Browsing by Author "Naranjo, P."

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    Diaporthe species identified from postharvest rot on kiwifruits during long term storage
    (American Phytopathological Soc, 2014) Díaz, G. A.; Latorre Guzmán, Bernardo; Jara, S.; Ferrada, E.; Naranjo, P.; Zoffoli Guerra, Juan Pablo
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    Effects of gibberellic acid on the rheological properties of sweet cherry tissue
    (2017) Zoffoli Guerra, Juan Pablo; Naranjo, P.; Hanssens, C.; Param, N.
    The application of gibberellic acid (GA3) has been well documented in the literature to enhance the size, firmness and soluble solid accumulation in sweet cherry, but there is little information regarding the effect of GA3 on the rheological properties associated with the impact and compression damage sensitivity of the tissue. GA3 application was evaluated on 'Bing' and 'Sweetheart' sweet cherry cultivars in two separate experiments. In 'Bing' the effect of a single application of 30 ppm of GA3 at either the straw-color or pit-hardening stages was compared with the effect of half of the concentration (15 ppm) being applied at both physiological stages. 'Sweetheart' was treated with 15 or 20 ppm of GA3 at the straw-color and pithardening stages, which was compared with a single application of 25 ppm of GA3 at the straw-color stage. In both experiments, untreated fruits were used as the controls. The soluble solid accumulation and fruit size distribution were determined at harvest. The rheological properties were characterized using the curve of strain vs. stress, obtained by a texturometer. Impact and compression damages were induced in the laboratory, and the incidence and severity of injured tissues were determined after 10 days at 0 degrees C. The fruit size was improved and the fruit tissue was less sensitive to compression and impact damage following gibberellic acid treatment. 'Sweetheart' was more sensitive to impact and compression damage and had lower values of rheological parameters than 'Bing'. The timing of GA3 applications demonstrated that the application of 15 ppm of GA3 at both the pit-hardening and straw-color stages was more effective for improving the size and soluble solid accumulation and reducing the sensitivity of the tissue to injury than a single application of 30 ppm of GA3 at either the straw-color or pit-hardening stages in 'Bing' or of 25 ppm at the straw-color stage in 'Sweetheart'.
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    First report of diaporthe novem causing postharvest rot of kiwifruit during controlled atmosphere storage in Chile
    (The American Phytopathological Society, 2014) Díaz, G. A.; Latorre Guzmán, Bernardo; Jara, S.; Ferrada, E.; Naranjo, P.; Rodríguez, J.; Zoffoli Guerra, Juan Pablo
    Chile is considered the third major exporter of kiwifruits (Actinidia deliciosa (A. Chev.) C. F. Liang & A. R. Ferguson) worldwide after Italy and New Zealand (1). The genus Diaporthe Nitschke (anamorph: genus Phomopsis) has been reported as causing postharvest rot in kiwifruit (4). During the current study, 1,400 fruits arbitrarily collected from seven controlled atmosphere (CA) rooms after 90 days of storage conditions (2% O2, 5% CO2) determined that 21.5% of the fruit were affected by decay and 0.86% developed symptoms different than those caused by Botrytis cinerea, the main postharvest pathogen associated to kiwifruit. Symptoms were soft rot with brown skin that started at the stem-end and in severe cases affected the entire fruit. Internally, affected fruit showed browning and watery tissues. Twelve affected fruits were surface disinfested (75% ethanol) and small pieces of internal rotten tissues were placed on acidified potato dextrose agar (APDA) for 7 days at 20°C. Twelve isolates were obtained, and four of them were identified morphologically and molecularly as Diaporthe ambigua, a species that has been previously described causing rot in stored kiwifruits in Chile (2). However, eight other flat, white to grayish colonies with sparse dirty-white aerial mycelium at the edge of the dish were obtained (3). Black pycnidia contained unicellular, hyaline, biguttulate, oval to cylindrical alpha conidia, with obtuse ends of (7.9) 6.7 (5.3) × (2.9) 2.5 (2.1) μm (n = 30). These isolates were tentatively identified as a Diaporthe sp. The species identification was determined by sequencing comparison of the internal transcribed spacer (ITS1-5.8S-ITS2) region of the rDNA (GenBank Accession Nos. KJ210020 to 24, KJ210027, and KJ210033) and a portion of beta-tubulin (BT) (KJ210034 to 38, KJ210041, and KJ210047) using primers ITS4-ITS5 and Bt2a-Bt2b, respectively. BLAST analyses showed 99 to 100% identity with D. novem J.M. Santos, Vrandecic & A.J.L Phillips reference ex-type (KC343156 and KC344124 for ITS and BT, respectively) (3). Eighteen mature kiwifruits cv. Hayward were inoculated using a sterile cork borer on the surface of the fruit and placing 5-mm agar plugs with mycelial of D. novem (DN-1-KF). An equal number of fruits treated with sterile agar plugs were used as negative controls. After 30 days at 0°C under CA, all inoculated fruit showed rot symptoms with lesions 7.8 to 16.4 mm in diameter. The same D. novem isolate was inoculated with 30 μl of a conidial suspension (106 conidia/ml) on the surface of 18 ripe kiwifruits that were previously wounded and non-wounded as described above. An equal number of wounded and non-wounded fruits, treated with 30 μl sterile water, were used as negative controls. All inoculated wounded fruits developed rot symptoms with necrotic lesions of 14.1 to 20.2 mm of diameter after 14 days at 25°C. Inoculated non-wounded and negative control fruits remained symptomless. Koch's postulates were fulfilled by re-isolating D. novem only from the symptomatic fruits. To our knowledge, this is the first report of rot caused by D. novem on kiwifruit during cold storage in Chile and worldwide. Therefore, both Diaporthe species appears to be associated to Diaporthe rot of kiwifruit in Chile.
