Proceedings of the Second International Workshop on Striga Ouagadougou, Upper Volta 5-8 October 1981 Sponsored by the International Development Research Centre (IDRC) and the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) ICRISAT International Crops Research Institute for the Semi-Arid Tropics ICRISAT Patancheru P.O. Andhra Pradesh, India 502 324 1983 Workshop Coordinators and Scientific Editors K.V. Ramaiah and M.J. Vasudeva Rao Publication Editor Vrinda Kumble Acknowledgments The organizers acknowledge with appreciation the assistance of the International Development Research Centre (IDRC), Canada, for financial support in organizing this workshop and bringing out the proceedings, and the Ministry of External Affairs and Ministry of Higher Education and Scientific Research, Government of Upper Volta, for their permission to hold the workshop. The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) is a nonprofit scientific educational institute receiving support from donors through the Consultative Group on International Agricultural Research. Donors to ICRISAT include governments and agencies of Australia, Belgium, Canada, Federal Republic of Germany, France, India, Italy, Japan, Mexico, the Netherlands, New Zealand, Nigeria, Norway, Sweden, Switzerland, United Kingdom, United States, and the following international and private organizations: Asian Development Bank, European Economic Community, Ford Foundation, International Bank for Reconstruction and Development, International Development Research Centre, International Fertilizer Development Center, International Fund for Agricultural Devel• opment, Leverhulme Trust, Organization of Petroleum Exporting Countries, Rockefeller Foundation, and the United Nations Development Programme. Responsibility for the information in this publication rests with ICRISAT or the individual authors. Where trade names are used this does not constitute endorse- ment of or discrimination against any product by the Institute. Correct citation: ICRISAT (International Crops Research Institute for the Semi-Arid Tropics). 1983. Proceedings of the Second International Workshop on Striga, 5-8 Oct 1981, IDRC/ICRISAT, Ouagadou- gou, Upper Volta. Patancheru, A.P., India: ICRISAT. Contents F o r e w o r d J.C. Davies V O p e n i n g Session 1 Introduction D.J.Andrews 3 Objectives of the Workshop K.V. Ramaiah 4 Discours d'ouverture Djigma Albert 5 Welcome Djigma Albert 5 Session 1 —Setting the S c e n e 7 Striga—Analysis of Past Research and Summary C. Parker 9 of the Problem Session 2 — T a x o n o m y a n d M o r p h o l o g y 17 Biosystematic Research in the Genus L.J. Musselman Striga (Scrophulariaceae) and C. Parker 19 Les especes de Striga en Haute-Volta H. Reneaud 25 Striga Species in Upper Volta (English Translation) H. Reneaud 27 Session 3—Germination and Host-Parasite Specificity 29 Factors Influencing Striga Seed Germination and Host-Parasite Specificity C. Parker 31 Inhibition of Germination in Striga by Means C. Pesch, of Urea (Abstract) A.H. Pieterse, and W.A. Stoop 37 Evidence of Enzyme Activities in the Haustorium of Striga gesnerioides (Scrophulariaceae) A.T. Ba 39 Effect of Stimulant plus Herbicide on R.S. Norris Striga Germination and R.E. Eplee 43 Striga Resistance Screening of Some Cultivars of Pearl Millet, Sorghum, Maize, and Cowpea A T . Ba 47 Session 4—Control Methods 51 Striga Research at ICRISAT, Upper Volta Center K.V. Ramaiah 53 Breeding Sorghum with Resistance to Striga asiatica M.J. Vasudeva Rao, at ICRISAT Center V.L Chidley, K.V. Ramaiah, and L.R. House 61 Criblage des cultivars de petit mil pour la Z.G. Roger resistance au Striga hermonthica et K.V. Ramaiah 77 Screening of Pearl Millet Cultivars for Resistance Z.G. Roger and to Striga hermonthica (English Translation) K.V. Ramaiah 83 Striga Studies and Control in Nigeria A.T. Obilana 87 Progress in Control of Striga asiatica in the USA R.E. Eplee 99 Occurrence of Striga and Its Possible Control W.A. Stoop, in Cropping Systems in Northern Ghana H. Lanting, and K.V. Ramaiah 103 The Need for Consideration of Biocontrol in Striga L.J. Musselman 109 Studies on the Root Parasite, Striga asiatica Bharathalakshmi 111 Session 5 — S u m m a r i e s of Discussions 115 Laboratory and Pot-Screening Techniques 117 Field-Screening Techniques 117 Breeding Programs 118 Agronomic Practices 118 S o m m a i r e des discussions 119 Procedures de criblage en laboratoire et en vase 119 Techniques de criblage au champ 120 Programme d'amelioration 120 Pratiques agronomiques 120 Session 6 — P l e n a r y Session a n d R e c o m m e n d a t i o n s 123 A p p e n d i x 1 — P a r t i c i p a n t s 127 Foreword More than 1800 phanerogamic parasites have been recorded throughout the world. Among the most important are the parasitic figworts or Scrophulariaceae, which are economically damaging root parasites. The genus Striga, with more than 50 spe• cies, belongs to this family; however, only a few are