René Torres

Ochratoxigenic Aspergillus species on grapes from Chilean vineyards and Aspergillus threshold levels on grapes.

This study reports the incidence of ochratoxigenic strains of Aspergillus on Chilean grapes (Vitis vinifera) and wineries, and production of OTA levels in wines with grapes having different levels of contamination with OTA-producing Aspergillus carbonarius was studied. A. carbonarius, A. niger, A. niveus, A. paradoxus, A. versicolor, A. wentii, and A. westerdijkiae were identified on apparently healthy clusters of red and white grape cultivars. However, A. carbonarius and A. niger were the most frequently identified species, more abundant on red than white grape cultivars. Aspergillus spp. populations increased between veraison and harvest, but the isolation frequencies were relatively low over the entire growing season. At the winery, A. carbonarius, A. niger and A. westerdijkiae were occasionally found in the air, exclusively during winemaking. OTA-producing strains were only found among isolates of A. carbonarius, A. niger, A. wenti, and A. westerdijkiae, producing 2 to 17 microg/L of OTA in liquid medium; however, A. westerdijkiae produced the highest OTA concentration in vitro. Red wines elaborated with 0.5% of grapes infected with an OTA-producing strain of A. carbonarius (Aspuc-SB36) exceeded the 2 microg/L of OTA tolerance established for wines by the European Community. Therefore, a threshold below 0.5% infected berries is proposed for red wines. ELISA tests proved to be useful for detecting OTA in broth culture as in wine samples.

Pre- and post-infection activity of new fungicides against Botrytis cinérea and other fungi causing decay of table grapes

R.A. Serey, R. Torres, and B.A. Latorre. 2007. Pre- and post-infection activity of new fungicides against Botrytis cinerea and other fungi causing decay of table grapes. Cien. Inv. Agr. 34(3):215-224. Pre- and post-harvest diseases restrict table grape production and exports (Vitis vinifera L.) in Chile, with the most important disease being grey mold (Botrytis cinerea). In addition, rot due to Aspergillus niger, Cladosporium herbarum, Penicillium expansum, and Rhizopus stolonifer frequently occurs. The pre- and post-infection activity of fungicides against r these pathogens was studied on Thompson Seedless table grapes. Detached, mature, berries were used, and inoculations were performed with 20 μL of a 10 6 spores·mL -1 suspension placed on three punctures aseptically made at the calyx end of each berry. Fungicides used (per liter) were boscalid (600 mg), boscalid (200 mg) + pyraclostrobin (100 mg), boscalid (200 mg) + kresoxim methyl (100 mg), cyprodinil (60 mg) + fl udioxonil (40 mg), BAS 600 KBF (100 mg) + metrafenone (150 mg), BAS 600 KBF (200 mg) + boscalid (300 mg), BAS 600 KBF (100 mg) + pyraclostrobin (100 mg), and captan (400 mg). Each fungicide was applied either by drop (12 μL·berry -1 ) placed on three punctures made with a sterile hypodermic needle or by 60 s immersion. Berries were then incubated in humid chambers at 20oC. The pre-infection (protection) activity of the fungicides varied considerably among the pathogens tested and was found to be signifi cant (p < 0.001) and, with one exception (A. niger), it was signifi cantly (p < 0.002) affected by the application method. The interaction between fungicide and application method was only signifi cant (p < 0.001) for R. stolonifer at 48 h post treatment. In general, pre-infection activity gave 0 to 4 days protection after drop applications and 0 to 21 days after immersion treatments. The post-infection (curative) activity varied among pathogens and fungicide treatments. However, it was always below 24 h.

Characterization of Diaporthe australafricana and Diaporthe spp. Associated with Stem Canker of Blueberry in Chile

Stem canker and dieback are important factors that limit the longevity and reduce the yield of blueberry (Vaccinium spp.) in Chile. In this study, species of Diaporthe associated with blueberry were isolated and identified. The internal transcribed spacer (ITS) regions of ribosomal DNA of 30 isolates and the translation elongation factor 1-α (EF1-α) of 14 isolates were sequenced, analyzed, and compared with their morphological and pathological characteristics. The molecular analysis of ITS sequences by alignment with those of ex-type strains deposited in GenBank and morphological characteristics allowed the identification of Diaporthe ambigua, D. australafricana, D. neotheicola, D. passiflorae, and Diaporthe sp. 1. However, morphology alone was insufficient to identify these species. The combined analysis of ITS and EF1-α gene sequences grouped the Chilean blueberry isolates in the same five groups obtained in the ITS analysis. Pathogenicity tests conducted with attached and detached blueberry shoots (<1 year old) and stems (1 to 2 years old) confirmed that isolates of these Diaporthe spp. were pathogenic. The symptoms were reproducible and consisted of necrotic reddish-brown cankers on blueberry shoots and stems. These isolates were capable of infecting blueberry fruit, causing a soft decay, suggesting that they were tissue nonspecific and were also pathogenic on shoots of apple, grapevine, and pear. D. australafricana was the most frequently isolated species and D. ambigua, D. australafricana, and D. passiflorae were highly virulent in shoots, stems, and fruit of blueberry. This study showed that at least four species of Diaporthe are primary pathogens, capable of causing stem canker symptoms on blueberry, and this is the first report of D. ambigua, D. neotheicola, and D. passiflorae attacking this host.

