Evaluation of Root Lodging Resistance During Whole Growth Period in Maize Using the Anti-Lodging Index Defined as Root Failure Moment Divided by Wind Resultant Moment

Root lodging due to strong storm wind is a common problem in maize (Zea mays) production, leading to reduced crop yield and quality and harvest efficiency. Little information is available on quantifying effects of vertical leaf area distribution on root lodging in crops such as maize. The anti-lodging index of root was computed by the formula: ALroot = Mroot / Mwind, where AL denotes anti-lodging index, and M moment of force. Root failure moment of force equals to moment arm times max root side-pulling force measured in situ by means of the digital pole dynamometer, and wind resultant moment of force is estimated with vertical leaf area distribution and wind speed. Two maize cultivars, with contrasting root lodging resistance, were examined at 5 different growth stages from V8 to physiological maturity in 2019 and 2020, in Qingdao, China. Root anti-lodging index in tested cultivars fluctuated to a small extent within any year during whole growth period excluding at V8, while there was an inter-annual shift in index means (1.23 vs 0.84). Both root failure moment and wind resultant moment increased first and then decreased with the growth stage, and their influence on root anti-lodging index varied with the year. At wind grade 6, effect sizes, as contribution to root anti-lodging index, of root moment and wind moment were respectively 0.88 and 0.98. The difference in anti-lodging index between cultivars seemed to be disappearing as wind grade goes up. Root failure moment of force positively related to single root tensile resistance, root-soil ball volume, root number and total root length, whose correlation coefficient was the maximum of 0.94. Root anti-lodging index of maize proved stable from V8 on during whole growth period, and vertical leaf area distribution played a substantial role in maize root lodging in terms of wind resultant moment. Our findings provide the insights into root lodging events in crops such as maize, and would serve an approach to assessing crop root lodging resistance in breeding and cultivation programs.

Wide–Narrow Row Planting Pattern Increases Root Lodging Resistance by Adjusting Root Architecture and Root Physiological Activity in Maize (Zea mays L.) in Northeast China

Root lodging (RL) in maize can reduce yield and grain quality. A wide–narrow row planting pattern can increase maize yield in the growing regions of northeastern China, but whether it can improve RL resistance is not clear. Therefore, in this study, the root architecture distribution, root physiological activity, and root lodging rate under planting pattern 1 (uniform ridge of 65 cm, east–west ridge direction) and pattern 2 (wide–narrow rows, 40 double narrow rows and 90 wide rows, north–south ridge direction) were studied. The results showed that the RL rate under pattern 2 was significantly lower than that under pattern 1. The number and diameter of nodal roots on the upper node, the root failure moment, and the root bleeding sap intensity at the 3 weeks after VT under pattern 2 were significantly higher than those under pattern 1. Root length density in the 0–40 cm soil layer tended to be inter-row distributed. Therefore, the RL resistance of maize under pattern 2 was increased through an adjustment in the root architecture distribution and root physiological activity in northeastern China.

Altering maize (Zea mays) seedlings’ growth and lignification processes by action of novel synthesized compounds

Effective management of the course of crop vegetation and adaptation to biotic and abiotic stresses is a prerequisite for stable grain production and requires replenishment of the arsenal of plant growth regulators. The effect of novel synthesized cage amides on maize seedlings morphogenesis has been tested. Seeds of a mid-early maize hybrid 'DN Galatea' after the pre-sowing treatment with 0.01% solutions of test compounds were grown in distilled water. The roots and shoots sections of 10-day-old maize seedlings were stained with phloroglucinol solution to reveal the lignin-containing anatomical structures. The effects of nine different test compounds, exceeding the well-known effects of the phytohormone auxin, promoted the maize seedlings’ linear growth, increased wet weight of roots and shoots, and dry biomass accumulation both in seedlings roots and shoots. Several test compounds activated the dry weight accumulation process without significantly affecting the root and shoot length. In the maize seedlings’ roots, an increase in the diameter and number of the xylem vessels was found, as well as an increase in the lignin-containing layer thickness of the endoderm cells in the root cortex. In the maize seedlings’ shoots, the test compounds caused an increase in the thickness of the lignin-containing outer layer of the seedlings’ first leaf. In general, the test compounds’ effect on seedling roots can potentially enhance root formation; increase efficiency of the roots water-conducting system and the tissues’ strength, thus reducing the likelihood of root lodging in maize plants. The effects of the test compounds revealed in the seedlings’ shoots reflect the activation of the shoots’ structure formation and may have a positive value for enhancing the strength of the plant stems and counteracting the stem lodging of the maize plants.