completely parasitic and damaging to their hosts. Undoubtedly, the major species are S. hermonthica—a widespread and important pest of cereals in Africa—and S, asiatica, an important pest both in Asia and in eastern and southern Africa. Although precise estimates of crop loss are difficult to make and data are incomplete, it is well known that severe losses, amounting in many seasons to total crop failure, are caused by these parasitic weeds. However, there is still a general lack of awareness of the magnitude and importance of the problem. These Proceed• ings bring together the results of discussions held at Ouagadougou, Upper Volta, in October 1981, where the latest research findings and proposals for further research were presented. They highlight the important advances made in knowledge of the pest species, methods of control, and techniques for breeding for resistance to these noxious weeds. It is hoped that this publication will prompt increased effort to be focused on methods of combating Striga and reducing the serious losses it causes to cereal production, and on strengthening links between scientists working in numerous programs to produce solutions to outstanding research problems. J.C. Davies Director International Cooperation* *Presently Deputy Chief Natural Resources Adviser (Research), Overseas Development Administration, UK. O p e n i n g Session Chairman: K.V. Ramaiah Rapporteur: Z.G. Roger Introduction D. J. Andrews* The International Crops Research Institute for the Strict quarantine regulations on the movement of Semi-Arid Tropics (ICRISAT) has a mandate for Striga from one place to another compel research in improving and stabilizing the grain yields of the area where the problem exists. Because of the sorghum, millet, pigeonpea, chickpea, and ground• severity of the Striga problem in Africa, ICRISAT nut in the semi-arid tropical (SAT) regions of the decided to shift the main work to the African world. Considerable progress has been made at continent. ICRISAT Center in developing high-yielding cultiv- Thanks to the timely financial support from the ars of these crops, particularly sorghum and millet. International Development Research Centre Unfortunately, their introduction into the Sahelian (IDRC) and to the ready agreement of the Govern• countries is limited by problems that are specific to ment of Upper Volta to the proposal, we began our the region. Stabilization of grain yields in this region Striga work at Kamboinse Agricultural Experimental may be achieved by building up resistance to var• Station in 1979. ious yield reducers, such as drought, insect pests, This program in Upper Volta was for 3 years, to diseases, and the root parasites, Striga spp. the end of 1981. During this phase, attempts were Striga is a serious problem of the African conti• made to understand the problem and to explore nent, although it exists in a less severe form in various possibilities of controlling the parasite, with southeast Asia and the United States of America. the major emphasis on developing host-plant ICRISAT recognized this problem in 1974, soon resistance. after the establishment of the Institute in 1972 in This workshop during the final year of the project India, and started work on developing resistant cul- provided a timely opportunity to review our work tivars of sorghum. The results of international with Striga specialists from other parts of the world Striga-resistant sorghum trials conducted in Africa to determine what should be done in the future. in 1977 indicated large differences in virulence Research efforts should be oriented to finding between Indian Striga (Striga asiatica) and African simpler, cheaper, and easier solutions that are soci• Striga (S. hermonthica). It was also realized that ologically acceptable to subsistence farmers in development of cultivars resistant to S. hermon­ Africa. thica cannot be accomplished by working in India. *Millet Improvement Program, ICRISAT, Patancheru, A.P., India. 3 Objectives of the Workshop K.V. Ramaiah* The first International Striga and Orobanche Work- 4. To discuss the possibilities of basic investiga- shop was held in Khartoum, Sudan, in 1978. The tions on mechanisms of resistance; i.e., factors present workshop is limited to Striga only, to allow that influence Striga seed germination, etc., for more discussion. During the last 3 years consid- which may lead to new control strategies. erable interest has been created in the Striga prob- 5. To consider resistant cultivars and the prob- lem, and several national and international lems involved in developing new stable resist- institutions have started working on it. As a result, ant cultivars in particular. This discussion many data, both basic and applied, have accumu- should include laboratory and field-screening lated. There are also several basic problems that techniques, selection criteria, and breeding are not clearly understood and need further strategies.