NAMIBIA UNIVERSITY OF SWAZILAND DEPARTMENT OF BIOLOGICAL SCIENCES FACULTY OF SCIENCE P/B4 KWALUSENI SWAZILAND PROF. DR. G. WENZEL schenkel@wzw.tum.de Tel. : Fax : MR KLAUS FLEISSNER saromahe@iway.na Tel : Fax : none PROF ABU SESAY Asesay@africaonline.co.sz Tel : Fax : Or :

3 ABSTRACT This report describes a multidisciplinary research project carried out by five academic and research institutions from Africa and Europe with the aim of increasing the productivity of bambara groundnut (Vigna subterranea (L.) Verdc.) for sustainable food production in semi-arid Africa. Collaborating institutions were Botswana College of Agriculture, Botswana; the University of Nottingham, UK; the Ministry of Agriculture, Water and Rural Development, Namibia; Technical University of Munich, Germany and the University of Swaziland, Swaziland. A notable feature of this research project was the emphasis on incorporating indigenous knowledge and preferences of local growers and consumers of bambara groundnut in the research process. A significant finding of the surveys of local growers was that most of the preferences (high yield, large seeds, early maturity and fast-to-cook) expressed by farmers, for a bambara groundnut ideotype, were common among the African countries. One implication of this finding is that a single strategic breeding programme could meet the crop improvement needs of all three countries. Genetic and agronomic characterisation of nine bambara groundnut landraces in the field and in controlledenvironment glasshouses showed that the performance of these landraces was mostly affected by the amount and distribution of rainfall. The best yields ( kg ha -1 ) were obtained in Swaziland where the average total rainfall ranged from 633 mm to 728 mm and lowest yields were in Botswana ( kg ha -1 ) where the rainfall ranged from 389 mm to 433 mm. Genetic variations in the response to drought were evident, thereby offering an opportunity for crop improvement based on the existing genetic variation. Investigations on the genetic diversity of bambara groundnut showed that landraces consisted of three to eight major different genotypes. Furthermore, accessions from neighbouring countries were clustered together but no pure clusters composed of accessions from a single country were observed. Participatory development of a simple and feasible marker technology for genetic diversity studies in collaboration with all partner countries and training for young African scientists on new and emerging modern technologies have enabled scientists from African partner countries to benefit from this approach and therefore reduce their isolation from the international community. Project partners were able to introduce, test and refine the molecular approaches in selected African partner institutions during the timeframe of the project. For the first time, the project has successfully demonstrated that it is possible to hybridise bambara groundnut. The hybridisation technique was successfully transferred through training courses to all partner countries. The development of an operational method of crossbreeding, with the successful productivity of the first hybrids of bambara groundnut, is a significant achievement because it has opened up the possibility of breeding the first true varieties of this crop. This also provides an opportunity to position QTL (Quantitative Trait Loci) for physiological traits related to resource capture and use. We are now at a critical stage for the future of bambara groundnut. Researchers in the EU INCO-DC funded institutions and elsewhere have significant new knowledge with which to assist farmers in how best to grow the crop. We have the basis for a major bambara groundnut breeding programme to produce novel varieties that best suit the demands of growers and consumers. There is enormous scope for further genetic, physiological and agronomic studies. However, perhaps the most important priority now is to establish promotional and marketing strategies that highlight the nutritional and economic potential of bambara groundnut as a basis to expanding demand for the crop. 3

4 SUMMARY This section summarises key outputs from the multidisciplinary study with the overall aims of increasing the productivity of bambara groundnut (Vigna subterranea (L.) Verdc.) for sustainable food production in semi-arid Africa. Collaborating institutions were Botswana College of Agriculture (BCA), Botswana; the University of Nottingham (UNOTT), UK; the Ministry of Agriculture, Water and Rural Development (MAWRD), Namibia; Technical University of Munich (TUM), Germany and the University of Swaziland (UNISWA), Swaziland. Survey of growers and consumers Indigenous knowledge and information from local farmers and consumers on their preferences for an ideal bambara groundnut type was collated to guide the planning of a breeding programme for the crop. A total of 462 farmers and 115 consumers were interviewed in a series of surveys in Botswana, Namibia and Swaziland between 2001 and The preferences for a bambara groundnut ideotype were found to be common among the three African countries, and included: high yield, large pods, large seeds, spreading growth habit, early maturity and short cooking time. The high yield trait was ranked above all other traits, followed by large pods. From a yield component analysis it was concluded that the achievable objectives for any bambara groundnut improvement programme in these countries should include development of varieties which, within the constraints set by local climate, achieved high biomass production, high harvest index, large pods (1.69 cm diameter and above) and early maturity (3 to 4 months). Agronomic and genetic characterisation of landraces The performance of bambara groundnut landraces was mostly affected by environmental factors, particularly amount and distribution of rainfall. The three seasons were characterised by low, erratic and poorly distributed below average rainfall especially in Botswana and Namibia. Drought tolerance and early maturity should be some of the traits to be incorporated into an ideotype especially for Botswana and Namibia. The best yields ( kg ha -1 ) were obtained in Swaziland where the average total rainfall ranged from 633 mm to 728 mm during the three seasons. The lowest yields were in Botswana ( kg ha -1 ) where the rainfall ranged from 389 mm to 433 mm. Three landraces of bambara groundnut were grown in glasshouses at UNOTT under two moisture regimes (fully irrigated and droughted) to investigate their growth response to soil moisture. The three landraces were DipC from Botswana, S19-3 from Namibia and Uniswa red from Swaziland. The drought treatment was imposed at 42 days after sowing (DAS), beyond which no irrigation was applied. Shoot and root growth was monitored between 21 and 140 DAS. Soil moisture had an effect on the growth of both the shoot and the root. Drought reduced leaf area, dry matter accumulation, seed weight and yield. Drought also significantly (p<0.05) reduced root length density, total root surface area, root diameter and root volume. Landrace variations were found in all the root-related parameters, except for surface area and root volume at 84 DAS. There was preferential allocation of dry matter to the roots with increase in the intensity of drought but this did not occur in Uniswa red. The water use efficiency of the three landraces was found to be 2.1 g m -2 mm -1, a value that is comparable to that of other legumes. Genetic variations in the 4

