Heat Shock Proteins and Antioxidant Genes Involved in Heat Combined with Drought Stress Responses in Perennial Rye Grass.

The frequent occurrence of heat and drought stress can severely reduce agricultural production of field crops. In comparison to a single stress, the combination of both heat (H) and drought (D) further reduce plant growth, survival and yield. This study aimed to explore the transcriptional responses of heat shock protein (HSP) and antioxidant genes under H combined D stress in perennial rye grass (PRG). The results demonstrated that oxidative stress indicators (hydrogen peroxide, lipid peroxidation) significantly increased, particularly in the case of combined H and D treatment, suggesting that oxidative stress-induced damage occurred in plants under the combined stresses. Transcriptional responses of heat shock protein 70 (HSP70), heat shock protein 90-6 (HSP90-6), and the mitochondrial small heat shock protein HSP26.2 (HSP26.2) occurred rapidly, and showed high level of expression particularly under H and D stress. Antioxidant genes including ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT), copper-zinc superoxide dismutase (Cu/ZnSOD), peroxidase (POD), ferredoxin-thioredoxin (FTR), thioredoxin (Trx), 2-cysteine peroxiredoxin (2-Cys Prx) showed response to combined H and D, followed by either D or H stress alone in rye grass. An interactome map revealed the close partnership of these heat shock protein genes and antioxidant genes, respectively. These candidate genes were predominantly linked to stress responses and antioxidant defense in plants. These findings may advance our understanding about the HSP and the antioxidant genes underlying combined abiotic stress response and tolerance in perennial rye grass.

Nitric Oxide Prevents Fe Deficiency-Induced Photosynthetic Disturbance, and Oxidative Stress in Alfalfa by Regulating Fe Acquisition and Antioxidant Defense.

Iron (Fe) deficiency impairs photosynthetic efficiency, plant growth and biomass yield. This study aimed to reveal the role of nitric oxide (NO) in restoring Fe-homeostasis and oxidative status in Fe-deficient alfalfa. In alfalfa, a shortage of Fe negatively affected the efficiency of root andshoot length, leaf greenness, maximum quantum yield PSII (Fv/Fm), Fe, S, and Zn accumulation, as well as an increase in H2O2 accumulation. In contrast, in the presence of sodium nitroprusside (SNP), a NO donor, these negative effects of Fe deficiency were largely reversed. In response to the SNP, the expression of Fe transporters (IRT1, NRAMP1) and S transporter (SULTR1;2) genes increased in alfalfa. Additionally, the detection of NO generation using fluorescence microscope revealed that SNP treatment increased the level of NO signal, indicating that NO may act as regulatory signal in response to SNP in plants. Interestingly, the increase of antioxidant genes and their related enzymes (Fe-SOD, APX) in response to SNP treatment suggests that Fe-SOD and APX are key contributors to reducing ROS (H2O2) accumulation and oxidative stress in alfalfa. Furthermore, the elevation of Ascorbate-glutathione (AsA-GSH) pathway-related genes (GR and MDAR) Fe-deficiency with SNP implies that the presence of NO relates to enhanced antioxidant defense against Fe-deficiency stress.

Glutathione Restores Hg-Induced Morpho-Physiological Retardations by Inducing Phytochelatin and Oxidative Defense in Alfalfa.

Mercury (Hg) is toxic to plants, but the effect of glutathione in Hg alleviation was never studied in alfalfa, an important forage crop. In this study, Hg toxicity showed morphological retardation, chlorophyll reduction, and PSII inefficiency, which was restored due to GSH supplementation in alfalfa plants treated with Hg. Results showed a significant increase of Hg, but Fe and S concentrations substantially decreased in root and shoot accompanied by the downregulation of Fe (MsIRT1) and S (MsSultr1;2 and MsSultr1;3) transporters in roots of Hg-toxic alfalfa. However, GSH caused a significant decrease of Hg in the shoot, while the root Hg level substantially increased, accompanied by the restoration of Fe and S status, relative to Hg-stressed alfalfa. The subcellular analysis showed a substantial deposition of Hg in the root cell wall accompanied by the increased GSH and PC and the upregulation of MsPCS1 and MsGSH1 genes in roots. It suggests the involvement of GSH in triggering PC accumulation, causing excess Hg bound to the cell wall of the root, thereby reducing Hg translocation in alfalfa. Bioinformatics analysis showed that the MsPCS1 protein demonstrated one common conserved motif linked to the phytochelatin synthase domain (CL0125) with MtPCS1 and AtMCS1 homologs. These in silico analysis further confirmed the detoxification role of MsPCS1 induced by GSH in Hg-toxic alfalfa. Additionally, GSH induces GSH and GR activity to counteract oxidative injuries provoked by Hg-induced H2O2 and lipid peroxidation. These findings may provide valuable knowledge to popularize GSH-derived fertilizer or to develop Hg-free alfalfa or other forage plants.

