Kernel weight contribution to yield genetic gain of maize: a global review and US case studies

Era studies are important to understand historical changes in maize (Zea mays) germplasm and estimate genetic gains, yet information for short‐season maize hybrids is limited. Here, we determine grain yield genetic gain in Bayer short‐season hybrids (100–105 days) and investigate indirect changes made on 17 secondary traits, including yield components (kernel number, weight, and shelling efficiency), and grain quality traits (oil, protein, starch, ethanol, moisture, and test weight). We evaluated 40 maize hybrids released from 1980 to 2020 across 18 environments in the US Corn Belt. Plant density and N‐fertilizer were held constant within each environment. Results indicated a linear increase in grain yield (from 11.1 to 15.3 Mg ha−1, 105 kg ha−1 year−1, or 0.8% year−1) with no sign of a plateau. The increase in grain yield was attributed more to increased kernels per m2 (0.57% year−1) than kernel weight (0.23% year−1). Grain protein concentration decreased until the late 2000s and plateaued thereafter, while starch and ethanol concentration increased until the early 2000s and plateaued thereafter. However, the total amount of protein, starch, and ethanol increased linearly from 1980 to 2020. We concluded that maize breeding for increased grain yield has indirectly affected many traits at different rates and directions. Our results are encouraging for future progress in grain yield increase, update genetic gain information to 2020 for short‐season hybrids, and can inform plant breeders, crop physiologists, agronomists, and crop modelers.

Section: Grain Yield and Componentssupporting

confidence: 89%

Genetic gains in short‐season corn hybrids: Grain yield, yield components, and grain quality traits

King,

Ferela,

Vyn

et al. 2024

“…Lower grain yields of modern hybrids were observed with extremely vertical leaves (>75°), which can be associated with reduced light interception (Duncan, 1971). Leaf angle is one of the many secondary traits that maize breeding has altered over the years (Curin et al., 2020; Duvick et al., 2004; dos Santos et al., 2023; Fernández et al., 2022; Troyer, 1999). While we found no strong association between leaf angle and crop yields, we believe that other traits beyond leaf angle have played a larger role in historical grain yield increases (e.g., radiation use efficiency, Messina et al., 2022; N use efficiency, Mueller et al., 2019; water use efficiency, Reyes et al., 2015; harvest index, Ruiz et al., 2023; staygreen, Duvick et al., 2004; anthesis‐silking interval, dos Santos et al., 2023; grain growth rate and extended grain fill period, Gambin et al., 2023) and that the slowing down of the leaf angle genetic gain is of little concern for future grain yield gains.…”

Section: Discussionmentioning

confidence: 99%

Maize leaf angle genetic gain is slowing down in the last decades

Elli,

Edwards,

et al. 2023

Quantifying historical changes in maize leaf angle and factors affecting it can enhance our understanding of canopy architecture and light capture, and hence crop productivity. Our objectives were to (i) quantify leaf angle genetic gain per canopy position in Bayer's legacy maize (Zea mays L.) hybrids; (ii) dissect the contribution of breeding from plant density on historical changes in leaf angle, and (iii) synthesize our findings with literature to determine leaf angle changes over a century of breeding. We measured leaf angle in 78 maize hybrids released between 1980 and 2020 across eight environments in the US Corn Belt. We found that new hybrids had on average 6° more erect leaves than old hybrids. The leaf angle genetic gain (towards more erect leaves) was on average 0.08% year−1 for the middle canopy leaves and 8‐fold larger for the flag leaf. Our results revealed a synergistic effect with similar contributions of maize breeding and plant density on historical leaf angle changes in the middle canopy. However, changes in the bottom and top canopy leaves were due to breeding. Our results combined with literature revealed consistent trends towards more vertical leaves over a century of maize breeding, but the leaf angle genetic gain is slowing down in the last decades. This suggests that leaf angle may have reached near‐optimum levels and that multiple ways to maintain the grain yield genetic gain have been functioning in maize breeding. Our study provides prospects to inform breeders and crop modelers to better understand maize leaf architecture and crop yields.This article is protected by copyright. All rights reserved

“…The increase in corn and soybean yield was associated with an increase in seeds area −1 (for simplicities sake, "seed" will be used to refer to both the soybean seed and the corn caryopsis) (de Bruin & Pederson, 2009;He et al, 2022;Jin et al, 2010;Echarte et al, 2000;Luque et al, 2006;Russell, 1991;Tollenaar et al, 1992;Voldberg et al, 1997). The contribution of seed size was limited in corn (Barker et al, 2005;de Bruin et al, 2017;Fernandez et al, 2022;He et al, 2022;Russell, 1991;). Chen et al (2016), however, reported a significant contribution when the increase in yield was associated with a longer seed filling period.…”

Section: Crop Sciencementioning

confidence: 99%

Yield improvement and yield components: A comparison of corn and soybean

Egli

2023

Understanding how crop plants changed to accommodate historical yield improvement contributes to a fuller understanding of the response of the crop to management practices. Data sets of yield and plant population from field experiments for corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) were compiled from the literature to evaluate changes in yield and yield components. Most of the data came from management studies and, when there were differences among treatments, the highest‐yielding treatment was used. Yield plant−1 was calculated from yield and plant population. The data sets included both irrigated and non‐irrigated experiments with a total of 231 observations (1906 to 2019) for corn and 172 (1919 to 2018) for soybean. The yield data did not segregate by irrigation treatment, so the data were pooled for analyses. The yield increased linearly for both species (10.4 g m−2 d−1 for corn and 2.6 g m−2 d−1 for soybean). Plant population increased steadily for corn (fivefold) while there was no significant change for soybean. The consistent yield increase coupled with different population trends resulted in completely different trends in yield plant−1. Yield plant−1 increased in soybean while there was no change in corn. The soybean plant had the flexibility to accommodate the more than twofold increase in yield plant−1. The corn plant is potentially flexible, but the flexibility did not play a major role in hybrid improvement, so it was necessary to increase the population to accommodate higher yields.