5 response to drought seem to exist, thereby offering an opportunity for crop improvement based on the existing genetic variation. Landrace S19-3 in particular tended to show signs of exhibiting drought avoidance through a shortened life cycle. UNOTT has developed a non-destructive method of estimating leaf area in bambara groundnut for use in the field in Africa where most laboratories lack access to leaf-area meters. Molecular analysis of germplasm Investigations on the genetic diversity of bambara groundnut (Vigna subterranea) were conducted on 223 accessions from Botswana, Namibia and Swaziland using enzyme system EcoRI/MseI amplified fragment length polymorphism (AFLP) and the simple sequence repeat (SSR) marker techniques. In the AFLP approach, profiles were generated with 10 primer combinations namely: E32M47, E32M49, E33M49, E35M48, E38M53, E39M47, E40M47, E41M58, E44M49, and E46M49. The number of amplified fragments ranged from 55 to 186, with an average of 86. The level of polymorphism was 22%, while polymorphic fragments ranged from nine to 26 with an average of Due to the non-availability of SSR primers specific for bambara groundnut, amplification was done using 14 heterologous primer pairs that are specific for other legume species. The primers used were for soybean (Glycine max), cowpea (Vigna unguiculata), mungbean (Vigna radiata) and common bean (Phaseolus vulgaris). PCR products were obtained with 10 primer pairs, with only one primer pair showing polymorphism. Primer pair AG81 from soybean revealed 18 different alleles at a size range of 136bp to 194bp. A dendrogram resulting from cluster analysis showed that the 223 landraces consisted of three to eight major different genotypes. Furthermore, accessions from neighbouring countries were clustered together but no pure clusters composed of accessions from a single country were observed. The analysis for intra-diversity showed that a landrace consists of three to eight very similar, but different genotypes, for example: AHM genotypes Gap C 4 genotypes AHM genotypes Nyakeni C1 5 genotypes AS 17 3 genotypes Nyakeni C2 8 genotypes Dip C 6 genotypes Uniswa red 3 genotypes OM1 3 genotypes Cibadak 7 genotypes Molecular technology transfer A clear description of the RAPD methodology was published in the Proceedings of a Mid-Project Workshop held in Swaziland in August In country implementation of the protocols at BCA, UNISWA and UNAM (University of Namibia) has been successful. The standardised protocol established at the UNOTT were tested and optimised to suit BCA and UNISWA laboratories. Experiences in different laboratories in relation to RAPD technology and with various thermocyclers are being collated as part of an evaluation programme. Microsatellite (SSR) analyses and the primer sequences that produce polymorphisms have been determined, in-country implementation of this marker system will be effected to compliment RAPD markers. Agro-ecological modelling A simulation model has been developed to predict dry matter production and yield of bambara groundnut in contrasting environments. In this model, crop yields are considered as (a) potential (i.e. limited only by temperature, solar radiation, photoperiod, CO 2 level and landrace characteristics), and (b) water- 5

6 limited (i.e. as for (a), but with the influence of water availability included). The model is sink-limited, this means that the number of pods produced by the plant determines its final yield. The parameters of the model have been determined with experiments in the field, glasshouses and laboratories. The model is a stand-alone computer program written in Delphi 6. It uses climate data, landrace specific parameters, soil data, and physiological relationships running on a daily timestep to determine the biomass production and yield of a landrace in a specific environment. The model will be used to define breeding objectives and provide accurate predictions of performance of a certain landrace in a specific environment. Cross breeding The potential of pure line selection breeding in self-pollinated crops, such as bambara groundnut is limited by the available genetic variability between and within landraces. In any bambara groundnut improvement programme aimed at developing improved cultivars with desirable traits, artificial hybridisation is essential. Cross breeding of selected parental lines allows for the controlled combination of traits, which were previously distributed between the parents, in one new stable line. Additionally, new genetic variability may be produced, possibly resulting in traits previously unknown in the parental lines. Prior to the BAMFOOD research project no success had been achieved in efforts to improve bambara groundnut through cross breeding. As part of the activities of the BAMFOOD research project we have successfully performed a number of crosses, thus demonstrating that it is possible to hybridise bambara groundnut. Success in artificial hybridisation in bambara groundnut depends on a number of factors, including a clear understanding of the floral biology, adoption of an appropriate hybridisation protocol, and careful environmental control during and after pollination. The hybridisation technique was successfully transferred via training courses to Swaziland and Namibia and was performed based on documentation in Botswana. Morphological and molecular markers were used to verify hybrid status of the F 1 and F 2 plants. The development of an operational method of crossbreeding, with the successful productivity of the first hybrids of bambara groundnut, is a significant achievement because it has opened up the possibility of breeding the first improved varieties of this crop. This has also provides an opportunity to position QTL (Quantitative Trait Loci) for novel physiological traits related to resource capture and use. Pure lines were also developed by single seeds descent method. Basic selection methods were transferred to local farmers to help them improve the germplasm available locally. 6