Effect of organic agronomic techniques and packaging on the quality of lamb's lettuce.

BACKGROUND: This research focused on the effect of organic production systems on initial quality and postharvest performance of lamb's lettuce leaves stored in air or under modified atmosphere at refrigerated temperature. Different strategies of organic soil fertility management were compared under the same environmental conditions: (i) a simplified organic production system based on organic commercial fertilizers to recover crop uptake (SB); (ii) an organic production system based on organic matter amendment mainly supplied by animal manure (AM); and (iii) an organic production system based on organic matter amendment supplied by green waste compost (AC). Fully developed lamb's lettuce leaves were harvested and then packed into perforated bags (control in AIR) or in modified atmosphere packaging (MAP) and stored at 4 °C. RESULTS: At harvest, the yield of lamb's lettuce in the AM and AC systems was higher than that in SB. Phenol and dehydroascorbic acid accumulation was observed in the system with the lowest initial supply of organic amendment (SB). Regarding the effect of packaging, AIR conditions maintained the initial quality attributes for a longer period than MAP, which developed off-odours above the threshold of acceptability at 11 days, irrespective of the production system used. CONCLUSION: In general, the initial differences among the production systems were minimal during the postharvest storage. As for the tested packaging systems, AIR successfully maintained the initial quality attributes for a longer period than the MAP. © 2018 Society of Chemical Industry.

The Challenge of Peat Substitution in Organic Seedling Production: Optimization of Growing Media Formulation through Mixture Design and Response Surface Analysis.

Peat replacement is an increasing demand in containerized and transplant production, due to the environmental constraints associated to peat use. However, despite the wide information concerning the use of alternative materials as substrates, it is very complex to establish the best materials and mixtures. This work evaluates the use of mixture design and surface response methodology in a peat substitution experiment using two alternative materials (green compost and palm fibre trunk waste) for transplant production of tomato (Lycopersicon esculentum Mill.); melon, (Cucumis melo L.); and lettuce (Lactuca sativa L.) in organic farming conditions. In general, the substrates showed suitable properties for their use in seedling production, showing the best plant response the mixture of 20% green compost, 39% palm fibre and 31% peat. The mixture design and applied response surface methodology has shown to be an useful approach to optimize substrate formulations in peat substitution experiments to standardize plant responses.

Trichoderma harzianum T-78 supplementation of compost stimulates the antioxidant defence system in melon plants.

BACKGROUND: Compost is emerging as an alternative plant growing medium in efforts to achieve more sustainable agriculture. The addition of specific microorganisms such as Trichoderma harzianum to plant growth substrates increases yields and reduces plant diseases, but the mechanisms of such biostimulants and the biocontrol effects are not yet fully understood. In this work we investigated how the addition of citrus and vineyard composts, either alone or in combination with T. harzianum T-78, affects the antioxidant defence system in melon plants under nursery conditions. RESULTS: Compost application and/or Trichoderma inoculation modulated the antioxidant defence system in melon plants. The combination of citrus compost and Trichoderma showed a biostimulant effect that correlated with an increase in ascorbate recycling enzymes (monodehydroascorbate reductase, dehydroascorbate reductase) and peroxidase. Moreover, the inoculation of both composts with Trichoderma increased the activity of antioxidant enzymes, especially those involved in ascorbate recycling. CONCLUSION: Based on the long-established relationship between ascorbic acid and plant defence responses as well as plant growth and development, it can be suggested that ascorbate recycling activities play a major role in the protection provided by Trichoderma and its biostimulant effect and that these outcomes are linked to increases in antioxidant enzymes. We can conclude that the combination of citrus compost and T. harzianum T-78 constitutes a viable, environmentally friendly strategy for improving melon plant production.

qRT-PCR quantification of the biological control agent Trichoderma harzianum in peat and compost-based growing media.

To ensure proper use of Trichoderma harzianum in agriculture, accurate data must be obtained in population monitoring. The effectiveness of qRT-PCR to quantify T. harzianum in different growing media was compared to the commonly used techniques of colony counting and qPCR. Results showed that plate counting and qPCR offered similar T. harzianum quantification patterns of an initial rapid increase in fungal population that decreased over time. However, data from qRT-PCR showed a population curve of active T. harzianum with a delayed onset of initial growth which then increased throughout the experiment. Results demonstrated that T. harzianum can successfully grow in these media and that qRT-PCR can offer a more distinct representation of active T. harzianum populations. Additionally, compost amended with T. harzianum exhibited a lower Fusarium oxysporum infection rate (67%) and lower percentage of fresh weight loss (11%) in comparison to amended peat (90% infection rate, 23% fresh weight loss).