Morphological and mechanical variables associated with lodging in maize (Zea mays L.)

Abstract

Lodging is a function of many factors, but their relative importance is unclear in maize. To clarify this, a two year field experiment that involved six maize genotypes and two plant densities was conducted in 2018 and 2019. Genotypes with a similar growth cycle length but different lodging resistance were selected and sown in April 2018 and May 2019, respectively. As using single indicator aboveground or belowground to assess lodging resistance is inaccurate, both root (R) and shoot (S) traits were considered in the present study. Based on the ratio of root angle and fresh weight of shoot, lodging resistant (LR) genotypes were classified into LRR>S and LRR≈S, and lodging susceptible (LS) genotypes into LSR<S and LSR<<S. LRR>S displayed the largest stem and root safety factor values (SFs and SFr, representing lodging resistance) due to higher dry weight per unit length (DWUL) of the 3rd stem internode aboveground, larger root system, and stiffer upper roots compared to other genotype groups. Both LSR<S and LSR<<S were sensitive to lodging due to large values in fresh weight (FW) of aboveground plant, plant height (PH), and height at center of gravity (GH). At high plant density, LR genotypes had higher SFr and SFs due to reduced FW and self-weight moments of stem (Ms) and root (Mr) compared to LS genotypes. Both SFs and SFr were higher at harvest than at 30 d after silking because of reduced FW and GH and increased DWUL. SFr and SFs were significantly correlated at 30 d after silking and harvest. No lodging occurred at root dry weight> 17.79 g, and SFs had the largest value at DWUL > 0.556 g cm−1. LR genotypes on average yielded better than LS genotypes. There appears to be trade-offs between lodging resistance and high-yielding in maize. Optimizing assimilates partitioning among ear, basal stem, and upper roots should be considered when increasing lodging resistance and yield in maize.