Physiological Disorders and Fruit Quality Attributes in Pomegranate: Effects of Meteorological Parameters, Canopy Position and Acetylsalicylic Acid Foliar Sprays

Abstract

Meteorological parameters and occurrences of cracking (CR), russeting (RS), and sun scald (SS) symptoms were monitored in a pomegranate cv. “Wonderful” orchard planted in a W–E orientation, during a 3-year study. Moreover, the efficacy of preharvest foliar sprays with acetylsalicylic acid (ASA; 0.5 mM or 1.0 mM), applied biweekly four to six times, on yield and fruit quality attributes were evaluated in a 2-year study. Fruit from the N-side of the canopy had greater CR and RS, whereas SS symptoms were lower, compared with the S-exposed part of the canopy. The N-side of the canopy had also substantially lower fruit number and yield, suggesting for an important role of light on bisexual flower formation and/or fruit set. Following the occurrences in CR and RS during the fruit maturation period, it was found that temperature fluctuation was the main cause. The presence of RS damages may also be related with increased relative humidity and water movement as symptoms were higher in years with higher values, in the N-side of the canopy and often occurred in the exposed and stylar end of the fruit. The ASA treatment substantially reduced RS by up to 57%, improved the peel red coloration, while anthocyanin, antioxidant capacity, and soluble solid contents in juice were higher. Foliar sprays with ASA did not affect yield, but induced a trend of bigger-sized fruit. In conclusion, planting in a N–S row orientation and selecting an orchard plantation site with a minimum temperature fluctuation and low relative humidity during the fruit-ripening period are measures to control CR and RS in pomegranate. ASA foliar applications proved to have beneficial effects on juice antioxidant contents, but more importantly on fruit appearance.

Fruit Quality Traits and Genotypic Characterization in a Pomegranate Ex Situ (Punica granatum L.) Collection in Greece

“…Variations are expected to occur not only due to genotypic differences but also due to environmental factors; higher temperatures are expected to result in higher TSS, lower TA and lower red coloration [53]. Moreover, in Northern Greece due to adverse weather condition during the fruit maturation period in October, such as temperature drop and rain, causing cracking and russeting damages, harvest is often forced to avoid damages [54]. In California, the harvest of Wonderful is recommended to start at TSS 17.0 • Brix and TA 1.9% [55] whereas in the present study it had relatively lower TSS and greater TA (16.3 • Brix and 2.2%, respectively).…”

Pomegranate Fruit Growth and Skin Characteristics in Hot and Dry Climate

“…Fluctuations in maximum temperature and lower humidity have been positively correlated with pomegranate cracking at the end of growth ( Drogoudi et al, 2021 ). In Israel, russeting due to microcracks develops at mid-growth around August-September, and may be related to the heat waves described above.…”

“…Symptoms of cracking and russeting in pomegranate develop first as tiny cracks in the cuticle, and cv. “Wonderful” appears to be more susceptible to this than other cultivars ( Drogoudi et al, 2021 ). This could be due to the different timing of its fruit set and harvest—“Wonderful” is a late cultivar.…”

Preharvest Foliar Salicylic Acid Sprays Reduce Cracking of Fig Fruit at Harvest

“…In other fruit species, SA have earlier been associated primarily with alleviation of peel damage though no effect on cracking incidence has been reported apart from the minimal effect on pomegranates found in one case in a study [29]. Recently, preharvest salicylate application prevented russeting (i.e., microscopic cracks in the cuticle and a corky-like peel area beneath them), but did not reduce cracking in pomegranates [20]. In loquat, preharvest salicylate application did not affect cracking incidence or purple spot disorder [38].…”

“…In other crops, exogenous application of salicylates during cultivation has been associated with improved fruit quality. For instance, they alleviated chilling injury symptoms [19] and peel russeting [20] in pomegranate, and prevented wax loss in blueberry [21]. Furthermore, salicylate application increased anthocyanin synthesis and total antioxidant capacity, as in plum [22] and grape [23], although not apparent in tomato under certain conditions [24].…”