Morpho-physiological profiling of rice (Oryza sativa) genotypes at germination stage with contrasting tolerance to salinity stress

Seed priming with cold plasma, iron, and manganese nanoparticles modulates salinity stress in hemp (Cannabis sativa L.) by improving germination, growth, and biochemical attributes

Using cutting-edge technologies such as non-thermal plasma and metallic nanoparticles has shown promise in ameliorating salinity-induced stress in plants. However, there are still knowledge gaps concerning the most effective strategies for mitigating salinity stress in hemp (Cannabis sativa L.) plants. Consequently, this study was undertaken to investigate the impact of seed priming with cold plasma (CP), iron (Fe), and manganese (Mn) nanoparticles (NPs) on salinity modulation in hemp plants, aiming to improve seed germination, plant growth, and biochemical attributes. A pot experiment was conducted with salinity at three levels (0, 60, and 120 mM NaCl) and seed priming at five levels (control, 60 s CP, 90 s CP, 50 mg L-1 Fe NPs, and 50 mg L-1 Mn NPs). The results showed that salinity at 120 mM decreased germination percentage (GP, 34%), germination speed (GS, 61%), seedling vigor index (SVI, 47%), shoot weight (38%), root weight (15%), chlorophyll (Chl) a + b (31%), and relative water content (RWC, 24%) while increasing malondialdehyde (MDA, 48%) and proline (39%). Seed priming with CP, Fe NPs, and Mn NPs increased plant weight, GP, GS, SVI, RWC, and Chl but decreased MDA accumulation. Fe NPs and salinity at 60 mM led to high levels of total phenolic content and total flavonoid content, which represent 29 and 44% increases, respectively, compared to the control. The heat map showed that among the treatments, GS and SVI had the highest degrees of variability. Fe NPs at 50 mg L-1 and CP at 90 s produced the best plant tolerance to salt stress.

Sugar delivery at the tomato root and root galls after Meloidogyne incognita infestation

Root-knot nematodes (RKNs) infect host plants and obtain nutrients such as sugars for their own development. Therefore, inhibiting the nutrient supply to RKNs may be an effective method for alleviating root-knot nematode disease. At present, the pathway by which sucrose is unloaded from the phloem cells to giant cells (GCs) in root galls and which genes related to sugar metabolism and transport play key roles in this process are unclear. In this study, we found that sugars could be unloaded into GCs only from neighboring phloem cells through the apoplastic pathway. With the development of galls, the contents of sucrose, fructose and glucose in the galls and adjacent tissue increased gradually. SUT1, SUT2, SWEET7a, STP10, SUS3 and SPS1 may provide sugar sources for GCs, while STP1, STP2 and STP12 may transport more sugar to phloem parenchyma cells. At the early stage of Meloidogyne incognita infestation, the sucrose content in tomato roots and leaves increased, while the glucose and fructose contents decreased. SWEET7a, SPS1, INV-INH1, INV-INH2, SUS1 and SUS3 likely play key roles in root sugar delivery. These results elucidated the pathway of sugar unloading in tomato galls and provided an important theoretical reference for eliminating the sugar source of RKNs and preventing root-knot nematode disease.

Genotype-specific germination behavior induced by sustainable priming techniques in response to water deprivation stress in rice

Water stress brought about by climate change is among the major global concerns threatening food security. Rice is an important staple food which requires high water resources. Being a semi-aquatic plant, rice is particularly susceptible to drought. The aim of this work was to develop techniques directed to promote rice resilience to water deprivation stress during germination by implementing specific seed priming treatments. Five popular Italian rice varieties were subjected to priming treatments using novel, sustainable solutions, like poly-gamma-glutamic acid (γ-PGA), denatured γ-PGA (dPGA), and iron (Fe) pulsing, alone or in combination. The effect of the developed priming methods was tested under optimal conditions as well as under water deprivation stress imposed by polyethylene glycol (PEG) treatments. The priming efficacy was phenotypically determined in terms of germination behavior by measuring a series of parameters (germinability, germination index, mean germination time, seed vigor index, root and shoot length, germination stress tolerance index). Biochemical analyses were carried out to measure the levels of iron uptake and accumulation of reactive oxygen species (ROS). Integrative data analyses revealed that the rice varieties exhibited a strong genotype- and treatment-specific germination behavior. PEG strongly inhibited germination while most of the priming treatments were able to rescue it in all varieties tested except for Unico, which can be defined as highly stress sensitive. Molecular events (DNA repair, antioxidant response, iron homeostasis) associated with the transition from seed to seedling were monitored in terms of changes in gene expression profiles in two varieties sensitive to water deprivation stress with different responses to priming. The investigated genes appeared to be differentially expressed in a genotype-, priming treatment-, stress- and stage-dependent manner. The proposed seed priming treatments can be envisioned as sustainable and versatile agricultural practices that could help in addressing the impact of climate challenges on the agri-food system.