Plant Breeding for Intercropping in Temperate Field Crop Systems: A Review

Abstract

Monoculture cropping systems currently dominate temperate agroecosystems. However, intercropping can provide valuable benefits, including greater yield stability, increased total productivity, and resilience in the face of pest and disease outbreaks. Plant breeding efforts in temperate field crops are largely focused on monoculture production, but as intercropping becomes more widespread, there is a need for cultivars adapted to these cropping systems. Cultivar development for intercropping systems requires a systems approach, from the decision to breed for intercropping systems through the final stages of variety testing and release. Design of a breeding scheme should include information about species variation for performance in intercropping, presence of genotype × management interaction, observation of key traits conferring success in intercropping systems, and the specificity of intercropping performance. Together this information can help to identify an optimal selection scheme. Agronomic and ecological knowledge are critical in the design of selection schemes in cropping systems with greater complexity, and interaction with other researchers and key stakeholders inform breeding decisions throughout the process. This review explores the above considerations through three case studies: (1) forage mixtures, (2) perennial groundcover systems (PGC), and (3) soybean-pennycress intercropping. We provide an overview of each cropping system, identify relevant considerations for plant breeding efforts, describe previous breeding focused on the cropping system, examine the extent to which proposed theoretical approaches have been implemented in breeding programs, and identify areas for future development.

Coadaptation of coexisting plants enhances productivity in an agricultural system

“…In the last years, breeding for more diverse crop systems (i.e. mixtures) has gained more attention (Bourke et al, 2021; Haug et al, 2021; Moore et al, 2022) and genes were identified which might be relevant for breeding in more diverse crop systems (Wuest et al, 2022; Wuest and Niklaus, 2018). Furthermore, a recent study found evidence for genetic and epigenetic evolution of monoculture and mixture ecotypes in grassland species (van Moorsel et al, 2019).…”

“…Most of the commonly grown crops nowadays are bred for and multiplied in monocultures where they experience only intraspecific interactions and are thus not necessarily well suited to be grown in mixtures where also interspecific interactions occur. Hence, crop ecotypes specifically bred for mixtures might achieve additional yield benefits (Bourke et al, 2021; Brooker et al, 2021; Chen et al, 2021; Moore et al, 2022). Indeed, ecological studies conducted in grasslands have shown that plants adapt to growth in polycultures, with significant positive effects on community-level productivity (Zuppinger-Dingley et al, 2014) due to less intense competition in mixtures of adapted plants compared to the same mixtures of naïve plants (Schöb et al, 2018) – a result that could be confirmed in an annual crop system (Stefan et al, 2022).…”

Toward plant breeding for multicrop systems

“…Compared with other multicrop systems described so far, intercropping involves more direct interactions among crop species. Therefore, in addition to the breeding goals described above, breeding programs focused on intercropping will select plants to enhance positive interactions (e.g., facilitation, niche differentiation) and reduce negative interactions (e.g., competition) among intercropping partners ( 39 ).…”

The relationship between shifts in the rhizosphere microbial community and root rot disease in a continuous cropping American ginseng system

“…However, how the specific microbial community of perennial crops forms little by little is still not fully understood. Perennial crops have their particularities, and many perennial plants are valuable economic crops, but perennial plants' diseases usually worsen over years of cultivation (Li et al, 2020 ; Moore et al, 2022 ). It is unclear whether the aggravation of plant disease during the development stages was associated with the succession of its rhizosphere microbial community, though.…”