Use of Lentinan and Fluopimomide to Control Cotton Seedling Damping-Off Disease Caused by Rhizoctonia solani

Lentinan (LNT) is a natural and functional polysaccharide isolated from Lentinus edodes fruiting bodies, which functions in stimulating the plant immune response, improving plant disease resistance and regulating plant growth. This study explores the use of LNT as a plant growth regulator and attractant in cotton production. After treatment with LNT, the content of malondialdehyde (MDA) in cotton seeds decreased, whereas the activities of polyphenol oxidase (PPO), superoxide dismutase (SOD) and peroxidase (POD) in leaves increased significantly. LNT also promoted the growth and development of cotton plants and significantly reduced the incidence of cotton damping-off disease. The relative expression of salicylic acid pathway-related genes in cotton also increased significantly. The prevention mechanism of fluopimomide was also evaluated, and the result showed lower EC50 values and was effective in controlling cotton seedling disease caused by Rhizoctonia solani in both greenhouse experiments and field trials. The use of LNT and fluopimomide in controlling cotton seedling damping-off disease showed a synergistic effect in field trials. These results will provide a new insight into the agricultural application of LNT as a biological fungicide in the field of biological controls.

Thanatephorus cucumeris (many names, depending on host).

Introduction: T. cucumeris is a pathogen with a worldwide distribution and in Japan alone T. cucumeris is reported to infect 35 orders, 52 families, 125 genera and 142 species of plant (Ogoshi, 1996). Yield and economic losses caused by T. cucumeris have not been determined in the majority of crops and environments. The most comprehensive estimates of losses are available for Rhizoctonia bare patch of wheat in Australia, sheath blight of rice in Asia and cotton seedling disease in the USA. The remainder of the reports cited are for only a few crops in selected regions and in selected years.

Establish real-time monitoring models of cotton aphid quantity based on different leaf positions in cotton seedlings

Cotton aphids, Aphis gossypii glover, are major pest threats to cotton plants, leading to quality and yield loss of cotton. Rapid and accurate evaluation on the occurrence and quantity of cotton aphids can help precision management and treatment of cotton aphids. The occurrence rules of cotton aphids on different leaf positions in cotton seedling stage for two cultivars of cotton were studied. The quantity of cotton aphids in the whole cotton seedlings were predicted based on the single leaf cotton aphid quantity. The correlation analysis results showed that cotton aphids of single leaf were significantly and positively correlated with the infected time, the all leaves of the whole plant, the whole plant contained all leaves and branches. The variance analysis results showed that cotton aphids of single leaf were significant difference with the extension of infected time. Based on different leaf positions, monitoring models were constructed respectively. The modelling set’s determination coefficient of ‘Xinluzao-45’ was greater than 0.8, while ‘Lumainyan-24’ was greater than 0.6. The best monitoring leaf position was the third for ‘Xinluzao-45’, the sixth for ‘Lumianyan-24’. From the data analysis, we can realize that it is feasible to construct a monitoring model based on the occurrence of cotton aphid in one leaf in cotton seedling, and different cotton varieties have different leaf positions. This will greatly reduce the investment of manpower and time.

Exogenous melatonin improves salt stress adaptation of cotton seedlings by regulating active oxygen metabolism

Melatonin is a small-molecule indole hormone that plays an important role in participating in biotic and abiotic stress resistance. Melatonin has been confirmed to promote the normal development of plants under adversity stress by mediating physiological regulation mechanisms. However, the mechanisms by which exogenous melatonin mediates salt tolerance via regulation of antioxidant activity and osmosis in cotton seedlings remain largely unknown. In this study, the regulatory effects of melatonin on reactive oxygen species (ROS), the antioxidant system, and osmotic modulators of cotton seedlings were determined under 0–500 µM melatonin treatments with salt stress induced by 150 mM NaCl treatment. Cotton seedlings under salt stress exhibited an inhibition of growth, excessive hydrogen peroxide (H2O2), superoxide anion (O2−), and malondialdehyde (MDA) accumulations in leaves, increased activity levels of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), and elevated ascorbic acid (AsA) and glutathione (GSH) content in leaves. However, the content of osmotic regulators (i.e., soluble sugars and proteins) in leaves was reduced under salt stress. This indicates high levels of ROS were produced, and the cell membrane was damaged. Additionally, osmotic regulatory substance content was reduced, resulting in osmotic stress, which seriously affected cotton seedling growth under salt stress. However, exogenous melatonin at different concentrations reduced the contents of H2O2, O2−, and MDA in cotton leaves, increased the activity of antioxidant enzymes and the content of reductive substances (i.e., AsA and GSH), and promoted the accumulation of osmotic regulatory substances in leaves under salt stress. These results suggest that melatonin can inhibit ROS production in cotton seedlings, improve the activity of the antioxidant enzyme system, raise the content of osmotic regulation substances, reduce the level of membrane lipid peroxidation, and protect the integrity of the lipid membrane under salt stress, which reduces damage caused by salt stress to seedlings and effectively enhances inhibition of salt stress on cotton seedling growth. These results indicate that 200 µM melatonin treatment has the best effect on the growth and salt tolerance of cotton seedlings.

