Unoccupied aerial system enabled functional modeling of maize (Zea mays L.) height reveals dynamic expression of loci associated to temporal growth

Unoccupied aerial systems (UAS) were used to phenotype growth trajectories
of inbred maize populations under field conditions. Three recombinant
inbred line populations were surveyed on a weekly basis collecting RGB
images across two irrigation regimens (irrigated and non-irrigated/rain
fed). Plant height, estimated by the 95th percentile (P95) height from UAS
generated 3D point clouds, exceeded 70% correlation to manual ground truth
measurements and 51% of experimental variance was explained by genetics.
The Weibull sigmoidal function accurately modeled plant growth (R2:
>99%; RMSE: < 4 cm) from P95 genetic means. The mean
asymptote was strongly correlated (r2=0.66-0.77) with terminal plant
height. Maximum absolute growth rates (mm d-1) were weakly correlated to
height and flowering time. The average inflection point ranged from 57 to
60 days after sowing (DAS) and was correlated with flowering time
(r2=0.45-0.68). Functional growth parameters (asymptote, inflection point,
growth rate) alone identified 34 genetic loci, each explaining 3 to 15% of
total genetic variation. Plant height was estimated at one-day intervals
to 85 DAS, identifying 58 unique temporal quantitative trait loci (QTL)
locations. Genomic hotspots on chromosome 1 and 3 indicated chromosomal
regions associated with functional growth trajectories influencing
flowering time, growth rate, and terminal growth. Temporal QTL
demonstrated unique dynamic expression patterns not observable previously,
no QTL were significantly expressed throughout the entire growing season.
UAS technologies improved phenotypic selection accuracy and permitted
monitoring traits on a temporal scale previously infeasible using manual
measurements, furthering understanding of crop development and biological
trajectories.