Evaluation of root lodging resistance during whole growth period in maize using the anti-lodging index defined as root failure moment divided by wind resultant moment

Background: Root lodging due to strong storm wind is a common problem in maize (Zea mays) production, leading to reduced crop yield and quality and harvest efficiency. Little information is available on quantifying effects of vertical leaf area distribution on root lodging in crops such as maize. The anti-lodging index of root was computed by the formula: ALroot = Mroot / Mwind, where AL denotes anti-lodging index, and M moment of force. Root failure moment of force equals to moment arm times max root side-pulling force measured in situ by means of the digital pole dynamometer, and wind resultant moment of force is estimated with vertical leaf area distribution and wind speed. Two maize cultivars, with contrasting root lodging resistance, were examined at 5 different growth stages from V8 to physiological maturity in 2019 and 2020, in Qingdao, China. Results: Root anti-lodging index in tested cultivars fluctuated to a small extent within any year during whole growth period excluding at V8, while there was an inter-annual shift in index means (1.23 vs 0.84). Both root failure moment and wind resultant moment increased first and then decreased with the growth stage, and their influence on root anti-lodging index varied with the year. At wind grade 6, effect sizes, as contribution to root anti-lodging index, of root moment and wind moment were respectively 0.88 and 0.98. The difference in anti-lodging index between cultivars seemed to be disappearing as wind grade goes up. Root failure moment of force positively related to single root tensile resistance, root-soil ball volume, root number and total root length, whose correlation coefficient was the maximum of 0.94. Conclusion: Root anti-lodging index of maize proved stable from V8 on during whole growth period, and vertical leaf area distribution played a substantial role in maize root lodging in terms of wind resultant moment. Our findings provide the insights into root lodging events in crops such as maize, and would serve an approach to assessing crop root lodging resistance in breeding and cultivation programs.

Brace root phenotypes predict root lodging susceptibility and the contribution to anchorage in maize

A changing global climate brings increasingly prevalent and severe storms that threaten crop production by imparting mechanical stresses. Plant failure due to mechanical stress is termed lodging and in the United States, yield loss due to lodging has been estimated at 7-25% for maize (Zea mays). In maize, the presence of specialized aerial brace roots has been shown to increase anchorage and root lodging resistance. However, beyond scoring for presence, there have been limited attempts to define the brace root phenotypes that optimize anchorage. This study reports variable root lodging and plant biomechanics in a population of 52 maize inbred lines. To quantify the variation in brace root phenotypes within this population, a semi-automated phenotyping workflow was developed. These empirical measurements were integrated into predictive random forest models to demonstrate that brace root phenotypes can classify root lodging incidence and plant biomechanics. The prediction accuracy of these models is driven by multiple brace root phenotypes suggesting that anchorage can be optimized by the manipulation of multiple functional traits. Plant height has been previously associated with lodging susceptibility yet the inclusion of plant height as a predictor does not always improve prediction accuracy. Previously, brace root node number has been shown to be genetically linked to plant height and here we show that additional brace root phenotypes are linked to plant height but with opposing effects on root lodging susceptibility. Together these data define the important brace root phenotypes that predict root lodging resistance and demonstrate the need to uncouple the linkage between plant height and root traits for the development of climate resilient crops.