DIVERSILIENCE - Diversifying organic crop production to increase resilience

Crop diversity is indispensable for food security, sustainable development, resilience and adaptation to climate change. Relevant levels of diversity are: (i) diversity of cultivated species in a given region, (ii) diversity of species grown simultaneously (intercropping), (iii) within-species genetic diversity for traits exploitable by plant breeding (e.g. tolerance to specific stresses), and (iv) within-species diversity of cultivated material. Legume crops have key importance for organic systems due to their provision of N and high-protein food or feedstuff.

Such advantages may occur in crop rotations and in intercropping of legume-based species mixtures. Intercropping is known to provide many advantages in terms of agronomic performance and ecosystem services by greater spatial and temporal efficiency of resource use, facilitation effects and limitation of weeds, pests and diseases.

However, its adoption is limited by possible technical challenges in crop sowing or harvesting and crop use that ought to be solved by participatory research with stakeholders, and possible difficulties in obtaining balanced mixtures mostly due to poor competitive ability of legume species. Information on useful plant traits that favour the compatibility of associated species is very limited for grain legumes, especially warm-season ones, while multi-species mixtures have been much less explored than binary mixtures.

Plants of inbred crop varieties and hybrids are genetically uniform. Variety mixtures have displayed positive diversity effects, particularly for disease control. Evolutionary, composite cross populations, which may be developed by natural selection alone or combined with mass selection, are alternative heterogeneous material whose regulation for organic farming is being defined.

However, the potential advantage of heterogeneous material over genetically homogeneous one is poorly documented, with some investigations performed mainly on cereals, particularly wheat. Common bunt, which is the main threat to wheat seed production in organic systems, may represent a key target for disease control by heterogeneous material.

The changing European climate is leading to greater incidence of drought and extreme events, including cold spells on poorly hardened autumn-sown plants (which may induce high legume plant mortality even in Mediterranean sites. It also offers some opportunities, especially in Nordic regions, that require changes in crop types for exploitation. Crop improvement work will take account of this scenario with regard to targeted species and traits, and will rely on farmer participatory selection (which proved highly valuable also for countries with developed agriculture) and innovative marker-based tools (e.g. genomic selection, which proved valuable for legume drought tolerance).

• (i) exploit species genetic diversity to improve crop resilience and adaptation to organic farming, by generating novel selected germplasm and innovative selection tools;
  
• (ii) produce novel evolutionary populations and variety mixtures and assessing their agronomic value relative to genetically homogeneous crops, and optimizing methods for developing heterogeneous material;
  
• (iii) design innovative binary and multispecies intercrops of grain and forage crops in a farmer-participatory manner, and assessing their agronomic value relative to pure stand crops.