Value of genetically heterogeneous crops for organic farming according to DIVERSILIENCE results, and implications for organic breeders and farmers

Summary in the original language of the document

Genetically heterogeneous cultivars of inbred crops may include populations and static or dynamic mixtures of lines or cultivars. Evolutionary populations evolve in target environments under natural selection and possibly under additional mass selection. All of this material can be marketed for European organic systems since 2022. The actual advantage of genetically heterogeneous cultivars over pure line material has not been thoroughly studied. DIVERSILIENCE aimed to provide a scientific assessment of the value of (a) evolutionary populations for wheat and white lupin, (b) composite populations of common bean and runner bean, and (c) cultivar mixtures of wheat and soybean. Besides, it aimed to produce scientific information that could contribute to optimize the development of heterogeneous material. The project results provided direct or indirect evidence for the high agronomic value of populations and cultivar mixtures in terms of yielding ability in low-input systems, yield stability, stress tolerance and/or farmers’ acceptability. Direct evidence arose from the following results:
(a)
in Norway, wheat populations displayed similar grain yield and protein content and higher yield stability relative to pure line varieties;
(b)
in Romania, a six-component wheat cultivar mixture was the only material combining moderate tolerance to a set of abiotic or biotic stresses and good yielding ability;
(c)
in Italy, two white lupin populations showed grain yield, protein content and farmers’ appreciation comparable with those of a pure line variety and an elite breeding line;
(d)
in Romania, a four-component cultivar mixture of soybean displayed higher grain yield than any pure line cultivar, along with no grain quality disadvantage.
Indirect evidence arose from the following results:
(a)
in Denmark, an increase of wheat tolerance to common bunt displayed by mixtures composed of lines with up to six different resistance genes;
(b)
in Slovenia, the high allelic variation for functional markers associated with several agronomically important traits that showed, in particular, by a common bean composite population.
In the case of evolutionary populations, it is noteworthy that this material achieved similar or higher agronomic value than elite pure line cultivars in spite of its much smaller selection cost.
Results of methodological interest for the development of heterogeneous cultivars were:
(a)
the somewhat greater interest of kernel weight than spike appearance for mass selection of wheat populations;
(b)
the limited additional value of farmers’ selection relative to natural selection alone, for white lupin evolutionary populations;
(c)
the agronomic value of genetically broader cultivar mixtures, such as a 6-component mixture for wheat and a 4-component mixture for soybean.
On the whole, the results by the project DIVERSILIENCE justify a greater emphasis on the breeding and the cultivation of genetically heterogeneous cultivars of inbred crops.