Genotype Rankings for Nutrient Stress Resistance are Unrelated to Stress Severity in Cultivated Sunflower (Helianthus annuus L.)

Abstract

Abiotic stress limits crop productivity worldwide, making stress‐resistant crops a major goal for improving food security. Stress resistance is often assessed by comparing genotypes under a single control and stressed level of an abiotic factor, then ranking the genotypes’ overall performance, using a metric like geometric mean productivity (GMP). However, abiotic stress is rarely a presence/absence phenomenon, but often varies continuously. Here, we tested whether the common practice of assessing performance using a single control and stress level is predictive of performance across a range of stress levels. Twelve sunflower genotypes were grown in the greenhouse under one of eight nutrient levels (from non‐limiting to severely limiting) and assessed for performance (shoot dry mass at the budding stage) and related traits at both seedling and budding stages. Contrary to expectations, genotype rankings for GMP were consistent regardless of the two nutrient levels used to calculate GMP. This suggests that, for nutrient stress in sunflower, studies using an arbitrary control and stress level are broadly representative: genotypes with high GMP exhibit high GMP regardless of the nutrient levels used. In addition, GMP values were highly correlated with performance in the respective nutrient levels from which they were calculated; thus, higher GMP for a given genotype indicates that it performed well (relative to other genotypes) under both stressed and non‐stressed conditions. Together, these findings strongly support the current paradigm of comparing genotypes at a single control and stress level as a valid strategy for screening for nutrient stress resistance in sunflower. However, few traits were consistently associated with performance (shoot dry mass) at either high‐ or low‐nutrient availability, and seedling traits were rarely predictive of budding‐stage traits and performance, suggesting further studies are needed to determine the mechanisms underlying nutrient stress resistance in this important oilseed crop.

Vigour/tolerance trade‐off in cultivated sunflower (Helianthus annuus) response to salinity stress is linked to leaf elemental composition

“…Twenty inbred genotypes (Table S1), including elite varieties and landraces, of cultivated sunflower (Helianthus annuus L.) were selected from a diversity panel, sunflower association mapping (SAM) population of 288 genotypes (Mandel, Dechaine, Marek, & Burke, 2011;Nambeesan et al, 2015). Genotypes were selected based on their differential responses in previous abiotic stress studies (Bowsher et al, 2017;Masalia, Temme, Torralba, & Burke, 2018). Plants were grown in a split-plot design with four replicates per treatment and genotype at the Plant Biology Greenhouse on the University of Georgia campus located in Athens, GA, from September to October of 2016.…”

Multiple genomic regions influence root morphology and seedling growth in cultivated sunflower (Helianthus annuus L.) under well-watered and water-limited conditions

“…Thus, to protect against a potential methodological artifact in terms of biomass estimation, we did not analyze aboveground or total biomass values any further. Instead, we used stem height and diameter as proxies for overall plant performance; stem diameter in particular is known to be a good predictor of biomass accumulation in sunflower [ 73 ].…”

Plasticity and the role of mass‐scaling in allocation, morphology, and anatomical trait responses to above‐ and belowground resource limitation in cultivated sunflower (Helianthus annuus L.)

“…To add to our understanding of plant responses to resource limitation, we examined trait responses to light and nutrient limitation of traits across different trait categories (biomass allocation, morphology, and anatomy) and organs (leaf, stem, and root) in cultivated sunflower. Prior research has shown strong plastic responses to resource limitation and other environmental factors in H. annuus (Bowsher et al., 2017; Donovan et al., 2014; Masalia et al., 2018; Rico et al., 2013; Temme et al., 2019). Specifically, we sought to answer the following questions: How do mass allocation, organ morphology, and anatomy change with above‐ and belowground resource limitation, and what role does size scaling of traits play in this? How do traits compare for magnitude of plasticity and what role does size scaling of traits play in this? Do traits show a coordinated shift due to resource limitation across all organs and what role does size scaling of traits play in this? …”