Crop lodging, pod fertility and yield formation in canola under varying degrees of short‐term heat stress during flowering

Abstract

There has been little research on crop lodging and yield determination in response to varying degrees of heat stress in canola. This research aimed to examine root morphology, pod fertility, seed yield and crop lodging of two canola genotypes subjected to normal temperature (23/17°C, light/dark, as CK), and three elevated temperature regimes imposed at flowering for a short term (10 days), namely CK+2 (25.0/22.0°C, light/dark), CK+4 (27.0/24.0°C) and CK+6 (29.0/26.0°C), in a controlled growth facility. Elevated temperature treatment, CK+4 and CK+6, displayed a significant adverse effect on seed yield and stem lodging. Compared to the CK, a significant yield loss of 35.6% and 48.7% in CK+4 and CK+6, respectively, was mainly due to poor pod fertility. This was evident from the smaller number of total filled pods (−21% in the CK+4 and −25% in the CK+6), low success ratio of pod developed (−25%, CK+4 and −29%, CK+6) and poor pollen viability (−36%, CK+4 and −50%, CK+6), averaged across both genotypes. Lateral root development was sensitive to the elevated temperature treatment, showing significant reductions in the lateral root morphology (8.0%-28.5%), while the taproot was relatively tolerant to the elevated temperature stress. A strong relationship between root electrical capacitance and lateral root morphology (R 2 > .74**) indicates that electrical measurements could be used as a non-destructive method for evaluating root parameters under elevated temperatures. Higher risk of stem lodging (21.4% lower stem safety factor) compared to the CK was evident under severe elevated temperature stress, as ascribed from the reduced stem bending strength that was caused by the deteriorating stem mechanical properties such as decreased flexural rigidity and weakened vascular bundle size (i.e. stunted fibre cell, and thinned size of fibre wall, deteriorated secondary xylem and smaller secondary phloem). These results were further verified by the principal component analysis and structural equation model. The root lodging risk was not influenced by the elevated temperature regime, primarily due to the unaffected anchorage strength and height of the centre of gravity. This information will be useful in improving lodging resistance and alleviating the related impact of heat stress in canola.

Modelling the impact of cabbage stem flea beetle larval feeding on oilseed rape lodging risk

“…Whilst this indicates that CSFB tunnelling predominantly leads to physiological impacts, there are several biochemical factors that could also be impacted, including lignin biosynthesis, cellulose biosynthesis and silica uptake. 28,[41][42][43] Lignin, cellulose, hemicellulose and chitin are known to impact the elastic modulus, therefore affecting the flexural rigidity of the basal stem. 44,45 Silicon is an important structural component related to stem strength, and the application of silicon could increase the content of lignin in sclerenchyma cells, consequently improving stem strength in OSR crops.…”

“…The results have demonstrated that CSFB tunnelling resulted in a reduction in both stem diameter and stem strength, indicating that lower stem strength may be mainly caused by thinner stems. Whilst this indicates that CSFB tunnelling predominantly leads to physiological impacts, there are several biochemical factors that could also be impacted, including lignin biosynthesis, cellulose biosynthesis and silica uptake 28,41–43 . Lignin, cellulose, hemicellulose and chitin are known to impact the elastic modulus, therefore affecting the flexural rigidity of the basal stem 44,45 .…”

Starch structural and functional properties of waxy maize under different temperature regimes at grain formation stage

“…The gene expression of the starch synthase was downregulated, and the enzymatic activity of amylase was enhanced; their influence was higher under 40 °C than under 32 °C compared with the control ( Kumari et al, 2020 ). With the severity of HS at flowering stage, the grain yield of canola and stem lodging were aggravated due to poor pod fertility and low success ratio of developed pods ( Wu, Duncan, & Ma, 2021 ). In our previous studies, we observed that post-silking day HS enlarged the starch granule size and increased the amylopectin chain-length, which led to the decrease of pasting viscosity and increase of retrogradation, but the influences depended on hybrids ( Lu, Shen, Cai, Yan, Lu, & Shi, 2014 ), durations ( Gu, Huang, Ding, Lu, & Lu, 2018 ), and stages ( Lu, Sun, Yan, Wang, Xu, & Lu, 2013 ).…”