Biopesticide activity from drimanic compounds to control tomato pathogens

Indexación: Scopus.Tomato crops can be affected by several infectious diseases produced by bacteria, fungi, and oomycetes. Four phytopathogens are of special concern because of the major economic losses they generate worldwide in tomato production; Clavibacter michiganensis subsp. michiganensis and Pseudomonas syringae pv. tomato, causative agents behind two highly destructive diseases, bacterial canker and bacterial speck, respectively; fungus Fusarium oxysporum f. sp. lycopersici that causes Fusarium Wilt, which strongly affects tomato crops; and finally, Phytophthora spp., which affect both potato and tomato crops. Polygodial (1), drimenol (2), isonordrimenone (3), and nordrimenone (4) were studied against these four phytopathogenic microorganisms. Among them, compound 1, obtained from Drimys winteri Forst, and synthetic compound 4 are shown here to have potent activity. Most promisingly, the results showed that compounds 1 and 4 affect Clavibacter michiganensis growth at minimal inhibitory concentrations (MIC) values of 16 and 32 μg/mL, respectively, and high antimycotic activity against Fusarium oxysporum and Phytophthora spp. with MIC of 64 μg/mL. The results of the present study suggest novel treatment alternatives with drimane compounds against bacterial and fungal plant pathogens. © 2018 by the authors.https://www.mdpi.com/1420-3049/23/8/205

Patogenicidad y susceptibilidad a Phoma exigua Desm. de tres portainjertos y dos variedades de limonero (Citrus lemon L.)

En la localidad de La Serena, IV Región del país, se detectaron plantas de limonero de dos años de edad con síntomas de atizonamiento a nivel de brotes y presencia de cancros en el tronco con abundante exudación de goma, produciendo en algunos casos la muerte de las plantas. A partir de la zona de avance de estas lesiones se aisló en forma consistente micelio correspondiente a Phoma exigua Desm. A partir deaislamientos puros de este hongo se inocularon frutos y plantas de limonero, obteniéndose en estas últimas los mismos síntomas antes descritos. De este ¡nodo se demostró la patogenicidad de la cepa obtenida, la que fue recuperada a partir de las lesiones, manteniéndosela mismas características del cultivo. Se realizaron además pruebas de susceptibilidad de dos variedades de limón crecidas sobre tres portainjertos y la de éstos por separado. Los resultados demostraron que todas las combinaciones fueron afectadas, existiendo diferenciasen susceptibilidad, siendo la variedad Génova más susceptible que la variedad Eureka.Se concluye que esta sintomatología, sería una nueva enfermedad que afecta al cultivo del limón, la que denominamos. "Cancrosis y atizonamiento del limonero ", causada por Phoma exigua Desm

IDENTIFICACION DE Fusarium solani (Mart.) Sacc. COMO AGENTE CAUSAL DE LA PODREDUMBRE DEL PIE DE TOMATE

Se investigó la etiología de una pudrición basal y radical causada por Fusarium sp. en plantas de tomate enfermas en invernaderos fríos de la V Región de Chile. Se identificó como patógeno a Fusarium solani, hongoque ha sido descrito en otros países causando síntomas similares a los observados en este trabajo. Los síntomas en terreno y en las plantas inoculadas fueron: pudrición radical, podredumbre del pie y necrosis vascular

Biological control of Rhizoctonia solani in tomatoes with Trichoderma harzianum mutants

Biocontrol of Rhizoctonia solani in tomatoes cultivated under greenhouse and field conditions was analyzed using the Trichoderma harzianum mutants Th650-NG7, Th11A80.1, Th12A40.1, Th12C40.1 and Th12A10.1 and ThF2-1, respectively. Their innocuousness on tomato cultivars 92.95 and Gondola (greenhouse assays), and on cultivar Fortaleza (field assays) was established. Alginate pellets (1.7 g pellets/L soil) containing c.a1 x 105 colony forming units (cfu)/g pellet were applied to a soil previously inoculated with R. solani at transplant (greenhouse) or to a naturally infected soil (field). Controls considered parental wild strains, a chemical fungicide and no additions. Th11A 80.1, Th12A10.1 and Th650-NG7 prevented the 100% mortality of tomato plants cv. 92.95 caused by R. solani, and the 40% mortality in tomato plants cv. Gondola (greenhouse assays). Mortality reduction was reflected in canker level lessening and in plant parameters increases (development, fresh and dry weights). A different degree of susceptibility of tomato plants was observed, being Gondola cv. more resistant than 92.95 cv. to infection in a soil previously inoculated with R. solani. Tomato plants of cv. Fortaleza did not show mortality in naturally infected soils (field assays), where the mutant ThF2-1 reduced significantly the canker level caused by R. solani

Efecto del Período de Inundación en el Desarrollo de la Tristeza del Palto (Persea americana), Causada por Phytophthora cinnamomi