Comparative protein electrophoretic and isoenzymic patterns of Phytophthora cryptogea isolates from chilean kiwifruit and north american deciduous fruits

Isolates of Phytophthora from fruit crops, previously identified as P. cryptogea on the basis of standard morphological criteria, were compared using electrophoretic patterns of total soluble mycelial proteins and isozyme analysis. According to these criteria, all 33 isolates recovered from kiwifruit in Chile were similar or identical to isolates from California recovered from kiwifruit, apple, and cherry. In contrast, the Chilean and California isolates appeared no more related to New York isolates of P. cryptogea than they were to isolates of P cactorum, P cinnamomi, and P megasperma that were similarly examined. Isolates identified as P. cryptogea from deciduous fruit crops in New York appear to belong to a different taxon than isolates of P cryptogea from fruit crops in Chile and California.

Effectiveness of isofetamid, a new succinate dehydrogenase inhibitor fungicide, in the control of grapevine gray mold

El moho gris (Botrytis cinerea) es una enfermedad importante de la vid (Vitis vinifera) en Chile. En los ultimos anos el control se ha basado en la utilizacion de fungicidas de modo de accion especifico lo que conlleva a un alto riesgo de desarrollo de resistencia. Por lo tanto, se necesitan nuevas opciones quimicas para lograr un control satisfactorio de moho gris. Isofetamida es un nuevo fungicida de sitio especifico que actua inhibiendo la respiracion celular. Este fungicida se presenta como una nueva opcion en el control quimico contra el moho gris. El objetivo de este estudio fue determinar la efectividad de isofetamida en el control del moho gris de la vid en Chile. Las pruebas de campo se realizaron en tres vinedos comerciales donde isofetamida demostro tener alta eficacia, similar a fenhexamida, sobre el moho gris. Durante 2012 y 2013, 10 aislamientos se obtuvieron de diferentes vinedos comerciales en el centro de Chile. La concentracion mediana efectiva de isofetamida vario entre 0,3 a 10,0 μg mL-1 y 0,6 a > 10 μg mL-1 para micelio y conidias respectivamente. La eficacia de isofetamida contra B. cinerea vario entre 61.0-100.0% y 37.5-100.0%, en bioensayos de manzanas inoculadas con micelio y conidias respectivamente. Los resultados de este estudio demuestran que isofetamida es un fungicida altamente eficaz contra B. cinerea.

Evaluation of the use of wound-protectant fungicides and biological control agents against stem canker (Neofusicoccum parvum) of blueberry

Economically, blueberry ( Vaccinium corymbosum ) has become a very important fruit crop in Chile, and stem canker ( Neofusicoccum parvum ) has frequently been observed as a major disease. The symptoms are characterized by partial or total death of the foliage associated with extensive reddish-brown canker lesions at the base of the stems. Pruning wounds appear to be the main infection route. In this study, fungicide pastes and biological control agents were evaluated for their effectiveness as pruning wound-protectants against N. parvum . The mycelium of N. parvum was highly sensitive to benomyl, tebuconazole, and iprodione in vitro, with median effective concentrations (EC 50 ) of 0.15-0.25, 0.26-0.33, and 0.52-0.68 µg·mL -1 , respectively. The pastes formulated with 0.1% benomyl, 0.5% tebuconazole, and 0.06% iprodione also provided considerable protection of pruning wounds against N. parvum on the stems of Duke blueberries under field conditions. However, pyraclostrobin, with relatively high EC 50 values (>2 µg·mL -1 ) in vitro, was largely ineffective in vivo at a 0.1% concentration, and 75% citrus extract (Citrus SL), Bacillus subtilis QST713 (Serenade Max), and Trichoderma spp. (Trichonativa) were also ineffective. Additionally, pastes formulated with 5% boric acid, although effective, were phytotoxic. El arandano ( Vaccinium corymbosum ) se ha convertido en un cultivo de fruta economicamente muy importante para Chile. Entre las enfermedades que lo afectan, la cancrosis del tallo ( Neofusicoccum parvum ) ha adquirido gran importancia. Los sintomas se caracterizan por una muerte parcial o total del follaje, asociado a lesiones cancrosas cafe rojizas que afectan externa e internamente en la base de los tallos. Se acepta que la infeccion se inicia a traves de las heridas de poda. Este estudio tuvo como principal objetivo evaluar la eficacia de pastas fungicidas para la proteccion de las heridas contra N. parvum en arandanos. Los resultados obtenidos demostraron que el micelio de N. parvum es muy sensible a los fungicidas benomilo, tebuconazol e iprodione in vitro , con concentraciones medianas efectivas (EC 50 ) de 0,15-0,25; 0,26-0,33 y 0,52-0,68 µg·mL -1 , respectivamente. En condiciones de campo, las pastas fungicidas formuladas con 0,1% de benomilo, 0,5% de tebuconazol o 0,06% de iprodione otorgaron una proteccion considerable de las heridas de poda contra N. parvum en los tallos de arandanos cv. Duke. Pyraclostrobin, con valores de EC 50 > 2 µg mL -1 in vitro , fue relativamente ineficaz in vivo al utilizarlo en una concentracion de 0,1%. Del mismo modo, 75% de extracto citrico (Citrus SL), Bacillus subtilis QST713 (Serenade Max) y Trichoderma spp. (Trichonativa) fueron ineficaces contra N. parvum . Ademas, las pastas formuladas con 5% de acido borico, aunque eficaces, resultaron fitotoxicas.