Nondestructive Phenomic Tools for the Prediction of Heat and Drought Tolerance at Anthesis in Brassica Species

Abstract

<jats:p>Oilseed Brassica species are vulnerable to heat and drought stress, especially in the early reproductive stage. We evaluated plant imaging of whole plant and flower tissue, leaf stomatal conductance, leaf and bud temperature, photochemical reflectance index, quantum yield of photosynthesis, and leaf gas exchange for their suitability to detect tolerance to heat (H) and/or drought (D) stress treatments in 12<jats:italic> Brassica</jats:italic> genotypes (G). A replicated factorial experiment was set up with 7 d of stress treatment from the beginning of anthesis with various levels of three factors<jats:italic> H</jats:italic>,<jats:italic> D</jats:italic>, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:mi>G</mml:mi></mml:mrow></mml:math>. Most phenomics tools detected plant stress as indicated by significant main effects of<jats:italic> H</jats:italic>,<jats:italic> D</jats:italic>, and<jats:italic> H×D</jats:italic>. Whole plant volume was highly correlated with fresh weight changes, suggesting that whole plant imaging may be a useful surrogate for fresh weight in future studies. Vc<jats:italic>max</jats:italic>, the maximum carboxylation rate of photosynthesis, increased rapidly on day 1 in H and H+D treatments, and there were significant interactions of<jats:italic> G×H</jats:italic> and<jats:italic> G×D</jats:italic>. Vc<jats:italic>max</jats:italic> of genotypes on day 1 in H and H+D treatments was positively correlated with their harvested seed yield. Vc<jats:italic>max</jats:italic> on day 1 and day 3 were clustered with seed yield in H and H+D treatments as shown in the heatmaps of genotypic correlations. TPU, the rate of triose phosphate use, also showed significant positive genotypic correlations with seed yield in H+D treatments. Flower volume showed significant interactions of<jats:italic> G×H</jats:italic> and<jats:italic> G×D</jats:italic> on day 7, and flower volume of genotypes on day 7 in H was positively correlated with their harvested seed yield. There were few interactions of<jats:italic> G×H</jats:italic> or<jats:italic> G×D</jats:italic> for leaf stomatal conductance, leaf and bud temperature, photochemical reflectance index, and quantum yield of photosynthesis. Vc<jats:italic>max</jats:italic>, TPU, and volume of flowers are potential nondestructive phenomic traits for heat or combined heat and drought stress tolerance screening in<jats:italic> Brassica</jats:italic> germplasm.</jats:p>

Meta‐analysis of drought and heat stress combination impact on crop yield and yield components

“…Nonetheless, the relative effect of the combined heat and drought stress treatment was consistently more dramatic than the impact of drought or heat applied individually. This finding highlights the importance of studies that specifically address heat and drought stress combination (Mittler 2006, Chen et al 2019, Zandalinas et al 2017, 2020, Mazdiyasni and AghaKouchak 2015, Lobell and Gourdji 2012, Lawas et al 2018b. Importantly, the results presented here underscore the need to focus on stress combinations occurring during the reproductive growth stages, as the impact on yield is more severe than when stress combination occurs during vegetative development (Fig.…”

“…While growing on non‐irrigated lands, these crops are potentially subjected to different environmental stress conditions such as drought, heat stress and their combination. Heat waves combined with acute and prolonged drought stress can have a devastating outcome for agriculture, as well as economic and social stability, primarily impacting drylands used for grain production worldwide (Ciais et al 2005, Mittler 2006, Chen et al 2019, Zandalinas et al 2020). The 2003 drought and heat episode across Europe, for example, caused a 30% reduction in agricultural production (Ciais et al 2005).…”

Rapid temperature responses of photosystem II efficiency forecast genotypic variation in rice vegetative heat tolerance

“…From the A n -c i response measurements, we modelled V cmax and J max to gauge the efficiency of carboxylation by Rubisco and the rate of electron transport, respectively. These parameters are frequently assessed to determine the photo-physiological response to heat stress (Perdomo et al, 2016;Haworth et al, 2018;Thomey et al, 2019;Chen et al, 2019); however, we believe that this is the first instance of genetic variation in these parameters being tested under heat stress in rice in a substantial and genetically diverse set of lines. All accessions demonstrated a downregulation in V cmax (Figure 8a), which is likely to be linked to Rubisco activase thermosensitivity (Feller et al, 1998;Makino and Sage, 2007), as well the degradation of other Calvin-cycle enzymes (Sharkey, 2005) and general metabolic reprogramming in the chloroplasts (Wang et al, 2018).…”

Transient daily heat stress during the early reproductive phase disrupts pod and seed development in Brassica napus L.

“…The mechanism of heat stress sensitivity in oilseed rape was related to disruptions in gametogenesis, pollination, fertilization, and early embryogenesis (Angadi et al., 2000; Chen et al., 2019; Singh et al., 2008) and seed development during the development of pods (siliques) (Morrison, 1993; Weymann et al., 2015; Young et al., 2004). Transient daily heat stress (with temperatures ramping up and down each day from minimum to maximum) for 3 days after first open flower did not reduce leaf stomatal conductance, fresh weight of above‐ground biomass, whole plant volume, and flower volume compared with the control, but significantly decreased seed yield (Chen et al., 2019). Also, heat stress was not associated with a reduction in vegetative growth or photosynthetic activity of Brassica species, and Vcmax , the maximum carboxylation rate of photosynthesis, was double the value in the control treatment during the first 3 days of heat treatment (Chen et al., 2019).…”