conventional release systems are often poorly adapted to small-scale farmer conditions and environments. Similarly, they have not always met the farmers' requirements for multipurpose uses (e.g., fodder and seed), or have not had acceptable postharvest characteristics (e.g., easy to thresh/ process, good taste, good storability). Participatory crop development allows for the better identification of farmer preferences and the requirements of their systems of production as well as optimizing local adaptation through the capture of Genotype X Environment interactions. Genetic diversity can also benefit from participatory approaches as farmers usually select and introduce cultivars that are unrelated to the modern varieties already grown (Witcombe et al., 2001). Other benefits of the participatory approach include a shortened breeding cycle in which new varieties are grown by farmers prior to the 12-15 year period of formal multilocational testing and release. This considerably increases the cost-benefit ratios, net present value and net social benefit (Pandey and Rajatasereekul, 1999). Another benefit of participatory breeding is enhanced compatibility with local or informal seed systems, which is especially important in times of extreme climatic and other stresses. Participatory approaches in livestock research have responded to criticisms that technologies were developed but seldom delivered, or if delivered, did not benefit poor farmers/ herders (Hefferman et al., 2005) and have demonstrated the importance of understanding the particular needs and circumstances of resource poor farmers, building on local knowledge. These approaches have been more appropriate to farmer circumstances and are more likely to be adopted (Catley et al., 2001; Conroy, 2005); however, the benefits for crop and livestock sectors are largely experienced at local or regional levels, and the problem of scaling-up remains.

Participatory approaches have been successfully developed for the domestication of indigenous trees for integration into agroforestry systems.

Throughout the tropics local tree species provide traditional foods and medicines (Abbiw, 1990; Villachica, 1996; Leakey, 1999a; Walter and Sam, 1999; Elevitch, 2006) many of which are marketed locally (Shackleton et al., 2007). Some of these species are being domesticated using a participatory approach to cultivar production (Leakey et al., 2003; Tchoundjeu et al., 2006), using simple and appropriate vegetative propagation methods (Leakey et al., 1990) so that local communities are empowered to create their own opportunities to enter the cash economy (Leakey et al., 2005a) (see 3.2.1.2.1 and 3.2.2.1.6). The use of participatory approaches ensures that the benefits of domestication accrue to the farmers. In this respect, these techniques are in accordance with the Convention on Biological Diversity (Articles 8 and 15) and provide a politically and socially acceptable form of biodiscovery. It is clear that this approach is also encouraging the rapid adoption of both the techniques and the improved cultivars (Tchoundjeu et al., 2006).

Participatory approaches are important in addressing knowledge-intensive, complex natural resource management problems.

In an impact assessment of participatory approaches to development of cassava based cropping systems in Vietnam and Thailand (Dalton et al., 2005), participating farmers gained additional yield benefits, compared with those who merely adopted the new planting material. The integration of management practices into the participatory learning activities resulted in a better understanding of the interrelationships between system components and led to efficiency gains.

Community entry and participatory approaches have higher initial costs, but improved efficiency in technology development, capacity strengthening and learning.

Crop management research increasingly involves farmers in the participatory evaluation of new technologies, identifying adoption constraints and opportunities for improving farm performance to produce more sustainable impact. Between 1999 and 2001, ICRISAT and its partners in Malawi and Zimbabwe evaluated the impact of participatory research in connection with a range of "best bet" soil fertility and water management technologies. The main findings were that community entry and participatory approaches that engage farmers in decision making throughout the research-development- diffusion-innovation process improved efficiency and impact, both through the development of relevant technology and in building farmers' capacity for experimentation and collective learning, but that these benefits had higher initial costs than traditional approaches (Rusike et al., 2006, 2007). The study recommended that public and NGO investments be targeted to build wider-scale district and village-level innovation clusters to make the projects more sustainable over a larger area. Similarly, in Colombia, participatory approaches with local agricultural research committees showed significant social and human capital benefits for members (http://www.prgaprogram.org/index. php?module=htmlpages&func=display&pid=12). However, in Honduras, where educational levels were lower and poverty higher, it was found that the process took longer; because of the need for more intensive assisted learning and social development to support the participatory technology component (Humphries et al., 2000).

3.2.3.3.2 Indigenous knowledge and innovation systems

The complex and dynamic interactions between culture, society and nature and its resources are central to social and environmental sustainability.