La tristeza del palto (=aguacate) (Persea americana Mill), causada por Phytophthora cinnamomi Rands ocurre muy a menudo en huertos ubicados en suelos arcillosos y saturados por periodos prolongados. Este trabajo tuvo el propósito de caracterizar e identificar la especie de Phytophthora asociada a la tristeza del palto en Chile y de estudiar el efecto de la saturación (potencial mátrico = 0) del suelo sobre el desarrollo de esta enfermedad. Los aislamientos obtenidos correspondieron a P. cinnamomi, identificándose las razas A1 y A2. Paltos inoculados del cultivar Mexicola, independientemente del manejo del agua del suelo, desarrollaron marchitez, clorosis, necrosis foliar y tuvieron un significativo (p < 0,05) menor crecimiento, inferior número hojas y una reducida superficie foliar respecto de los testigos sin inocular. Los síntomas aéreos estuvieron siempre asociados con la presencia de pudrición parcial o total de las raíces, lo que eventualmente provocó muerte de plantas. Los ciclos de inundación realizados quincenalmente por 12, 24, 48 o 96 h tuvieron un efecto estadísticamente significativo (p <0,001) en el desarrollo de esta enfermedad en paltos del cultivar Mexicola inoculados con P. cinnamomi, los que desarrollaron entre 12,1 y 62,5% de pudrición radical, con relación a plantas igualmente inundadas sin inocular. La relación entre el tiempo de inundación y la incidencia de pudrición radical obtenida por regresión lineal fue igual a Y = 24,5 + 0,89X (R2 = 0,86; p = 0,05) e Y = 2,20 + 0,16X (R2 = 0,66; p = 0,19) en paltos inoculados y sin inocular, respectivamente. De acuerdo con estos resultados repetidos periodos de inundación por 24 h serían suficientes para producir un 50% de pudrición radical. En consecuencia, y a pesar de las limitaciones que pudieran existir para libremente extrapolar estos resultados a las condiciones de campo, es posible concluir que las inundaciones reiteradas y frecuentes del suelo, por periodos iguales o superiores a 24 h, son conductivas a un severo desarrollo de tristeza del palto, causada por P. cinnamomi

Biological control of Rhizoctonia solani in tomatoes with Trichoderma harzianum mutants

Biocontrol of Rhizoctonia solani in tomatoes cultivated under greenhouse and field conditions was analyzed using the Trichoderma harzianum mutants Th650-NG7, Th11A80.1, Th12A40.1, Th12C40.1 and Th12A10.1 and ThF2-1, respectively. Their innocuousness on tomato cultivars 92.95 and Gondola (greenhouse assays), and on cultivar Fortaleza (field assays) was established. Alginate pellets (1.7 g pellets/L soil) containing c.a1 x 105 colony forming units (cfu)/g pellet were applied to a soil previously inoculated with R. solani at transplant (greenhouse) or to a naturally infected soil (field). Controls considered parental wild strains, a chemical fungicide and no additions. Th11A 80.1, Th12A10.1 and Th650-NG7 prevented the 100% mortality of tomato plants cv. 92.95 caused by R. solani, and the 40% mortality in tomato plants cv. Gondola (greenhouse assays). Mortality reduction was reflected in canker level lessening and in plant parameters increases (development, fresh and dry weights). A different degree of susceptibility of tomato plants was observed, being Gondola cv. more resistant than 92.95 cv. to infection in a soil previously inoculated with R. solani. Tomato plants of cv. Fortaleza did not show mortality in naturally infected soils (field assays), where the mutant ThF2-1 reduced significantly the canker level caused by R. solani

Incidence of Citrus tristeza virus in Chile and Biological and Serological Characterization of 100 Isolates

A survey was performed from 1999 to 2002 in the main citrus regions (13,551 ha) of Chile to estimate the Citrus tristeza virus(CTV) incidence. One thousand three hundred and twenty-three commercial citrus orchards were visited and 90,267 trees were observed for symptoms, sampled and analyzed by DAS-ELISA and tissue print-ELISA using 3DF1 and 3CA5 monoclonal antibodies. In this survey stem pitting symptoms were detected on CTV-infected grapefruit and Mexican lime trees grown in small orchards located in the Pica Oasis where the CTV incidence was 17.2%. In central Chile, where the main commercial orchards are located, CTV incidence ranged from zero to 0.37%. The average incidence of CTV in Chile was estimated at 0.38%. From this survey 100 CTV isolates representative of different hosts and geographical origins were selected and inoculated on sweet orange and/or Mexican lime and conserved in a collection kept in screenhouse facilities. The isolates in the collection were biologically and serologically characterized. Severe CTV isolates were found in Region I (where Pica Oasis is located). Serological characterization was done by DASI-ELISA using 12 different monoclonal antibodies, including MCA 13. Eight different serogroups were detected, two of which included CTV isolates which yielded a positive MCA 13 reaction