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Citrus nurseries significantly increase production costs due to the application of strictly technical and sanitary protocols. The growth media used are generally based on peat, a limited resource that is becoming increasingly scarce and consequently more expensive. Among the alternatives to peat is biochar, which could constitute a valid growing medium component for citrus seedling production. Three growth media were compared, each containing 50% sandy volcanic soil and the remaining 50% being: (i) biochar 50%; (ii) black peat 25% + biochar 25%; and (iii) black peat 25% + lapillus 25% as the control. The impact on the agronomic performance of citrus seedlings was assessed, and the involvement of specific genes in macronutrient uptake was evaluated. Destructive and molecular analyses were performed on leaves and roots during two different periods of the year: February and April. Based on physicochemical parameters and seedling growth, it can be assumed that peat can be partially substituted by conifer wood biochar in a total amount of 25 or 50%. A general comparison of the averages from the sampling and the various analyzed substrates revealed that in February, the evaluated genes involved in the absorption and transport of nutrients were differentially expressed in both leaves and roots, while in April, the expression was not consistent. Additionally, a general comparison between the analyzed tissues showed that, in most cases, expression was higher in the roots than in the leaves. Overall, a comparison among plants grown in different substrates indicated that the medium with 50% biochar displayed the highest expression levels. [ABSTRACT FROM AUTHOR]

Girdling is an ancient agronomic technique that causes a change in the distribution of photosynthates, mineral nutrients and plant hormones. The aim of this study was to assess the effect of girdling technique on 'Italia' and 'Victoria' table grape cultivars. In this study, the carpological, physico-chemical and sensory data were evaluated. In order to assess the effect of girdling on grape volatile compounds, a headspace solid-phase microextraction was also performed. Results showed the effects of girdling on morphological, physico-chemical and sensory characteristics of table grapes with a different change of berry size and colour depending on the cultivar. The girdling treatment produced a significant decrease of sugar content and total soluble solids/titratable acidity ratio only for 'Italia' cultivar. The analysis of volatile compounds revealed that 'Italia' cultivar had three more compounds than 'Victoria' and that the samples taken from the girdled grapevines had fewer compounds than their ungirdled ones. The results exhibited that the girdling treatment was more effective on the 'Italia' cultivar. This study showed that girdling efficacy strongly depends on the cultivar. The samples from the girdled grapevines had fewer volatile compounds than the ungirdled ones. The Principal Component Analysis totally differentiated both cultivar and treatment without overlap. [ABSTRACT FROM AUTHOR]

To investigate the influence of different types of fertilizers on quality parameters, N-containing compounds, and the delta(15)N, delta(13)C, delta(2)H, delta (34)S, and delta(18)O values of citrus fruit, a study was performed on the orange fruit cv. 'Valencia late' (Citrus sinensis L. Osbeck), which was harvested in four plots (three organic and one conventional) located on the same farm. The results demonstrated that different types of organic fertilizers containing the same amount of nitrogen did not effect important changes in orange fruit quality parameters. The levels of total N and N-containing compounds such as synephrine in fruit juice were not statistically different among the different treatments. The delta(15)N values of orange fruit grown under fertilizer derived from animal origin as well as from vegetable compost were statistically higher than those grown with mineral fertilizer. Therefore, delta(15)N values can be used as an indicator of citrus fertilization management (organic or conventional), because even when applied organic fertilizers are of different origins, the natural abundance of (15)N in organic citrus fruit remains higher than in conventional ones. These treatments also did not effect differences in the delta(13)C, delta(2)H, delta(34)S, and delta(18)O values of fruit.