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    First Report of Monilinia fructicola causing brown rot on stored Japanese plum fruit in Chile.
    (2014) Latorre G., Bernardo; Díaz Ulloa, Gonzalo Alberto; Valencia Díaz, Ana Luisa; Naranjo, P.; Ferrada, Enrique E.; Torres, R.; Zoffoli, Juan Pablo
    In autumn 2013, fruit of Japanese plum (Prunus salicina) cvs. Angelino and Black Kat developed an unusual brown and soft rot after 2 months in cold storage (0°C) on nearly 1% of the fruit. Fruit showed small, circular, light brown spots that eventually destroyed the entire fruit. Small sporodochia appeared on the fruit surface. Fruit was harvested from orchards located near San Francisco de Mostazal (33°59′ S, 70°41′ W), Chile. Small pieces of diseased tissue were selected from margins of lesions of surface disinfected (96% ethanol) fruit (n = 7) and placed on acidified potato dextrose agar (PDA) plates for 5 days at 20°C. Light brown colonies with even margins and concentric rings of spores were obtained. The conidia of five isolates were one-celled, hyaline, lemon-shaped, (min. 10.7) 14.9 ± 1.5 (max. 18.6) × (min. 8.1) 9.4 ± 0.8 (max. 10.8) μm (n = 30), and borne in branched monilioid chains. This fungus was identified as Monilinia fructicola (G. Winter) Honey (1). Identification was confirmed by amplifying and sequencing the ribosomal ITS1-5.8S-ITS2 region using ITS1 and ITS4 primers (3). BLAST analysis of Chilean plum isolates (GenBank Accession Nos. KF148610 and KF148611) were 99 to 100% identical to isolates of M. fructicola originating from the United States (DQ314727 and HQ846966, respectively) and 100% identical to the first Chilean isolate (JN001480) found in nectarines originating from California at the supermarkets in Santiago in June 2009. Koch's postulates were fulfilled by reproducing brown rot symptoms on mature wounded Japanese plums cv. Angelino (n = 8) inoculated with 10 μl of a conidial suspension (105 conidia/ml) or with a mycelium plug (5-mm diameter). After 2 days in humid chambers (>80% relative humidity) at 25°C, all inoculated fruit developed brown rot symptoms with necrotic lesion means of 15.8 and 21.5 mm in diameter in fruit inoculated with conidia and mycelium, respectively. Non-inoculated control fruit remained healthy. Re-isolations were performed on PDA and the presence of M. fructicola was morphologically confirmed in 100% of the symptomatic fruits. To our knowledge, this is the first report demonstrating the presence of M. fructicola causing brown rot in stored Japanese plums in Chile after its first interception in 2009 in Chile, suggesting that this pathogen has been established in the field. Currently, M. fructicola is a quarantine organism under official control, restricted to Prunus orchards between Santiago and Nancagua in central Chile (2).
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    Understanding postharvest quality of kiwifruit in relation to shoot and cane vigor
    (2015) Zoffoli Guerra, Juan Pablo; Naranjo, P.; Cuevas, A.
    Global kiwifruit production has expanded considerably. Over-softening and a low soluble solids concentration of kiwifruit after storage are the main factors associated with market satisfaction. Variability between kiwifruit batches, which is associated with season, orchard, pre- and postharvest practices, can result in fruit with unpredictable postharvest quality. The origin of fruit from different locations on a vine was used to explain the variation at harvest and postharvest quality. Fruit selected from different associations between shoot and cane vigor (evaluated by diameter) from vines of three orchards with demonstrated that fruit growing on terminated shoots was dominant. In addition, dry matter concentration and ripe soluble solids concentration were not affected by cane or shoot diameter. Further, fruit size was positively related to terminated shoot length and firmer fruit developed on non-terminated shoots compared with terminated shoots when assessed after ripening. These data were validated during the following year using data collected from eight orchards. Here, a comparison of fruit from non-terminated shoots with a small diameter (8.1-9.6 mm) growing on medium-diameter canes (22.4-24.5 mm) and from terminated shoots with a medium diameter (10.7-11.7 mm) growing on small-diameter canes (15.2-15.9 mm) demonstrated that terminated shoots produced softer fruit, and the nitrogen concentration in the pulp of these kiwifruits at harvest was negatively correlated with fruit firmness measured after 75 days at 0 degrees C + 4 days at 20 degrees C.