Physiological and Biochemical Properties of Cotton in Response to Copper Stress

Backgroundcopper (Cu) is an essential micronutrient, required for plant growth and development. However, high concentrations of Cu can be extremely toxic to plant. This study investigate the tolerance mechanism of cotton under copper stress and its potential for soil pollution improvement.ResultsThe hybrid cotton variety (Zhongmian 63) and its two parent lines were selected as materials. Cotton seedling were treated with different Cu concentrations (0, 0.2, 50, 100, 200 μM) for 10 days in hydroponic condition. The results showed that the stem height, root length, and leaf area of cotton seedlings appear to have a down trend with the increase of Cu concentration. Increasing Cu concentration promoted Cu accumulation in roots, stems, and leaves of all the three cotton genotypes, however, the roots region was the main Cu storage organ, followed by leaves and stems regions. Compared with the parent lines, the roots of Zhongmian 63 are more capable of enriching Cu and have the least amount of Cu transported to the shoots. Therefore, the toxicity of Cu to cotton seedling is effectively alleviated. Cu-caused oxidative stress to cotton leaves was evident by over accumulation of H2O2 and MDA. POD activity and soluble sugar content increased firstly and then decreased compared with the control group. GSH content increased and photosynthetic pigment content decreased with increasing copper concentration in nutrient solution. ConclusionOur results suggest that the hybrid cotton variety Zhongmian 63 performed well under Cu stress. This lays the theoretical foundation for further analysis on molecular mechanism of cotton resistance to copper and promoting the large-scale planting Zhongmian 63 in the copper-contaminated area.

Biochar effect - mediated ammonium transporter genes and GDH may be the core of improvement nitrogen assimilation in cotton seedling

Biochar enhancement of nitrogen efficiency in crops is highly essential not only to reduce costs of agricultural production but also to conserve resources, lower energy consumption for products of these fertilizers, strengthen soil health, and eventually helps in slowing climate change; however nitrogen efficiency physiology by biochar effects is not clear. Here, we reported on the morphological, nitrogen metabolism and cytokinin, at seedling stage, under different layers of biochar and limited urea conditions grown in soil culture. Expression profile of miRNAs and AOB was further studied in fine and medium roots. It showed active root absorption area, fresh weight, and nitrogen agronomic efficiency responded significantly under biochar and reduction by 20% urea condition in the surface soil layer. Also, NR and GPT activity in fine roots remarkably increased with cytokinin, but decreased significantly in medium roots, meanwhile both NR and GDH activity did so. GOGAT activity was to be dependent with biochar and urea locations. In addition, AMT1;1, gdh3 and gdh2 in fine roots showed their up-regulation with reduction 20% urea and biochar. It revealed that co-expression of gdh3 and gdh2 in fine roots significantly affected nitrogen assimilation under reduction 20% urea with biochar on surface soil at seedling stage.HighlightsThe co-expression of ammonium transporter gene and GDH induced by biochar effect improves nitrogen efficiency and seedling growth.These data emphasizes the importance of effects of cytokinin on nitrate reductase activity closely related to the position under biochar condition, which is a key element of enhancement nitrogen assimilation efficiency in cotton seedling.Biochar addition applied into 0 to 10cm soil had a more positive effect on seedling growth than that into 10 to 20cm soil layers.

IMPACT OF Al NANOPARTICLES ON CHLOROPHYLL PIGMENT CONTENT AND ENZYME ACTIVITY IN COTTON LEAVES

The role of nanotechnology in solving environmental problems is increasing, and there is a need for additional research in this area. One of these environmental problems is soil salinization. During salinity stress, germination, growth and development ofplants slow down, and the quantity of pigments, chlorophyll and carotenoids in leaves decreases. So does the activity of such important physiological processes as photosynthesis, respiratory processes and enzyme activity. There are several ways to improve the salt tolerance of cotton. The cotton varieties can be improved genetically, or another way is to increase the stability of seeds or seedlings by chemical, biological or physological methods. At the early stages of development cotton seedling are very sensitive to salinity and other stress factors. The study investigated the effect of Al nanoparticles on the pigment composition in cotton seedling leaves and on the enzyme activity (ascorbate oxidase, polyphenol peroxidase and guaiacol-dependent peroxidase) in soil samples, collected in different areas of the Mugan plain. It was found that cotton seeds develop well in saline soils if treated with Al nanoparticles. Significant changes were observed in the plant development and in the kinetics of physiological processes. The quantity of chlorophyll pigments a and b in cotton sprouts (mainly at three leaf stages) increased, and the change in enzyme activity occured. Thus, during salinity stress the influence of basic enzymes, such as ascorbic peroxidase, increased in sprouts but decreased in leaves if the cotton plants are cultivated in saline soils with Al nanoparticles. The decrease in the activity of polyphenol oxidase and guaiacol-dependent peroxidase was insignificant.