Key-words : crop ideotype, genetic diversity, integrity of plants, intrinsic value, isophenic line mixture varieties, organic plant breeding, organic farming, organic propagation, participatory plant breeding, variety characteristics, seed-borne diseases, seed quality, spring wheat, threshold values, variety concept, variety mixtures.
The organic farming system differs fundamentally from conventional agriculture in the management of soil fertility, weeds, diseases and pests. Organic farmers depend greatly on conventionally bred and produced varieties, but require varieties better adapted to organic farming systems for further optimisation of organic agriculture. This includes a greater need for 'reliable' varieties contributing to higher yield stability.
In this thesis the concept of 'naturalness' as applied in organic agriculture is elaborated and used as guide to develop concepts and strategies for organic plant breeding and propagation. It refers to ecological and ethical principles, including thenon-chemical and agro-ecological approach, but also takes integrity of life into account.
Based on these approaches the organic farming system is described and a general crop ideotype is defined. In the long run organic agriculture can only gain further progress when the genetic basis is renewed and broadened, and when the selection process is conducted under organic farming conditions. For self-fertilisers most promising seems the concept of (isophenic) line mixture varieties, composed of lines being phenotypically uniform but genetically heterogeneous. The ability to produce healthy seed under organic conditions should also be included in the variety ideotype. Further research is needed to develop protocols for seed health testing, to assess threshold values for seed-borne diseases and to design organic seed treatments.
To improve the transparency in the discussions on the ethical aspects in organic agriculture concerning the assessment of the suitability of the breeding and propagation techniques, the concept of the intrinsic value and integrity of plants has been elaborated and operationalised. Therefore principles are derived from the relevant characteristics of the nature of plants at four different levels: integrity of life, planttypic integrity, genotypic integrity and phenotypic integrity. Techniques at whole plant or crop level are most in line with these principles, respecting the self-reproductive ability and the reproductive barriers. The concept of integrity of plants can also give direction to the perception of the plants in the selection process by the so-called breeder's eye.
The consequences of the ecological and ethical principles for the concepts and strategies for organic plant breeding and propagation are demonstrated for the case of spring wheat in the Netherlands, including the adaptation and application of the protocol for Value for Cultivation and Use (VCU) testing. The participation of organic farmers with their experiential knowledge and farmer's eye was essential in the development of the spring wheat ideotype, but can also contribute to the selection process of new varieties.
The proposed organic crop ideotype and variety concept may benefit not only organic farming systems, but in future also conventional systems moving away from high inputs of nutrients and chemical pesticides.
|Doctor of Philosophy
|16 Dec 2002
|Place of Publication
|Published - 16 Dec 2002
- organic farming
- plant breeding
- seed production
- genetic engineering
- triticum aestivum