Browsing by Author "Díaz, G. A."

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    Current status of kiwifruit arm dieback in Chile
    (American Phytopathological Soc., 2015) Díaz, G. A.; Lolas, M.; Latorre Guzmán, Bernardo; Zoffoli Guerra, Juan Pablo
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    Detection of Speck rot on Pink Lady apple fruit in the Maule Region in Chile
    (American Phytopathological Soc., 2015) Díaz, G. A.; Latorre Guzmán, Bernardo; Zoffoli Guerra, Juan Pablo; Cáceres, M.; Méndez, R.; Lolas, M.
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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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    First Report of Cadophora malorum Associated With Cordon Dieback in Kiwi Plants in Chile
    (The American Phytopathological Society (APS), 2016) Díaz, G. A.; Lolas, M.; Ferrada, E. E.; Latorre Guzmán, Bernardo; Zoffoli Guerra, Juan Pablo
    Chile is the third largest exporter of fresh kiwifruit (Actinidia deliciosa A. Chev.) worldwide, with over 10,000 ha cultivated. Cordon dieback of kiwi plants has increased considerably during the last decade in Chile. Symptoms include short internodes with small, chlorotic leaves, death of cane tips, and cordon dieback. Symptomatic cordons exhibited hard, brown, irregular cankers comprising between 5 to 45% of the cross section. An incidence of 25 to 75% of plants showing dieback symptoms was estimated (175 to 320 plants were observed per orchard) during a survey in seven commercial cv. Hayward orchards (>7 years old), located between Rancagua (34°00′ S) and Linares (35°48′ S), in 2013 and 2014. Symptomatic cordons (n = 82) were collected and cut into 5-cm2 pieces, surface disinfested with 96% ethanol for 10 s, and flamed for 8 s. Small wood pieces (2 to 3 mm) were taken from the edge of necrotic and healthy tissue, and plated on potato dextrose agar (PDA) amended with antibiotics and Igepal (Díaz and Latorre 2014). Grayish colonies (n = 18), with a Cadophora-like growth, were obtained after 21 days at 20°C. The remaining samples were in the Diaporthaceae and Botryosphaeriaceae families. On PDA, colonies grew slowly and exhibited a woolly to cottony center with regular white margins, and produced a yellow pigmentation. Microscopically, short, erect conidiophores had simple, hyaline or slightly pigmented erect monophialides, with single terminal collarettes. Conidia (n = 30) were hyaline, unicellular, oblong to ellipsoidal, biguttulate and, measured (1.7) 2.3 (3.6) × (3.7) 6.1 (7.8) µm (Gams 2000). Based on Travadon et al. (2015), three loci (ITS, β-tubulin, and EF1-α) were used for further molecular identification, using primers ITS4/ITS5, Bt2a/Bt2b and EF1-728F/EF1-986R. The sequences of four isolates were deposited in GenBank (Accession Nos. KT358979 to KT358982, KU532780 to KU532783, and KU532851 to KU532854 for ITS, β-tubulin, and EF1-α, respectively). BLAST analyses showed 99 to 100% identity with Cadophora malorum (Kidd & Beaumont) W. Gams (isolate CBS 165.42 ex-type, Accession Nos. AY249059, KM497134, and KM497090). Pathogenicity tests were conducted on kiwifruit canes (n = 16) and trunks (n = 10) of 15- and 3-year-old, respectively, Hayward vines during the winter months. The tips of the canes were pruned and 20 µl of a conidial suspension (106 conidia/ml) were placed on each pruning wound. Trunk inoculations were conducted at the base by creating a wound with a 5-mm-diameter cork borer and inserting a 5-mm mycelial plug, taken from 21-day-old cultures on PDA. An equal number of canes and trunks injured and treated with sterile agar plugs were used as negative controls. Vascular necrotic lesions of 111 and 62 mm in length developed on inoculated canes and trunks after 9 and 12 months, respectively, under field conditions. Lesions and dieback symptoms were observed in canes and trunks inoculated with C. malorum. Negative controls remained symptomless. Cadophora malorum was reisolated only from symptomatic canes and trunks. To our knowledge, this is the first report of C. malorum associated with cordon dieback in kiwi plants in Chile. Previously, C. malorum, C. luteo-olivacea, and C. melinii have been reported causing wood canker in kiwi plants (Prodi et al. 2008). These results require additional research to understand the role of C. malorum in the fungal complex associated with cordon dieback in kiwi in Chile.
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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.