Επίδραση καταπονήσεων στην ποιότητα και συντηρησιμότητα καρπών ροδακινιάς και ελιάς

Abstract

The effect of deficit irrigation and reflective mulch on quality and storage ability of peaches and green olives was studied for three consecutive growing seasons 2006, 2007 and 2008. For the experiments we used three farms in different locations (Velestino, Platanoulia and Anchialos) in Central Greece. In Velestino, we worked with ‘Royal Glory’ peaches and ‘Caldesi 2000’ nectarines. These cultivars ripen relatively early (late June – early July). We applied four treatments for each variety: a) control (C), irrigation applied at 100% of evapotranspiration (ETc); b) deficit irrigation (DI), irrigation at 75% of ETc in the last three weeks before harvest and 50% of ETc postharvest; c) reflective mulch Extenday® (Ref) underneath the tree canopy applied three weeks before harvest and remained until Fall; and d) the combined treatment of reflective mulch and deficit irrigation (RefDef). Quality was assessed in fruit harvested from upper and lower (shaded) part of tree canopy at harvest and after 2, 4, and 6 weeks of cold storage at 2 °C and one day shelf life. The fruit quality parameters we measured included: skin colour, flesh firmness and specific conductivity, acidity, soluble solids content (SSC), percentage of fruit dry mass, fruit weight, total phenolic content and subjectively chilling injury (CI). In addition, tree fruit production was estimated and solar radiation (UV and PAR) underneath the tree canopy was measured. With storage time in the two cultivars, skin colour slightly changed, fruit softened and the specific electric conductivity, SSC, acidity and percentage dry mass decreased, while total phenol content and CI symptoms increased. Reflective mulch application improved light availability, especially at the lower part of tree canopy. The different treatments applied had different effects on fruit quality in the twocultivars, but they didn’t affect tree productivity. Nectarines treated with DI had better quality at harvest and there were more sensitive in cold storage compared to the control fruit. Peaches grown in DI conditions had similar quality as the control fruit, except of the higher SSC and more CI symptoms. Nectarines from the reflective mulch treatment had more intense skin blush, firmer flesh, higher acidity and percentage dry mass, similar SSC and total phenol content, and more leatheriness (CI symptom) compared to control nectarines. Peaches from the reflective mulch treatment were more mature at harvest than fruit of other treatments and had better quality but shorter storage ability compared to control fruit. Fruit from the combined treatment, RefDef, behaved either like fruit from DI or like fruit from Ref treatment. Overall fruit quality was improved by different treatments applied, but fruit were more sensitive to cold storage than control fruit. Also in ‘Caldesi 2000’ nectarines cultivated in Velestino site, we studied the influence of the treatmentsmentioned above (C, DI, Ref, RefDef) on the content of individual phenolic groups at harvest and during storage for two consecutive years (2007 and 2008). For the quantitative analysis of phenolic compounds we used HPLCDAD and for the qualitative analysis HPLC-MS-MS. The individual phenolicgroups in the edible fruit part (skin + flesh) consisted mainly of proanthocyanidins (200 mg /100 g fresh weight - fw), lower concentrations of phenolic acids (17 mg /100 g fw) and minor quantities of flavonols (5 mg /100 g fw) and anthocyanidins (1.2 mg/100 g fw). DI increased the content of totalphenolics, including proanthocyanidins and phenolic acids, reaching similar amount in both years. Sun-exposed fruit (upper part of canopy) had higher phenolic compounds’ content than shaded fruit (lower part of canopy). However, reflective mulch significantly increased the content of total phenolics, particularly phenolic acids and proanthocyanidins, in fruit located in the lower part of the canopy. During storage, C, DI and Ref treatments did not seem to affect the content of phenolic acids, flavonols and proanthocyanidins in nectarines. Optimizing cultural practices through properirrigation and light distribution in the canopy can be a way to increase the phenolic content of nectarines. In Platanoulia farm, we worked with clingstone peach cultivars ‘Loadel’ and ‘Fortuna’, which