No abstract

Drought is a devastating environmental constraint affecting the agronomic production of barley. To facilitate the breeding process, abundant germplasm resources and reliable evaluation systems to identify the true drought-tolerant barley genotypes are needed. In this study, 237 cultivated and 190 wild barley genotypes, originating from 28 countries, were screened for drought tolerance under the conditions of both water deficit and polyethylene glycol (PEG)-simulated drought at seedling stage. Drought stress significantly reduced the plant growth of all barley genotypes, but no significant difference in drought-induced reduction in the performance of barley seedlings was observed under these two drought conditions. Both cultivated and wild barley subspecies displayed considerable genotypic variability in drought tolerance, which underpinned the identification of 18 genotypes contrasting in drought tolerance. A comparative analysis of drought effects on biomass, water relation, photosynthesis, and osmotic adjustment was undertaken using these contrasting barley genotypes, in order to verify the reliability of the screening and to obtain the credible traits as screening criteria of drought tolerance in barley. As expected, the selected drought-tolerant genotypes showed much less reduction in shoot biomass than drought-sensitive ones under water deficit, which was significantly positively correlated with the results of large-scale screening, confirming the reliability of the screening for drought tolerance under two drought conditions in this study. Likewise, the traits of water relation, photosynthetic activity, and osmotic adjustment differed greatly between the contrasting genotypes under water deficit stress, and they were highly correlated to the growth of barley seedlings, suggesting the potential of them to be the selection criteria for drought tolerance. The analysis of the variable importance of these traits in drought tolerance indicated that sap osmolality and relative water content in the youngest fully-expanded leaf are the suitable selection criteria of screening for drought tolerance in barley at seedling stage.

No abstract

The use of nanofabricated materials is being explored for the potential in crop disease management. Chemically synthesized micronutrient nanoparticles (NPs) have been shown to reduce crop diseases; however, the potential of biogenic manganese NPs (bio‐MnNPs) in disease control is unknown. Here, the potential and mechanism of bio‐MnNPs in suppression of watermelon Fusarium wilt, caused by Fusarium oxysporum f. sp. niveum (Fon) are reported. Bio‐MnNPs are synthesized by cell‐free cultural filtrate of a waterrmelon rhizosphere bacterial strain Bacillus megaterium NOM14, and are found spherical in shape with a size range of 27.0–65.7 nm. Application of bio‐MnNPs at 100 µg mL−1 increases Mn content in watermelon roots/shoots and improves growth performance through enhancing multiple physiological processes, including antioxidative capacity. Bio‐MnNPs at 100 µg mL−1 suppress Fusarium wilt through inhibiting colonization and invasive growth of Fon in watermelon roots/stems, and inhibit Fon vegetative growth, conidiation, conidial morphology, and cellular integrity. Bio‐MnNPs potentiate watermelon systemic acquired resistance by triggering the salicylic acid signaling upon Fon infection, and reshape the soil microbial community by improving fungal diversity. These findings demonstrate that bio‐MnNPs suppress watermelon Fusarium wilt by multiple ex planta and in planta mechanisms, and offer a promising nano‐enabled strategy for the sustainable management of crop diseases.

Chromium (Cr) is a serious environmental contaminant that drastically limited the crop yields. Nitric oxide (NO) and spermine (Spm) portrayal significance in improving the plant tolerance against abiotic stresses. Therefore, we investigate the protective efficacy of seed priming with NO (100 μM) and/or Spm (0.01 mM) in minimising the Cr-induced toxic effects in rice (Oryza sativa L.) plants. Our outcomes revealed that Cr alone treatments (100 μM) notably reduced the seed germination rate, plant growth, photosynthetic apparatus, nutrients uptake and antioxidant defence system, but extra generation of reactive oxygen species (ROS). Interestingly, the combine applications of NO and Spm significantly reversed the Cr-induced toxic effects by reducing the Cr-accumulation, maintaining the nutrient balance, improving the germination indices, levels of photosynthetic pigments (chl a by 24.6%, chl b by 36.3%, chl (a + b) by 57.2% and carotenoids by 79.4%), PSII, photosynthesis gas exchange parameters and total soluble sugar (74.9%) by improving antioxidative enzyme activities. As a result, NO + Spm lowered the accumulation of oxidative markers (H2O2 by 93.9/70.4%, O2˙− by 86.3/69.9% and MDA by 97.2/73.7% in leaves/roots), electrolyte leakage (71.4% in leaves) and improved the plant growth traits. Based on these findings, it can be concluded that NO triggers Spm to minimise the Cr-accumulation and its adverse effects on rice plants. Additionally, combined treatments (NO + Spm) were more effective in minimising the Cr-induced toxic effects in comparison to NO and Spm alone treatments. Thus, co-exposure of NO and Spm may be utilised to boost rice tolerance under Cr stress conditions.