HighlightRice exposed to a toxic cadmium concentration recovers from toxicity symptoms after supplementation of the medium with silicon, and transcript levels of marker genes are readjusted to that in unstressed conditions.

Summary Genetic biofortification requires knowledge on natural variation and the underlying mechanisms of micronutrient accumulation. We therefore studied diversity in grain micronutrient concentrations and spatial distribution in barley (Hordeum vulgare), a genetically tractable model cereal and an important crop with widespread cultivation. We assembled a diverse collection of barley cultivars and landraces and analysed grain micronutrient profiles in genebank material and after three independent cultivations. Lines with contrasting grain zinc (Zn) accumulation were selected for in‐depth analysis of micronutrient distribution within the grain by micro‐proton‐induced X‐ray emission (μ‐PIXE). Also, we addressed association with grain cadmium (Cd) accumulation. The analysis of > 120 lines revealed substantial variation, especially in grain Zn concentrations. A large fraction of this variation is due to genetic differences. Grain dissection and μ‐PIXE analysis of contrasting lines showed that differences in grain Zn accumulation apply to all parts of the grain including the endosperm. Cd concentrations exceeded the Codex Alimentarius threshold in most of the representative barley lines after cultivation in a Cd‐contaminated agricultural soil. Two important conclusions for biofortification are: first, high‐Zn grains contain more Zn also in the consumed parts of the grain; and second, higher micronutrient concentrations are strongly associated with higher Cd accumulation.

Combating hidden hunger through molecular breeding of nutritionally enriched crops requires a better understanding of micronutrient accumulation. We studied natural variation in grain micronutrient accumulation in barley (Hordeum vulgare L.) and searched for candidate genes by assessing marker-trait associations (MTAs) and by analyzing transcriptional differences between low and high zinc (Zn) accumulating cultivars during grain filling. A collection of 180 barley lines was grown in three different environments. Our results show a pronounced variation in Zn accumulation, which was under strong genotype influence across different environments. Genome-wide association mapping revealed 13 shared MTAs. Across three environments, the most significantly associated marker was on chromosome 2H at 82.8 cM and in close vicinity to two yellow stripe like (YSL) genes. A subset of two pairs of lines with contrasting Zn accumulation was chosen for detailed analysis. Whole ears and flag leaves were analyzed 15 days after pollination to detect transcriptional differences associated with elevated Zn concentrations in the grain. A putative α-amylase/trypsin inhibitor CMb precursor was decidedly higher expressed in high Zn cultivars in whole ears in all comparisons. Additionally, a gene similar to barley metal tolerance protein 5 (MTP5) was found to be a potential candidate gene.

Breeding and engineering of biofortified crops will benefit from a better understanding of bottlenecks controlling micronutrient loading within the seeds. However, few studies have addressed the changes in micronutrient concentrations, localization, and speciation occurring over time. Therefore, we studied spatial patterns of zinc and iron accumulation during grain development in two barley lines with contrasting grain zinc concentrations. Microparticle-induced-X-ray emission and laser ablation-inductively coupled plasma mass spectrometry were used to determine tissue-specific accumulation of zinc, iron, phosphorus, and sulfur. Differences in zinc accumulation between the lines were most evident in the endosperm and aleurone. A gradual decrease in zinc concentrations from the aleurone to the underlying endosperm was observed, while iron and phosphorus concentrations decreased sharply. Iron co-localized with phosphorus in the aleurone, whereas zinc co-localized with sulfur in the sub-aleurone. We hypothesize that differences in grain zinc are largely explained by the endosperm storage capacity. Engineering attempts should be targeted accordingly.

In light of the continuous increase in organic agriculture, the availability of organic seeds has gained a lot of importance. Especially since the new EU organic regulation came into force on 1 January 2022, proposing reducing the possibility of using untreated conventional seeds in the absence of organic seeds in the future. At the same time, the breeding of tolerant, resistant and adapted varieties is at the basis of organic production as is research to improve seed production and seed quality. In this study, we investigated seed production of 8 tomato genotypes. The aim was to see whether different fruit harvesting frequencies affect seed quality and germination rate. The hypotheses we tested were (i) whether regularly removing fruits from the field would affect total fruit and seed harvest, (ii) whether storage of fruits and (iii) their ripening stage at harvest, had an impact on seed germination. Our results show that while seed production differs between genotypes and extraction time-points, different harvesting procedures, and with that different fruit maturity levels, did not affect thousand-seed weight and seed germination; these findings benefit both small and larger-scale seed producers.