Increasing forage yield and effective weed control of corn-soybean mixed forage for livestock through using by different herbicides.

The aim of this study was to evaluate different herbicides for optimum growth, yield and nutritive value of corn-soybean mixed forage under randomized complete block design. The experimental site was selected and divided equally into 3 blocks. Each block was further divided into 5 plots that each plot had 15 square meter space (3 × 5). Five herbicidal treatments were randomly applied over 5 plots and herbicides were used under 5 herbicidal treatments, viz. 1) No herbicide (control); 2) Pendimethalin; 3) Linuron; 4) S-metolachlor and 5) Ethalfluralin. The collected data were analyzed using ANOVA through SAS 9.1.3 software. The results indicated that growth characteristics were not influenced (p > 0.05) by any herbicide. However, arithmetically corn stalk height was highest in the field of Pendimethalin treatment, whereas highest soybean height was found in the field of S-metolachlor. Arithmetically dry matter (DM) yield was increased with herbicidal treatments as compared to that of control treatment. Relatively highest DM yield (130%) was recorded in the treatment of Ethalfluralin followed by Pendimethalin (126%), S-metolachlor (126%) and Linuron (108%) as compared to that of control treatment. The weed emergence was significantly reduced in all herbicidal treatments as compared to that of control (p > 0.05), but the difference among herbicidal treatments was non-significant. It was concluded that weed emergence can be effectively controlled by use of any tested herbicide. However, optimum DM yield can be achieved through using herbicides; Ethalfluralin, Pendimethalin and S-metolachlor.

Evaluating different interrow distance between corn and soybean for optimum growth, production and nutritive value of intercropped forages.

BACKGROUND: Maize fodder is being used as staple feed for livestock but it lacks protein and essential amino acids; lysine and tryptophan. Intercropping maize with leguminous soybean crop is promising technique under limited land resources of South Korea but it can only give considerable advantages when adequate distance is provided between corn and soybean rows. Main aim of present study was to find-out adequate distance between corn and soybean seeding rows for optimum growth, yield and nutritive value of intercropped forage. METHODS: Different interrow distances between corn and soybean were evaluated under four treatments, viz. 1) Corn sole as positive control treatment 2) Zero cm between corn and soybean (control); 2) Five cm between corn and soybean; 3) 10 cm between corn and soybean, with three replicates under randomized block design. RESULTS: Findings depicted that height and number of corn stalks and ears were similar (P > 0.05) among different treatments. Numerically average corn ear height was decreased at zero cm distance. Dry matter percentage in all components; corn stalk, corn ear and soybean was also found not different (P > 0.05) but dry matter yield in component of corn ear was lower (P < 0.05) at zero cm distance as compared to that of 5 and 10 cm interrow distances. In case of nutritive value, total digestible nutrient yield in intercropped corn was also found lower (P < 0.05) at zero cm distance than that of 5 and 10 cm interrow distances between corn and soybean seeding rows. Substantial decrease in dry matter yield of maize ear at zero cm distance might be attributed to factor of closed interrow spacing which made interplant competition more intensified for light interception, necessary for photosynthetic activity. Lower dry matter yield in ear also reduced total digestible nutrients in intercropped maize because it was determining factor in calculation of digestible nutrients. The optimum yield and nutritive value of forage at wider interrow distance i.e. 5 cm between corn and soybean might be due to adequate interseed distance. CONCLUSION: Conclusively, pattern of corn and soybean seeding in rows at 5 cm distance was found suitable which provided adequate interrow distance to maintain enough mutual cooperation and decreased competition between both species for optimum production performance and nutritive value of intercropped forage.