Lodging resistance in maize: A function of root-shoot interactions

The differences in root and stem structure between lodging resistant (LR) and susceptible (LS) genotypes have yet to be fully understood in maize (Zea mays L.). To clarify these differences, lodging rates and yield of LS genotype XunDan20 (XD20) and LR genotype FuMin985 (FM985) across five locations in China from 2014 to 2018 were investigated. Simultaneously, field experiments including genotypes XD20 and FM985 and two plant densities of 75,000 (D75000) and 105,000 plant ha(-1) (D105000) were specifically performed at two locations in North China Plain in 2018. Stem and root lodging rates of XD20 were significantly higher than that of FM985 mainly because FM985 had a larger root system and a stronger basal stem. Compared to XD20, FM985 had significantly larger values in root crown width, root angle, length (+37.1 %), volume (+25.5 %), and length density (+29.9 %) in 0 10 cm soil. Although FM985 had longer and thinner basal stem internodes, the larger sclerenchyma and more compact distribution of epidermal cells in the rind resulted in greater rind penetration strength in FM985 than in XD20. Results from C-13 and N-15 isotope labelling revealed that the high stem strength and root anchorage strength of FM985 were related to the large assimilate allocations to roots and basal internodes. With increased plant density, XD20 had larger reductions in stem morphological parameters, leading to a smaller stem lodging resistance; FM985 showed larger reductions in root traits but still had a high root lodging resistance at high plant density due to the large root system. LR maize allocates more photosynthetic assimilates to roots and stems and maintains a higher capacity of nutrient absorption, reflecting a function of root-shoot interactions during formation and maintenance of lodging resistance.

Automated summary

In maize, differences in root and stem structure between lodging resistant and susceptible genotypes have not been fully understood. By comparing genotypes XD20 and FM985, it was found that FM985 had larger root system and stronger basal stem, leading to higher lodging resistance. FM985 allocated more assimilates to roots and basal internodes, contributing to its high stem and root anchorage strength.