TY - JOUR

T1 - Genotype and cytokinin effects on soybean yield and biological nitrogen fixation across soil temperatures

AU - Kempster, Robert

AU - Barat, Mercedes

AU - Bishop, Laura

AU - Rufino, Mariana

AU - Borras, Lucas

AU - Dodd, Ian

N1 - This is the peer reviewed version of the following article: Kempster, R, Barat, M, Bishop, L, Rufino, M, Borras, L, Dodd, IC. Genotype and cytokinin effects on soybean yield and biological nitrogen fixation across soil temperatures. Ann Appl Biol. 2021; 178: 341– 354. https://doi.org/10.1111/aab.12652 which has been published in final form at https://onlinelibrary.wiley.com/doi/10.1111/aab.12652 This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.

PY - 2021/3/30

Y1 - 2021/3/30

N2 - High nitrogen (N) supply is required for high‐yielding soybean, but low soil temperatures in either early production systems or cool environments delay nodulation and limit biological nitrogen fixation (BNF). Because cytokinins are key signalling hormones in mediating nodule formation and our initial controlled environment experiment indicated that seed cytokinin treatment increased early BNF and total nodule area, it was used in field trials. Cytokinin was applied (seed or foliar) to two commercial soybean genotypes (DM50I17 and DM40R16) in field trials with early (September and early November) and conventional (late November) sowing dates in Argentina. In the field, DMR50I7 achieved consistent yields across sowing dates because increased BNF compensated for limited soil N uptake in early sowing dates, also leading to 25% higher nitrogen use efficiency (NUE). Surprisingly, soil N uptake was more cold‐sensitive than BNF with greater and prolonged N fixation in early sowing, perhaps through delayed nodulation, leading to improved N harvest index. Cytokinin seed treatment increased BNF (26%) in DM40R16 especially in early sowing dates. Although cytokinin improved cold tolerance of BNF, this was not explained by altered nodulation and did not increase yield. Here we show genetic differences in N supply in commercial soybean genotypes and the importance of BNF to maintain yield in early sown soybean.

AB - High nitrogen (N) supply is required for high‐yielding soybean, but low soil temperatures in either early production systems or cool environments delay nodulation and limit biological nitrogen fixation (BNF). Because cytokinins are key signalling hormones in mediating nodule formation and our initial controlled environment experiment indicated that seed cytokinin treatment increased early BNF and total nodule area, it was used in field trials. Cytokinin was applied (seed or foliar) to two commercial soybean genotypes (DM50I17 and DM40R16) in field trials with early (September and early November) and conventional (late November) sowing dates in Argentina. In the field, DMR50I7 achieved consistent yields across sowing dates because increased BNF compensated for limited soil N uptake in early sowing dates, also leading to 25% higher nitrogen use efficiency (NUE). Surprisingly, soil N uptake was more cold‐sensitive than BNF with greater and prolonged N fixation in early sowing, perhaps through delayed nodulation, leading to improved N harvest index. Cytokinin seed treatment increased BNF (26%) in DM40R16 especially in early sowing dates. Although cytokinin improved cold tolerance of BNF, this was not explained by altered nodulation and did not increase yield. Here we show genetic differences in N supply in commercial soybean genotypes and the importance of BNF to maintain yield in early sown soybean.

U2 - 10.1111/aab.12652

DO - 10.1111/aab.12652

M3 - Journal article

VL - 178

SP - 341

EP - 354

JO - Annals of Applied Biology

JF - Annals of Applied Biology

SN - 0003-4746

IS - 2

ER -