ripen during the second half of July. The treatments we applied in this farm were exactly the same as at the Velestino farm. Fruit quality was performed initially at harvest and after 3 and 6 weeks cold storage plus 1 day shelf life. Quality measurements were exactly the same with thosewe measured in peaches from Velestino farm. Fruit were harvested at commercial maturity from throughout the canopy of the experimental trees. In both ‘Loadel’ and ‘Fortuna’ cultivars, cold storage caused partial fruit ripening and partial fruit quality loss, especially after six weeks of coldstorage and when chilling injury symptoms appeared. Reflective mulch application increased light availability especially in the lower part of tree canopy, as observed in Velestino farm. ‘Loadel’ peaches from DI trees seemed to have improved fruit quality compared to fruit from well-irrigatedtrees. On the other hand, DI in ‘Fortuna’ peaches seemed to delay ripening and, if these fruit were left for longer on the tree, they could develop better quality than fruit from well-irrigated trees. Reflective mulch seemed to improve ‘Loadel’ peach fruit quality mainly due to earlier ripening. ‘Fortuna’ peach fruit quality did not clearly benefit from reflective mulch. Generally, the treatments studied affected in different ways the fruit quality of the two cultivars studied, as the quality of ‘Loadel’ peaches improved because of DI and the reflective mulch treatments to a larger extend compared to the ‘Fortuna’ peaches. In Anchialos farm, two green table olive cultivars were tested,‘Konservolea’ and ‘Chondrolia Chalkidikis’ (from now on called Chondrolia). Six trees were the experimental units – replications per treatment. For ‘Konservolea’ there were four treatments: control, deficit irrigation (since mid July, i.e. during pit hardening and final flesh swelling when water was around 20% of the control), reflective (irrigated similarly to control and reflective mulch was installed under the tree canopy two months before harvest, i.e. mid July) and reflective deficit (the deficit irrigation treatment with a reflective mulch under the tree canopy). For ‘Chondrolia’ the treatments were only two, the control and the deficit ones (same conditions like cv Konservolea). Fruit quality evaluations took place at harvest and after cold storage (1, 2, 3, 4 and 5 weeks) plus 1 day shelf-life. Quality evaluation included skin colour, flesh firmness, % flesh dry matter and total phenol content. In addition, symptoms of chilling injury were estimated subjectively. At harvest, there were no differences in quality among the treatments in both cultivars except of the total phenol concentration in Chondrolia olives from DI treatment that was higher and remained higher during storage than the control fruit. With cold storage, quality decreased progressively, because of the severity of chilling injury symptoms in all treatments. Flesh firmness changed depending on theseverity of chilling injury symptoms. When slight symptoms were found, flesh firmness decreased, but, with severe CI symptoms, flesh dryness caused an increase in flesh firmness. Flesh phenols decreased with storage time probably due to their use for tissue browning due to chilling injury damage. In fruit from both olive cultivars, DI resulted in increased % dry mass content in theflesh compared to olives from well-irrigated trees, probably resulting in better final processed product. In ‘Konservolea’ olives, DI did not negatively affect any fruit quality parameter compared to olives from well-irrigated trees. On the opposite, in ‘Chondrolia’ olives, deficit irrigation resulted in more chilling injury prone olives compared to olives from control trees and this sensitivity was depicted from many parameters studied, i.e. skin color indexes a* and hue, flesh firmness and phenol content. Reflective mulch application did not affect fruit quality and storage ability besides that it increased % flesh dry matter. Generally, fresh ‘Chondrolia’ green olives were more sensitive to cold storage than ‘Konservolea’ olives although they were cultivated in the same orchard. In conclusion, with the appropriate cultivation practises (deficit irrigation and reflective mulch applications), we can reduce the amount of water used for irrigation and in the same time produce fruit with better than or similar quality to the control fruit.

