ARI Biennial Review for 2018-2019

Morphological and physiological responses induced by protein hydrolysate-based biostimulant and nitrogen rates in greenhouse spinach Plant-derived protein hydrolysates (PHs) are gaining prominence as biostimulants due to their potential to improve yield and nutritional quality even under suboptimal nutrient regimens. In this study, we investigated the effects of foliar application of a legume-derived PH (0 or 4 mL L -1 ) on greenhouse baby spinach ( Spinacia oleracea L.) under four nitrogen (N) fertilisation levels (0, 15, 30, or 45 kg ha -1 ) by evaluating morphological and colorimetric parameters, mineral composition, carbohydrates, proteins, and amino acids. The fresh yield in untreated and biostimulant-treated spinach plants increased in response to an increase in N fertilisation from 1 up to 30 kg ha -1 , reaching a plateau thereafter indicating the luxury consumption of N at 45 kg ha -1 . Increasing N fertilisation rate, independently of PH, lead to a significant increase of all amino acids with the exception of alanine, GABA, leucine, lysine, methionine, and ornithine but decreased the polyphenols content. Interestingly, the fresh yield at 0 and 15 kg ha -1 was clearly greater in P-treated plants compared to untreated plants by 33.3% and 24.9%, respectively. This was associated with the presence in of amino acids and small peptides PH ‘Trainer®’, which act as signaling molecules eliciting auxin- and/or gibberellin-like activities on both leaves and roots, and thus inducing a “nutrient acquisition response” that enhances nutrients acquisition and assimilation (high P, Ca, and Mg accumulation), as well as an increase in the photochemical efficiency and activity of photosystem II (higher SPAD index). Foliar applications of the commercial PH decreased the polyphenols content, but, on the other hand, strongly increased total amino acid content (+45%, +82%, and +59% at 0, 15, and 30 kg ha -1 , respectively) but not at a 45 kg ha -1 rate. Overall, the use of PH could represent a sustainable tool for boosting yield and nitrogen use efficiency and coping with soil fertility problems under low input regimens. (M.C. Kyriacou, G.A. Soteriou) Preharvest and postharvest evaluation of green asparagus male hybrid cultivars for intensive culture under local conditions Green asparagus Asparagus officinalis cultivation presents unique features which render it potentially suitable as an alternative crop for Cyprus. It is a crop species considered highly tolerant to drought, however its irrigation requirements during the growth period of the fern (i.e. the above ground vegetative part) are linked to yield and quality. To examine the prospects of green asparagus cultivation in Cyprus, the Vegetable Crops Section of the ARI, in collaboration with the Horticulture Laboratory, Aristotle University of Thessaloniki, has set up an experimental trial on five promising male hybrids of green asparagus. Expected outputs of the experiment are: a) The determination of earliness, yield and quality of the physicochemical characteristics and postharvest performance of the five promising male asparagus hybrids, and b) evaluation of the hybrids as to their suitability for cultivation in arid climate. Preliminary results showed no differentiation among cultivars, concerning extra yield (tn ha -1 ), total yield (classes extra & I), mean spear weight or extra spear number ( Table 3 ). ‘Giove’ produced the lowest I (class I) yield and I spear number among the cultivars. No differences were recorded among the cultivars concerning classes extra and I spear weight. (G.A. Soteriou, M.C. Kyriacou) . Table 3 . Mean comparisons for asparagus category Extra and I spear number, spear yield and spear mean weight obtained from asparagus cultivars ‘Eros’, Giove’, Vittorio’, ‘Italo’ and ‘Ercole’. 27 VEGETABLE CROPS ns= non-significant effect; * significant effect at the 0.05 level; ** significant effect at the 0.01 level; *** significant effect at the 0.001 level. Values within columns followed by the same letter are not significantly different according to Tukey-Kramer HSD Test (P < 0.05).