Ultimate success in exploiting the genetic capabilities of plants to grow in nutrient-stressed environments of the semi-arid tropics (SAT) requires a holistic view of food systems to ensure that genetic selections for improved yields on nutrient-poor soils will actually be adopted by farmers. This book sets out to address the important issue of how physiological mechanisms of nutrient uptake can best be combined with genetic options to improve the adaptation of crops to low-nutrient availability, thereby enhancing productivity of nutrient poor soils in the semi-arid tropics. The book examines (i) the sustainability of breeding for low-nutrient environments from the viewpoint of three interrelated disciplines; physiology, breeding, and socio-economics, (ii) candidate mechanisms and physiological traits to enhance uptake and utilization efficiencies, (iii) genetic approaches for manipulation of crop plants to enhance root exudation and access nutrients in the rhizosphere, and (iv) field practices and farmers' preferences for crop varieties grown in low-nutrient environments. Finally, the role of modelling in improving nutrient efficiency in cropping systems, recommendations for future research needs and strategies were highlighted. Attended by 50 international participants, this book is the outcome of the workshop held at ICRISAT-India during 27-30 September 1999 to mark the culmination of the Government of Japan/ICRISAT Project.

Inhalt

1. Welcome address.- 2. Government of Japan Project activities at 1CRISAT 1984-1999.- 3. Physiological traits for crop yield improvement in low N and P environments.- 4. Prospects for using conventional techniques and molecular biological tools to enhance performance of 'orphan' crop plants on soils low in available phosphorus.- 5. Ex-ante impact assessment and economic analysis of breeding for nutrient efficiency and alternate strategies, a conceptual model and research issues: A socio-economist's view.- 6. Breeding for low-nutrient environments: Is it sustainable?.- 7. Breeding for low-nutrient environments.- 8. Genetic adaptation of crop plants to low-nutrient environments: morphological and ecophysiological characteristics of adaptation.- 9. Genotypic variability and physiological characteristics of crop plants adapted to low-nutrient environments.- 10. Physiological adaptations for nitrogen use efficiency in sorghum.- 11. Photosynthesized carbon translocation and distribution of crops adapted to low-nutrient environments.- 12. Varietal differences in root growth as related to nitrogen uptake by sorghum plants in low-nitrogen environment.- 13. Genotypic variability in phosphorus solubilizing activity of root exudates by pigeonpea grown in low-nutrient environments.- 14. Root cell-wall properties are proposed to contribute to phosphorus (P) mobilization by groundnut and pigeonpea.- 15. Role of soil microorganisms in improving P nutrition of plants.- 16. Phosphorus use efficiency as related to sources of P fertilizers, rainfall, soil, crop management, and genotypes in the West African semi-arid tropics.- 17. Modelling root-induced solubilization of nutrients.- 18. Scope for genetic manipulation of mineral acquisition in chickpea.- 19. Aluminum tolerance in nodulated N2-fixing legumes species native to two contrasting savanna sites.- 20. Effect of rock phosphate and superphosphate fertilizer on the productivity of maize var. Bisma.- 21. Candidate mechanisms.- 22. Assessing germplasm collections for traits useful in plant nutrition.- 23. Root exudates as mediators of mineral acquisition in low-nutrient environments.- 24. Genetic control of root exudation.- 25. Transporter genes to enhance nutrient uptake: Opportunities and challenges.- 26. The phosphate uptake mechanism.- 27. Breeding for better symbiosis.- 28. Genetic approaches for manipulating crop plants to enhance root exudation and access low nutrients in the rhizosphere.- 29. Breeding crops for enhanced micronutrient content.- 30. Appropriate farm management practices for alleviating N and P deficiencies in low-nutrient soils of the tropics.- 31. Farmer preferences and legume intensification for low nutrient environments.- 32. Nutrient balances: A guide to improving the sorghum- and groundnut-based dryland cropping systems in semi-arid tropical India.- 33. Preplant moisture and fertility conditions as indicators of high and stable yields in rainfed cropping systems.- 34. Role of modelling in improving nutrient efficiency in cropping systems.- 35. Combining genetic improvement with natural resource management.- 36. Closing remarks.- 37. Future research needs, priorities, and strategies.- 38. Participants.