Στην παρούσα εργασία μελετήθηκε η επίδραση της ελλειμματικής άρδευσης και του ανακλαστικού πλαστικού (με σκοπό τη μείωση χρήσης αρδευτικού νερού και βελτίωση του φωτισμού της κόμης) στην ποιότητα των καρπών ροδακινιάς ‘Royal Glory’, νεκταρινιάς ‘Caldesi 2000’ και συμπύρηνωνροδάκινων ‘Loadel’ και ‘Fortuna’ καθώς και πράσινου καρπού ‘Κονσερβολιάς’ και ‘Χονδρολιάς Χαλκιδικής’ κατά τη συγκομιδή και μετά από ψυχρή συντήρηση για τρεις συνεχόμενες καλλιεργητικές περιόδους 2006, 2007 και 2008. Οι παράμετροι ποιότητας που εξετάστηκαν περιλάμβαναν το βάρος καρπού, το χρώμα φλοιού, τη σκληρότητα σάρκας, την ειδική ηλεκτρική αγωγιμότητα και το ποσοστό ξηρού βάρους, καθώς και τα διαλυτά στερεά συστατικά (ΔΣΣ), την οξύτητα και τα ολικά φαινολικά του χυμού. Επίσης, πραγματοποιήθηκε υποκειμενική εκτίμηση των ζημιών που εμφανίστηκαν από τη χαμηλή θερμοκρασία κατά τη συντήρηση, chilling injury (CI). Τέλος, πραγματοποιήθηκαν μετρήσεις εκτίμησης παραγωγής των δένδρων και μετρήσεις ηλιακής ακτινοβολίας (UV και PAR) στην κατώτερη κόμη των δένδρων. Η εφαρμογή των διαφορετικών μεταχειρίσεων επηρέασε διαφορετικά την ποιότητα των καρπών των διαφορετικών ειδών και ποικιλιών που μελετήθηκαν, αλλά δεν έδειξε να επηρεάζει αρνητικά την παραγωγή τους. Γενικά η ποιότητα των καρπών βελτιώθηκε με τις διαφορετικές μεταχειρίσεις που εφαρμόστηκαν, αλλά μειώθηκε η συντηρησιμότητα τους. Οι επιμέρους για κάθε ποικιλία μεταβολές λόγω των μεταχειρίσεων και της συντήρησης περιγράφονται σε αντίστοιχα κεφάλαια. Παράλληλα, μελετήθηκεη επίδραση της ελλειμματικής άρδευσης και του ανακλαστικού πλαστικού εδαφοκάλυψης στη συγκέντρωση των βιοενεργών ουσιών μόνο στα νεκταρίνια ‘Caldesi 2000’ στη συγκομιδή και κατά την ψυχρή συντήρηση για δύο έτη (2007, 2008). Ο διαχωρισμός των ουσιών πραγματοποιήθηκε μεχρωματογραφία αντίστροφης φάσης (HPLC-DAD) και η ποιοτική ανάλυση των ουσιών με χρωματογραφία μάζας (HPLC-MS-MS). Οι επιμέρους ομάδες των φαινολικών ουσιών που περιέχονται στο εδώδιμο τμήμα (σάρκα και φλοιός) των νεκταρινιών ‘Caldesi 2000’ αποτελούνται κυρίως απόπροανθοκυανιδίνες, σε μικρότερη συγκέντρωση φαινολικά οξέα και, σε πιο μικρές συγκεντρώσεις, φλαβονόλες και ανθοκυανιδίνες. Συμπερασματικά, θα μπορούσαμε να πούμε ότι βελτιστοποιώντας τις καλλιεργητικές πρακτικές - εξοικονόμηση αρδευτικού νερού και εφαρμογή ανακλαστικού πλαστικούμπορούμε να αυξήσουμε τη συγκέντρωση των φαινολικών ουσιών στα νεκταρίνια έχοντας σαν αποτέλεσμα παραγωγή καρπών υψηλής διατροφικής αξίας.