Principles of Plant Breeding

An Improved Grading System For Measuring Plant Diseases Vol-36

Research on the mechanisms employed by the biocontrol agent Trichoderma virens to suppress cotton (Gossypium hirsutum) seedling disease incited by Rhizoctonia solani has shown that mycoparasitism and antibiotic production are not major contributors to successful biological control. In this study, we examined the possibility that seed treatment with T. virens stimulates defense responses, as indicated by the synthesis of terpenoids in cotton roots. We also examined the role of these terpenoid compounds in disease control. Analysis of extracts of cotton roots and hypocotyls grown from T. virens-treated seed showed that terpenoid synthesis and peroxidase activity were increased in the roots of treated plants, but not in the hypocotyls of these plants or in the untreated controls. Bioassay of the terpenoids for toxicity to R. solani showed that the pathway intermediates desoxyhemigossypol (dHG) and hemigossypol (HG) were strongly inhibitory to the pathogen, while the final product gossypol (G) was toxic only at a much higher concentration. Strains of T. virens and T. koningii were much more resistant to HG than was R. solani, and they thoroughly colonized the cotton roots. A comparison of biocontrol efficacy and induction of terpenoid synthesis in cotton roots by strains of T. virens, T. koningii, T. harzianum, and protoplast fusants indicated that there was a strong correlation (+0.89) between these two phenomena. It, therefore, appears that induction of defense response, particularly terpenoid synthesis, in cotton roots by T. virens may be an important mechanism in the biological control by this fungus of R. solani-incited cotton seedling disease.

Induction of terpenoid synthesis in cotton roots and control of Rhizoctonia solani by seed treatment with Trichoderma virens. [Erratum: 2003 Dec., v. 93, no. 12, p. 1606.]

The impact of biochar and chitosan on barley plants under drought stress conditions was investigated during two field experiments. Our results confirmed that drought stress negatively affected morphological and physiological growth traits of barley plants such as plant height, number of leaves, chlorophyll concentrations, and relative water content. However, electrolyte leakage (EL%), lipid peroxidation (MDA), soluble sugars, sucrose and starch contents significantly increased as a response to drought stress. Additionally, 1000 grain weight, grains yield ha−1 and biological yield significantly decreased in stressed barley plants, also anatomical traits such as upper epidermis, lower epidermis, lamina, and mesophyll tissue thickness as well as vascular bundle diameter of flag leaves significantly decreased compared with control. The use of biochar and chitosan led to significant increases in plant height, number of leaves, and chlorophyll concentrations as well as relative water content; nevertheless these treatments led to significant decreases in electrolyte leakage (EL%) and lipid peroxidation (MDA) in the stressed plants. Moreover, anatomical and yield characters of stressed barley plants were improved with application of biochar and chitosan. The results proved the significance of biochar and chitosan in alleviating the damaging impacts of drought on barley plants.

Beneficial Effects of Biochar and Chitosan on Antioxidative Capacity, Osmolytes Accumulation, and Anatomical Characters of Water-Stressed Barley Plants

The purpose of this study is to investigate the ability of specific fungus to biosynthesize copper oxide nanoparticles (CuO NPs) by the aid of gamma rays and evaluate its performance as a unique antimicrobial agent in the agricultural fields. CuO NPs were synthesized by Penicillium chrysogenum filtrate utilizing copper sulfate at various gamma rays doses. The identification was performed by UV-Vis., FTIR, XRD, DLS, TEM, SEM, EDX and mapping images. Antimicrobial potential of CuO NPs against selected crop pathogenic microbes had been estimated. From the results, the preferred doses applied for CuO NPs synthesis was recorded at 50.0 kGy. The proposed reaction mechanism was studied. TEM image with DLS analysis confirmed the morphology of CuO NPs possesses a mean diameter at 9.70 nm. CuO NPs exhibited a maximum antifungal activity against Fusarium oxysporum (37.0 mm ZOI) followed by Alternaria solani (28.0 mm ZOI), and Aspergillus niger (26.5 mm ZOI). On the other hand, it was active as antibacterial agent against Ralstonia solanacearum (22.0 mm ZOI) and Erwinia amylovora (19.0 mm ZOI). Therefore, due to these outstanding properties, CuO NPs may be utilized as the significant antimicrobial agents in the agricultural area to restrain the plant pathogenic fungi and bacteria from proliferation.

