Supply Chain Perspectives on Breeding for Legume–Cereal Intercrops

Abstract

Compared to sole crops, intercropping—especially of legumes and cereals—has great potential to improve crop yield and resource use efficiency, and can provide many other ecosystem services. However, the beneficial effects of intercrops are often greatly dependent on the end use as well as the specific species and genotypes being co-cultivated. In addition, intercropping imposes added complexity at different levels of the supply chain. While the need for developing crop genotypes for intercropping has long been recognized, most cultivars on the market are optimized for sole cropping and may not necessarily perform well in intercrops. This paper aims to place breeding targets for intercrop-adapted genotypes in a supply chain perspective. Three case studies of legumes and cereals intercropped for human consumption are used to identify desirable intercrop traits for actors across the supply chains, many of which are not targeted by traditional breeding for sole crops, including certain seed attributes, and some of which do not fit traditional breeding schemes, such as breeding for synchronized maturity and species synergies. Incorporating these traits into intercrop breeding could significantly reduce complexity along the supply chain. It is concluded that the widespread adoption and integration of intercrops will only be successful through the inclusion and collaboration of all supply chain actors, the application of breeding approaches that take into account the complexity of intercrop supply chains, and the implementation of diversification strategies in every process from field to fork.

Intercropped Maize and Cowpea Increased the Land Equivalent Ratio and Enhanced Crop Access to More Nitrogen and Phosphorus Compared to Cultivation as Sole Crops

“…Studies have shown that some legumes, such as white lupine, can develop proteoid roots or cluster roots in soils low in available P. These specialized roots improve P uptake and, through the exudation of organic acids, reduce soil pH, solubilizing P from stable P pools [47,48]. Cowpea, whether grown as a sole crop or intercropped, also appears to have the ability to access more P than other species, increasing the activities of acid and alkaline phosphatases [16,17]. Makoi et al [49] demonstrated that increasing cowpea density significantly enhanced acid and alkaline phosphatase activity, under conditions like those in this study, providing a primary explanation for the result.…”

“…The results showed that the triticale-pea and barley-pea intercrops provided the highest grain yields and average weights of 1000 grains. Maize (Zea mays L.)-legume intercrops can also provide protein-rich food in low-input agricultural systems, bringing overall benefits to soil fertility conservation, pest management, and animal feed [16,17]. In Malawi, a three-year study was carried out to compare the performance of maize-legume intercropping under conservation agriculture and conventional tillage on twelve farms [18].…”

“…The relative contribution of each of the '4C effects' (complementarity, cooperation, compensation, and competition) determines the result and can emphasize the yield advantages of intercropping [21]. The challenge to improve the intercropping consists of optimizing agronomic traits that reduce the negative effect of competition and, at the same time, improve the aspects of complementarity, cooperation, and compensation [17,21]. Estimating the land equivalent ratio (LER) in intercrops also leads to an understanding of the interactions affecting yields.…”

Cereal-legume intercropping: a smart review using topic modelling

“…In addition, intercropping traits involved in technical, quality and other downstream processes including ripening time and seed color require further optimization. Furthermore, also complementary aspects related to species synergy during the growth period, for example, “mixing ability” and “species compatibility” are equally important breeding goals that, to date, have received little attention in scientific literature ( Kiaer et al., 2022 ).…”

Concepts of trait diversity – the key to effective IPM for resilience in arable systems?

“…Alongside this, the trend towards homogeneity has favoured a predominantly reductionist approach to modern crop breeding (e.g. Kiær et al, 2022), which assumes that the desirable traits for enhanced crop performance can be assembled in single, optimised genotypes to meet the goals of crop quantity, uniformity and consistency valued by processors and other end users. While this approach combines much functional diversity from many sources in a cultivar's pedigree and has led to highly productive modern cropping systems, the lack of diversity across scales, from crops to value chains, has created vulnerabilities in food systems that become particularly apparent during periods of external stress (Khoury et al, 2014; Mahaut et al, 2021).…”