Proposed Changes of Gene Flow and Institutional Relationship

Wild relatives and landraces still account for the bulk of genetic diversity within a crop genepool. Formal breeding reaggregates existing genetic variation from these two sources. While new techniques employed in mutation breeding programs and some engineered genes (e.g., those with enhanced herbicide resistance) may actually introduce new variations, isozyme and molecular data on the amounts of diversity in wild relatives, landraces and modern cultivars indicate that wild relatives and landraces remain the main sources of genetic diversity in crop genepools.13 Conserving these sources is therefore crucial to the future of crops. Our existing system of genetic resource conservation and use, however, may need to be redirected in order to maintain this diversity.

The current unidirectional flow of genetic resources into formal centralized breeding of elite varieties with high yields and specific resistance offers little that is useful to small scale farmers who are engaged in maximizing genetic diversity and who maintain landraces. For poorer farmers on marginal lands, a growing

Fig. 11.1. Maintenance and use of genetic diversity: existing system.

Fig. 11.1. Maintenance and use of genetic diversity: existing system.

reliance on high yielding varieties of improved crops reduces their options for coping with variable environmental conditions and exploiting niches and micro-environments in their farming systems.

New varieties of crops able to meet the challenge of marginal areas must come from the use of the genetic resources conserved from these areas. We need to conserve not only the genes themselves but also the farming systems and agroecosystems that produce and maintain genetic diversity. This requires strong positive feedback in the germplasm improvement and conservation system directed to traditional farming systems which use and maintain landraces. Those inputs need to be in a form that farmers can use as part of their own system with its particular practices of selection, breeding and management of crops. In this way they can continue to use and develop genetic diversity in crops as an integral part of their own social and economic development.14

Many genebanks are finding that their holdings are increasingly dominated by advanced cultivars, with landraces poorly rep resented and inadequately documented.15 In the final analysis, we may be losing significant portions of the crop genepool by not feeding back into the sources of genetic variation in crops, namely, farmers and their interactions with complex environmental pressures. In Africa and India, for example, "cassava (Manihot esculenta) yields increased up to 18 times after genes from wild Brazilian cassava, conferring disease resistance, were incorporated into local varieties."16 Other minor and locally important crops benefit from similar inputs.

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