A limiting factor in addressing stalk lodging (breakage of plant stems prior to harvest) is the lack of a reliable method for phenotyping stalk strength. Previous methods of phenotyping stalk strength induce failure patterns different from those observed in natural lodging events. We have designed, fabricated, and tested a new device for field-based phenotyping of stalk strength called "DARLING" (Device for Assessing Resistance to Lodging IN Grains).
Data was gathered on 47 hybrids, grown in 98 distinct environments, spanning four years and 41 unique geographical locations in North America. Using a Bayesian mixed effect model, we show stalk lodging incidence was significantly correlated with DARLING measurements. Based on a joint analysis, we found that stalk bending strength is the most reliable predictor of naturally occurring stalk lodging incidence in maize, followed by rind puncture resistance and cellulose content. The DARLING apparatus induces the characteristic "crease" or Brazier buckling failure patterns observed in naturally lodged stalks. and in agreement with prior research, flexural stiffness values attained using the DARLING apparatus are strongly correlated with bending strength measurements. Additionally, a paired specimen experimental design was used to determine that the flexural data obtained with DARLING is in agreement with laboratory-based flexural testing results of the same specimens. DARLING was also deployed in the field to assess phenotyping throughput (# of stalks phenotyped per hour). Over approximately 5000 tests, the average testing rate was found to be 210 stalks/hour.
The DARLING apparatus provides a quantitative assessment of stalk strength in a field setting. It induces the same failure patterns observed in natural lodging events. DARLING can also be used to perform non-destructive flexural tests. This new technology has many applications, including breeding, genetic studies on stalk strength, longitudinal studies of stalk flexural stiffness, and risk assessment of lodging propensity.