The Effects of Soil Solarization and Compost on Soil Suppressiveness against Fusarium Oxysporum f. sp. Melonis

Soil suppressiveness against Fusarium was tested using solarized and non-solarized soils combined with composts of three maturation levels, and a non-amended control. The soils were sampled on three dates: after previous year solarization but before current year solarization (0 weeks), at the end of the solarization period of the current year (4 weeks), and 4 weeks later (recovery time). Melon seedlings were inoculated with Fusarium spores and disease severity was assessed. The study showed a reduction of soil suppressiveness capacity against Fusarium oxysporum f. sp. melonis after 1 year of solarization (0 weeks). Fusarium disease severity in artificially inoculated melon plants, expressed by area under the disease progress curve, was higher in solarized soil than in non-solarized soil. Compost addition lowered the disease severity, both in the solarized and in the non-solarized soils. However, suppression was not obtained at the end of the solarization period, whereas compost beneficial effect was found at this time.     

Effect of Compost Properties on Progress Rate of Verticillium dahliae Attack on Eggplant (Solanum melongena L.)

Several composts were tested for their capacity to moderate the effect of Verticillium dahliae Kleb. (VCG B4, VD) on eggplant (Solanum melongena) under greenhouse conditions. Eggplants plantlets were inoculated by immersing their roots in conidial suspension and then planted in pots filled with mixtures of compost or peat moss, mixed with perlite. Six composts and peat moss mixtures were tested, of which tomato waste compost suppressed V. dahliae, and turkey litter compost partially suppressed it. Reduced levels of symptoms and lower fungal colonization were detected in the xylem of eggplants planted in tomato waste compost, and these plants accumulated more dry matter and had higher chlorophyll content compared to other media. However, survival of conidia in tomato waste compost showed only a moderate decrease compared with a sharp decrease in other media, suggesting that conidial eradication cannot be proposed as the suppressiveness mechanism. γ irradiation of tomato waste compost and peat at 2.5 Mrad reduced microorganism density by four orders of magnitude, but irradiation of tomato waste compost did not reduce its suppressiveness of V. dahliae. Composts properties affected progress rate of VD in the xylem tissue of eggplant seedling. These properties could indicate both biotic and abiotic factors affecting the process.     

A new potential therapeutic remedy against Aeromonas hydrophila infection in rainbow trout (Oncorhynchus mykiss) using tetra,Cotinus coggygria

Different antibiotic‐based drugs are being used for the treatment of Aeromonas hydrophila infection in rainbow trout, and several studies emphasize the use of medicinal plants as immunostimulants for prophylactic measure against Aeromoniasis disease. However, therapeutic effects of aqueous methanolic extracts of tetra (Cotinus coggygria) against A. hydrophila in rainbow trout were not investigated. Four different concentrations of tetra extract (0 [control], 4, 8 and 12 mg/100 µl) and also two different positive control groups (florfenicol and doxycycline antibiotics) were administered orally using feeding needles to individual rainbow trout, Oncorhynchus mykiss of all experimental groups twice a day after intramuscular inoculation of A. hydrophila. The study period was for 10 days. On 0th, 3rd, 7th and 10th day, blood and tissues were collected from the fish and changes in humoral immune responses, haematology and immune‐related gene expressions were determined. In the study, superoxide radical production was decreased generally in all experimental groups except in 12 mg tetra and florfenicol treatments compared to control (p < .05). Lysozyme activity was generally decreased (p < .05), or no differences were observed in all experimental groups compared to the control. Myeloperoxidase activity was significantly increased in florfenicol‐treated fish group on 7th day (p < .05). Generally, myeloperoxidase activity showed an increase in almost all tetra‐treated groups. Haematological parameters increased but were not significantly high enough in treatments. Almost all immune‐related gene expressions were significantly enhanced on 3rd and 10th day of the study. Survival rate of 53.33% was found in control group. There were no significant differences in survival between control and 4 mg tetra‐treated group (p > .05). All the other groups' survival rate was significantly increased compared to control. The highest survival rate was found in florfenicol group (80%). In 12 mg tetra‐, doxycycline‐ and 8 mg tetra‐treated groups, survival rate was recorded as 74.44%, 70% and 70%, respectively. Our results suggest that tetra methanolic extract is an effective therapeutic remedy against A. hydrophila infection in rainbow trout at the dose of 24 mg/32.34 g body weight/day.     

The interdependent effects of solar disinfestation and compost maturity level on soil microbial activity

The combined effects of soil solarization and application of compost of various maturity levels upon soil microbial activity were studied under field conditions during 2010–2012. Eight treatments were divided into solarized and non-solarized treatments, and each was either non-amended or annually amended with compost at 6 kg (DW) m^-2. The composts were mature, partially mature, or immature. In all three tested parameters of microbial activity (respiration rate, heat output, and dehydrogenase activity) the immature compost showed higher activity than the other compost types. Soil samples were collected weekly in order to assess microbial activity, which was evaluated from measurements of soil respiration rate, heat output, and dehydrogenase activity. Significant and year-to-year reproducible differences in all three parameters were observed between soils amended with the three compost types. Some residual (carry-over) effects of previous-year treatments were obtained. Microbial activity decreased in both solarized and non-solarized treatments during the experimental period, probably because of increasing summer temperatures, but the decline was sharper in the solarized treatments probably due to oxygen deficiency under the tarp. Significantly higher activity was found in the treatments amended with the immature compost, both in the solarized and non-solarized treatments. This could be a result of the high level of dissolved organic matter in the immature compost, which enhanced microbial activity.