Screening Soybean for Adaptation to Relay Intercropping Systems: Associations between Reproductive Organ Abscission and Yield

Abstract

The flower and pod abscission is one of the characteristics of soybean that severely limits yield, especially when intercropped with maize. Therefore, suitable soybean cultivars for intercropping are urgently needed to improve farmland productivity. We conducted a two-year field experiment to evaluate the flower and pod abscission, dry matter production, and yield advantages of 15 soybean cultivars. The results of the principal component analysis (PCA) and cluster analysis (CA) showed that 15 soybean cultivars were classified into three groups, i.e., high-yielding group (HYG), mid-yielding cultivars (MYG), and low-yielding cultivars (LYG). In the HYG group, ND12 and GX3 had characteristics of more flowers and pods and less abscission of flowers and pods. Moreover, the net assimilation rate (NAR) and relative growth rate (RGR) of HYG were significantly higher than the other. The HYG obtained a considerably higher partition ratio of 53% from biomass to seed than the other. Therefore, selecting and breeding cultivars with the characteristics of more flowers and pods and less abscission of flowers and pods can help to increase soybean yield in intercropping.

Light recovery after maize harvesting promotes soybean flowering in a maize–soybean relay strip intercropping system

“…In addition to the photoperiod, shading plays an essential role in influencing the soybean flowering phenotype by adjusting the GAs and carbohydrate contents. The delayed soybean flower appearance time in IS and MS were consistent with those of previous studies, where shading in intercropping systems inhibited soybean growth, reduced substance accumulation, and delayed soybean flowering (Du et al, 2022). Simultaneously, our experiments revealed that IS not only extended the flowering period of soybeans (Figure 2C,F) but also promoted flower formation at the later flowering stage (A-E).…”

“…For instance, we found that in intercropping patterns, choosing late-maturing and multibranching soybean varieties (ND25) resulted in higher flower and pod counts, which increased the yield of soybeans. Du et al (2022) found that selecting and breeding cultivars with more flowers and pods and less abscission of flowers and pods can help increase soybean yield in intercropping. Wu et al (2022) also found that late-maturing varieties exhibited higher post-flowering substance accumulation and lower yield losses than early maturing varieties.…”

“…typically cultivated in Southwest China, that is, Nandou25 (ND25), Gongqiu8 (GQ8), Guixia7 (GX7), and NanNong966 (NN996), were used as test materials. Each soybean variety was selected based on significant differences in flowering number and maturity time in a previous study (Du et al., 2022). Characteristic data, including growth period, branch number, and pod number for each variety, are shown in Table S1.…”

“…Usually, in intercropping systems, the canopy environment is modified during the growth period, which causes significant differences in light distribution in space and time in different intercropping systems (Pelech et al., 2023). Soybeans in the IS showed a shorter period of flower and pod competition, which contributed to the recovery of soybean flowering (Du et al., 2022). Conversely, shading in MS continues from the first flowering stage (R1) to the beginning of the seed stage (R5), increasing the nutrient competition between flowers and pods (Wang et al., 2020).…”

“…Depending on the co-growth period, intercropping systems can be classified as intercropping and relay-intercropping systems. In the maize-soybean intercropping system (MS), maize and soybean are sown simultaneously, and maize shading mostly appears during the soybean reproductive stage (Fang et al, 2022). In the maize-soybean relay-intercropping system (IS), soybeans are sowed later than maize, and maize shading appears during the soybean vegetative stage (Raza et al, 2019).…”