Organic plant breeding and propagation: concepts and strategies

Summary

The organic farming system differs fundamentally from conventionally 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 a guide to develop concepts and strategies for organic plant breeding and propagation.It refers to ecological and ethical principles,including the non-chemical and agro-ecological approach,and also taking the 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 the concept of (isophenic)line mixture varieties seems most promising,being composed of lines which are 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 transparency in the discussions on the ethical aspects of 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 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.