Stefano Speca

Influence of phosphorus management on melon (Cucumis melo L.) fruit quality

BACKGROUND At harvest time, melon quality is related to internal and external parameters, which are very important for consumer attractiveness and marketable yield. Several agronomic factors can affect the quality of melon fruits and among them mineral availability may play a significant role. Therefore the aim of the work was to investigate the effect of phosphorus fertigation on melon fruit (Cucumis melo L.) qualitative characteristics, such as fruit size and yield, pulp colour and firmness, aroma and taste, as well as the accumulation of bioactive antioxidant compounds, namely phenols and carotenoids, and their antiradical properties. RESULTS Results allowed us to extrapolate the optimal P doses to be used for melon fertigation, to achieve high yield and fruit quality characteristics. Modelling the optimal P dose allowed us to maximize yield and resulted in around 257 kg P2 O5 ha(-1) , even if the quality indices relating to carotenoid content, texture and colour of the melon flesh were not significantly different between samples fertigated with the two highest levels tested. CONCLUSION It can be assumed that the level of 200 kg P2 O5 ha(-1) would be a good compromise between optimization of agronomic performance and melon fruit quality.

Proteomics of Durum Wheat Grain during Transition to Conservation Agriculture.

Nitrogen management in combination with sustainable agronomic techniques can have a great impact on the wheat grain proteome influencing its technological quality. In this study, proteomic analyses were used to document changes in the proportion of prolamins in mature grains of the newly released Italian durum wheat cv Achille. Such an approach was applied to wheat fertilized with urea (UREA) and calcium nitrate (NITRATE), during the transition to no-till Conservation Agriculture (CA) practice in a Mediterranean environment. Results obtained in a two-years field experiment study suggest low molecular weight glutenins (LMW-GS) as the fraction particularly inducible regardless of the N-form. Quantitative analyses of LMW-GS by 2D-GE followed by protein identification by LC-ESI-MS/MS showed that the stable increase was principally due to C-type LMW-GS. The highest accumulation resulted from a physiologically healthier state of plants treated with UREA and NITRATE. Proteomic analysis on the total protein fraction during the active phase of grain filling was also performed. For both N treatments, but at different extent, an up-regulation of different classes of proteins was observed: i) enzymes involved in glycolysis and citric acid cycles which contribute to an enhanced source of energy and carbohydrates, ii) stress proteins like heat shock proteins (HSPs) and antioxidant enzymes, such as peroxidases and superoxide dismutase which protect the grain from abiotic stress during starch and storage protein synthesis. In conclusion N inputs, which combined rate with N form gave high yield and improved quality traits in the selected durum wheat cultivar. The specific up-regulation of some HSPs, antioxidant enzymes and defense proteins in the early stages of grain development and physiological indicators related to fitness traits, could be useful bio-indicators, for wheat genotype screening under more sustainable agronomic conditions, like transition phase to no-till CA in Mediterranean environments.