RESUMO
During 2009 and 2010, a survey (n = 520) of diseased grapevines (Vitis vinifera L.) was done in vineyards located in Maipo and Colchagua valleys (33°43' to 34°36'S) in Chile. Symptoms of trunk diseases (TD) were observed on >10-year-old grapevines and consisted of short internodes, dead spurs and arms, and dieback. In cross sections, diseased arms and trunks exhibited brown, V-shaped cankers of hard consistency. Collected canker samples from cvs. Cabernet Sauvignon, Carménère, Red Globe, Syrah, and Thompson Seedless were surface sterilized in 75% ethanol for 45 s and plated onto potato dextrose agar modified with 0.005% tetracycline, 0.01% streptomycin, and 0.1% Igepal CO-630 (MPDA; Sigma-Aldrich, St. Louis, MO) for 7 days at 20°C. White-to-gray colonies with aerial mycelium growth turned dark gray after 3 to 5 days and tentatively identified as Botryosphaeriaceae. Hyphal tips of these colonies were transferred to MPDA and kept at 20°C with continuous light. After 30 days, colonies developed black, globose pycnidia with unicellular, hyaline, ellipsoidal, densely granulate, externally smooth, and thin-walled conidia that measured (16.3) 19.3 ± 2.3 (25.9) × (5.8) 7.4 ± 0.8 (9.2) µm (n = 20). Morphologically, these isolates were identified as Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips (2). Nucleotide BLAST analysis of the region ITS1-5.8S-ITS2 of rDNA of N. parvum isolates HMUC-104 and HMUC-105 (GenBank Accession Nos. JF273631 and JF273632) were amplified with ITS4 and ITS5 primers and revealed >99% similarity with the sequence of reference isolate (EU833984). Pathogenicity tests were conducted using isolates HMUC-104 and HMUC-105 on 30-day-old Carménère grapevines (n = 8) rooted in vitro by placing a 3- to 5-mm mycelial plug on the surface of the propagation medium. Additionally, detached green shoots (GS) (n = 5) and dormant canes (DC) (n = 6) 15-cm long were inoculated by placing a 3- to 5-mm mycelial plug underneath a cut aseptically made in the cortex. The GS and DC were placed in humidity chambers at 20 and 25°C, respectively. For controls, an equal number of rooted vines, in vitro vines, GS, and DC were treated with sterile agar plugs. Leaf number (LN), shoot length (SL), and root length (RL) were assessed on rooted plants in vitro after 30 days at 20°C. The extent of vascular discoloration (VD) of GS and DC were determined 15 and 45 days, respectively. N. parvum significantly (P < 0.05) reduced the LN, SL, and RL relative to the control plants. The length of VD varied from 54.86 to 55.39 mm and 14.8 to 15.48 mm in inoculated GS and DC, respectively. No VD symptoms were observed on the controls. N. parvum was reisolated from 100% of the inoculated in vitro plants, GS, and DC, completing Koch's postulates. N. parvum has been documented as a canker pathogen on V. vinifera and is known to contribute to the decline of grapevines. To our knowledge, this is the first report of N. parvum causing bot canker on grapevines in Chile, but has previously been reported in Australia, Spain, and the United States. Of 520 diseased plants in this study, 10 to 15% prevalence was estimated for TD and almost 2% prevalence was associated to N. parvum. Other Botryosphaeriaceae spp. were isolated with N. parvum from grapevine TD in Chilean vineyards (1,3,4). References: (1) J. Auger et al. Plant Dis. 88:1286, 2004. (2) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (3) B. A. Latorre et al. Phytopathology 76:1112, 1986. (4) A. Morales et al. Phytopathol. Mediterr. 49:112, 2010.
RESUMO
Blueberry (Vaccinium spp.) plantings have significantly increased in Chile during the last decade and, currently, over 10,700 ha are cultivated throughout the country. Among other diseases, stem canker and dieback has been frequently observed in commercial plantations with incidences between 15 and 45%. The aim of this study was to identify and characterize Neofusicoccum spp. causing stem canker and dieback of blueberry in Chile. Three species, N. arbuti, N. australe, and N. parvum, were identified based on colony and conidia morphology, and nucleotide sequence analysis of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2). These Neofusicoccum spp. were found alone or coexisting with Pestalotiopsis spp., Truncatella spp., or Phomopsis spp. Koch's postulates showed all Neofusicoccum spp. isolated from infected plants to be pathogenic when inoculated on blueberry fruit and twigs using both mycelia and conidia suspension. All blueberry cultivars tested, including, Brigitta, Bluecrop, Brightwell, Duke, Elliott, Misty, and O'Neal, were susceptible to Neofusicoccum spp. infection. Pathogenicity tests showed N. parvum to be the most virulent species and Elliott to be the most susceptible cultivar. This report represents the first description of N. arbuti, N. australe, and N. parvum as canker-causing agents on blueberry in Chile.
RESUMO
Phytophthora cryptogea was consistently isolated from diseased tissue taken from the crown and necrotic roots of grandiflora type petunia (Petunia × hybrida) that were collected in gardens in five public parks in Santiago, Chile in 2004 and 2005. Symptoms included leaf wilting and foliar chlorosis, followed by partial necrosis, and extensive dark-brown to reddish cankers in the crown. Disease incidence was over 50% and infected plants died within 7 to 10 days after transplanting. This pathogen was identified on the basis of colony morphology, morphological characterization of the sexual and asexual reproductive structures, and temperature range. The identification of Phytophthora cryptogea was further corroborated by the internal transcribed spacer sequence analysis (GenBank accession number EF093534). Isolates of P. cryptogea were pathogenic on 10-week-old white grandiflora petunia plants that were inoculated on the roots or on the crown using mycelium fragments, or via soil inoculation using zoospores. A rapid decline was observed after soil inoculations with zoospores. Root fresh weight decreased significantly and the root rot index and severity of foliage symptoms increased significantly (P ≤ 0.05), relative to noninoculated plants after 14 days of incubation. Two isolates (Ph-1 and Ph-2) were pathogenic on bell pepper and one isolate (Ph-1) was pathogenic on tomato after root inoculation. Two isolates (Ph-2 and Ph-3) were pathogenic on the fruit of avocado, bell pepper, cherry tomato, cucumber, kiwifruit, lemon, pear, pepino, and potato tubers, demonstrating the pathogen's ability to cause postharvest infection of fruit of a wide range of host plants. The efficacy of mefenoxam at 0.1 mg/ml mixed with either chlorothalonil at 1.0 mg/ml or mancozeb at 1.6 mg/ml was demonstrated in this study, whereas chlorothalonil and mancozeb alone did not control disease development. No significant differences were obtained between foliage and soil drench applications. This study demonstrated that P. cryptogea is the cause of the rapid decline found on petunia in Santiago, Chile and, to our knowledge, this is the first report giving a detailed description of a disease caused by P. cryptogea on petunia.