Decreased Lodging Resistance in High-Yielding Maize Cultivars Released from the 1980s to the 2010s in China

Abstract

The maize (Zea mays L.) grain yield potential in China saw significant growth between the 1980s and 2010s, largely driven by improvements in optimal planting density. Denser plantings, however, come with an elevated risk of lodging, causing potential yield penalties. This study utilized seven hybrid cultivars representing various eras to assess advancements in maize breeding aimed at researching lodging resistance in optimal planting density. In 2021 and 2022, the hybrids were planted at four densities and assessed during the silking stage for stalk-breaking force, vertical root-pulling resistance (VRPR), plant and internode morphology, basal internode rind penetration strength (RPS), crush strength (CS), bending strength (BS), and shoot fresh matter. Grain yield was measured at full maturity. The average grain yield increase was 190.23 kg ha−1 year−1 or 1.12% with year of release (YOR−1) during the experimental years. However, lodging resistance analysis showed that the stalk-breaking force and the VRPR decreased by 0.64 N year−1 (0.46% YOR−1) and 8.95 N year−1 (0.16% YOR−1), respectively. Furthermore, there was a dramatic decrease in mechanical strength, with RPS, CS, and BS decreasing by 0.21%, 0.31%, and 0.44% YOR−1, respectively. The dry weight, dry weight per unit length, and diameter of the average basal internode also decreased by 0.28%, 0.36%, and 0.16% YOR−1, respectively. Additionally, the ear and gravity ratios decreased by 0.15% and 0.07% YOR−1, respectively. Other lodging resistance traits did not differ significantly from the year of release. Our results indicate that maize breeding efforts during this time led to higher grain yield alongside reduced ear and gravity ratios, with less emphasis placed on lodging resistance. As modern maize improvement efforts strive for high-yield cultivation in dense plantings, it is imperative to also consider lodging resistance traits. This study discusses fundamental maize breeding strategies and provides new insights into the genetic progress of lodging resistance in dense plantings.

Keywords: maize, grain yield potential, Lodging resistance, plant morphology, mechanical strength