Penicillium chrysogenum -Mediated Mycogenic Synthesis of Copper Oxide Nanoparticles Using Gamma Rays for In Vitro Antimicrobial Activity Against Some Plant Pathogens

Powdery mildew is a potentially serious disease of Zinnia (Zinnia elegans). The disease is caused by theair-borne fungus Erysiphe cichoracearum and it is an occasional disease of Zinnia in Egypt. Culture filtrates ofTrichoderma harzianum, Epicoccum sp., Streptomyces endus and an actenomycetal isolate in addition to twoplant extracts i.e. miswak (Salvadora persica) and henna (Lawsonia inermis) were evaluated to control powderymildew disease of Zinnia plants. Culture filtrates of the aforementioned biocontrol agents were used as 25 and50%. Bioassays were conducted under field conditions during the two successive seasons of 2006 and 2007 atthe Experimental Farm of the Fac. of Agric., Kafr El-Sheikh Univ., Egypt to test the efficacy of these culturefiltrates applied to protect Zinnia plants from powdery mildew disease.Spraying zinnia plants four times, beginning from June 15th with one week interval by a hand atomizer underfield conditions with the previously culture filtrates and the two plant extracts gave sufficient control to powderymildew disease. The obtained results showed that, all used treatments led to significant decrease in both diseaseincidence and severity compared with control treatment. The highest disease incidence inhibition was obtainedwhen Epicoccum sp. and T. harzianum were used as 50% (v/v) sterilized water followed by henna and miswakextracts were used, respectively. Sprayed plants recorded best results for most growth characters, peroxidase(POX) and polyphenol oxidase (PPO) enzymes activity compared unsprayed one. In conclusion, biocontrolagents and some plant extracts can be substitutes to fungicides as an alternative and safe method for controllingpowdery mildew disease of Zinnia.

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Biological Control of Powdery Mildew on Zinnia (Zinnia elegans, L) Using Some Biocontrol Agents and Plant Extracts

Efficacy of certain bioagents on patho-physiological characters of wheat plants under wheat leaf rust stress

In an attempt to search for alternative control methods to pesticides, certain bio-control formulations (Bacillus subtilis 1, B. ubtilis 3, B. pumilus, Pseudomonas fluorescens and Epicoccum nigrum), bentocide, zinc oxide nanoparticles and nanosilica were tested against Cephalosporium maydis, the causative fungus of late wilt disease of maize, under field conditions of Kafr El-Sheikh Governorate, Egypt in 2011 and 2012 growing seasons. Results showed that the bio- control formulations were the most effective treatments against the disease, followed by nanosilica, bentocide and nanozinc oxide, descendingly in both growing seasons, with respect of pre-emergence damping off, disease incidence and crop yield. As well, the bio-control formulations showed the highest level of defense enzymes activity in maize post treatment, followed by nanosilica, nanoznic oxide and bentocide, descendingly in both seasons. Assayed materials represented potential effective alternatives to fungicides for controlling late wilt of maize.

Non-traditional methods for controlling maize late wilt disease caused by Cephalosporium maydis.

Some essential oils were evaluated as biocontrol agents against powdery mildew on Zinnia elegans, L A field experiment was carried out during the two successive seasons of 2006 and 2007 using marjoram, clove, cinnamon, garlic, ginger and fennel oils, added as foliar spray at 2 levels of 005 and 01 ppm besides Kema zein 75% and distilled water as a control Disease incidence and severity as well as other vegetative parameters such as plant height, number of branches per plant, leaf area, fresh and dry weights of shoots, root length and fresh and dry weights of roots were determined in the two seasons Also, peroxidase and polyphenol oxidase activities were determined after 24 hour from the last spray in leaves samples The highest significant decrease in disease incidence and severity and the best results for most studied growth and flowering parameters and total green colour were recorded with ginger, cinnamon and clove oils, respectively each at 01 ppm compared to the other treatments in both seasons In addition, the activities of peroxidase (POX) and polyphenol oxidase (PPO) enzymes were increased as a result of oils sprayed on plants These findings provide for a rational basis of a possible utilization of these essential oils as a safe and alternative method to fungicides for controlling powdery mildew of Zinnia plants

https://ccsenet.org/journal/index.php/jas/article/download/8401/6216

G. A. N. El-Kot

Papers

Biological Control of Powdery Mildew on Zinnia (Zinnia elegans, L) Using Some Biocontrol Agents and Plant Extracts

Efficacy of certain bioagents on patho-physiological characters of wheat plants under wheat leaf rust stress

Non-traditional methods for controlling maize late wilt disease caused by Cephalosporium maydis.

Efficacy of Some Essential Oils on Controlling Powdery Mildew on Zinnia (Zinnia Elegans, L.)

Biocontrol of Tilletia barclayana, the causal agent of kernel smut disease in rice.