Accelerated leaf appearance and flowering in maize after four decades of commercial breeding

Authors: DOS SANTOS, CAIO - Iowa State University; MIGUEZ, FERNANDO - Iowa State University; KING, KYLE - Iowa State University; RUIZ, ALEJO - Iowa State University; SCIARRESI, CINTIA - Iowa State University; BAUM, MITCHEL - Iowa State University; DANALATOS, GERASIMOS J - Iowa State University; STALLMAN, MICKALA - Iowa State University; WILEY, EMILY - Iowa State University; OLMEDO PICO, LIA - Purdue University; THIES, AUGUST - Donald Danforth Plant Science Center; PUNTEL, LAILA - University Of Nebraska; TOPP, CHRISTOPHER - Donald Danforth Plant Science Center; TRIFUNOVIC, SLOBODAN - Bayer Cropscience; EUDY, DOUGLAS - Bayer Cropscience; MENSAH, CLARICE - Bayer Cropscience; Edwards, Jode; SCHNABLE, PATRICK - Iowa State University; LAMKEY, KENDALL - Iowa State University; VYN, TONY - Purdue University; ARCHONTOULIS, SOTIRIOS - Iowa State University

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/7/2023
Publication Date: 7/12/2023
Citation: dos Santos, C.L., Miguez, F.E., King, K.A., Ruiz, A., Sciarresi, C., Baum, M.E., Danalatos, G.N., Stallman, M., Wiley, E., Olmedo Pico, L., Thies, A., Puntel, L.A., Topp, C.N., Trifunovic, S., Eudy, D., Mensah, C., Edwards, J.W., Schnable, P.S., Lamkey, K.R., Vyn, T.J., Archontoulis, S.V. 2023. Accelerated leaf appearance and flowering in maize after four decades of commercial breeding. Crop Science. 1-13. https://doi.org/10.1002/csc2.21044.
DOI: https://doi.org/10.1002/csc2.21044

Interpretive Summary: Maize breeding has resulted in large increases in grain yield in modern hybrids compared to older hybrids, but less is known about how long-term breeding has impacted other plant traits. The present study demonstrated that in the Bayer Crop Science program, breeding has increased the rate of vegetative development so that new leaves appear sooner in modern hybrids. The study also showed that the reproductive phase of development began sooner and even overlapped the vegetative phase such that anthesis and silking began before leaves were fully developed. This study will benefit breeders and producers who need to make decisions based on crop growth rate and stage of development.

Technical Abstract: Maize breeding programs have indirectly altered many plant traits, however, our knowledge of some important phenological traits remains unexplored. One such trait is leaf appearance rate (LAR), which is crucial for predicting maize development. We studied 40 short-season (103-day) and 40 long-season (111-day) hybrids released from 1980 to 2020 by Bayer Crop Science. Measurements included weekly counting of collared leaves across 13 experiments in the US Corn Belt. The progression of leaf numbers was expressed as a function of thermal time and described with a tri-linear model. Results indicated that new 111-day hybrids produce leaves faster than old hybrids throughout the vegetative phase (7.4 and 3.1% faster before and after the 9th leaf stage, respectively), while new 103-day hybrids produce leaves faster only after the 9th leaf stage (9.4%). Thermal time to silking and anthesis decreased by about 1 and 0.56°C-day year-1, respectively. Our data revealed that silking and anthesis can precede the final collared leaf by 96°C-day (3.3 days under optimal conditions), which indicates an overlap between vegetative and reproductive phases. We concluded that maize breeding has indirectly altered the rate of vegetative development of maize hybrids without affecting the final leaf number. Present results expand our knowledge base on the genotypic variability in maize development traits, which can improve empirical and process-based models used for crop stage and yield prediction.