Detection of airborne sporangia of Pseudoperonospora cubensis and P. humuli in Michigan using Burkard spore traps coupled to qPCR

Cucurbit downy mildew (CDM), caused by the oomycete pathogen Pseudoperonospora cubensis, is a devastating foliar disease on cucumber resulting in reduced yields. In 2004, the pathogen re-emerged in the U.S., infecting historically resistant cucumber cultivars and requiring the adoption of an intensive fungicide program. The pathogen cannot overwinter in Michigan fields but due to an influx of airborne sporangia cucurbit downy mildew occurs annually. In Michigan, spore traps are used to monitor the presence of airborne P. cubensis sporangia in cucumber growing regions to guide the initiation of a fungicide program. However, Pseudoperonospora humuli sporangia, the causal agent of downy mildew on hop, are morphologically indistinguishable from P. cubensis sporangia. This morphological similarity reduces the ability to accurately detect P. cubensis from spore trap samples when examined with the aid of light microscopy. To improve P. cubensis detection, we adapted a qPCR-based assay to allow the differentiation between P. cubensis and P. humuli on Burkard spore trap samples collected in the field. Specifically, we evaluated the specificity and sensitivity of P. cubensis detection on Burkard spore trap tapes using a morphological based and qPCR-based identification assay and determined whether sporangia of P. cubensis and P. humuli on Burkard samples could be distinguished using qPCR. We found that the qPCR assay was able to detect a single sporangium of each species on spore trap samples collected in the field with Cq values below 35.5. The qPCR assay also allowed the detection of P. cubensis and P. humuli in samples containing sporangia from both species. However, the number of sporangia quantified using light microscopy explained only 54% and 10% of the variation in the Cq values of P. cubensis and P. humuli, respectively, suggesting a limited capacity of the qPCR assay for the absolute quantification of sporangia in field samples. After two years of monitoring using Burkard spore traps coupled with the qPCR in cucumber fields, P. humuli sporangia were detected more frequently than P. cubensis early in the growing season (May and June). P. cubensis sporangia were detected approximately 5 -10 days before cucurbit downy mildew symptoms were first observed in cucumber fields during both years. This research describes an improved sporangial detection system that is key for the monitoring and management of P. cubensis in Michigan.

SENSIBILIZACIÓN Y EXPOSICIÓN A PÓLENES Y ESPORAS DE HONGOS ALERGÉNICOS AEROTRANSPORTADOS EN CIUDADES DEL SUR DE PERÚ

Introducción y objetivos: Es muy importante el conocimiento de las fluctuaciones estacionales y anuales sobre los pólenes y esporas de hongos alergénicos aerotransportados en cualquier área geográfica. Nuestro objetivo fue identificar los aeroalérgenos más importantes en la atmósfera de la ciudad urbana de Tacna a los cuales la población está expuesta y desarrollar un estudio alergológico para establecer perfiles de sensibilización en las ciudades de Tacna y Arequipa. Material y métodos: El conteo polínico y fúngico se realizó de acuerdo a la técnica estandarizada con un equipo Burkard spore trap for 7 days (Burkard manufacturing ®, Herst, United Kingdom) y el procedimiento de análisis recomendado por el comité de aerobiología de la Sociedad Española de Alergología e Inmunología Clínica. El estudio alergológico consistió en anamnesis y pruebas cutáneas con extractos (ALK-abello®, Madrid-España). Resultados: Los 3 tipos de esporas de hongos más relevantes que se encontraron durante el periodo de muestreo en orden de abundancia fueron: Cladosporium herbarum (47,22%), Alternaria alternata (33%). Nigrospora spp (19,8%). También encontramos 4 taxones polínicos: Oleacea (94,1%), Chenopodiaceae-Amaranthaceae (3%), Poaceae (2,08%), Myrtaceoe (Eucalipto)(0,77%). Perfil de sensibilización al polen de Olea europea, en muestras aleatorias en las ciudades de Tacna (40%) y Arequipa (36%) y a Alternaria alternata (4%) y (8%) respectivamente. Conclusiones: Éste es el primer estudio realizado en Perú sobre sensibilización y concentraciones de granos de polen y esporas de hongos medidos por método volumétrico. Sugerimos ampliar estudios e implementar estaciones de aerobiología que provean mayor información y sirvan como guía para una mejor prevención, diagnóstico y tratamiento para la población de la zona sur de Perú con enfermedades alérgicas.

Splash dispersal of Botryosphaeriaceae species in Marlborough vineyards

Botryosphaeriaceae species cause dieback and canker in many woody hosts including grapevines with infection occurring when conidia are released during rainfall and splash borne to pruning and trimming wounds This study monitored dispersal of naturally released conidia of Botryosphaeriaceae species in three Marlborough vineyards with a Burkard spore trap and rain water traps Microscopic examination of the Burkard tape and trapped rain water confirmed the presence of Neofusicoccum and Diplodia spp Species were identified on tape and in rainwater with single stranded conformational polymorphism as N luteum N parvum/Nribis N australe D mutila and D seriata To determine conidium dispersal distances sporulating shoot lesions of N parvum isolate B2141 for which an isolate specific marker was developed were placed in one Marlborough vineyard before forecast rainfall periods The rainwater traps were set up around the sporulating lesions at 05 to 20 m in the direction of the prevailing wind and 05 to 5 m in three other directions After 2 days rain Neofusicoccum sp conidia were identified in the collected rainwater by microscope and with the isolate specific PCRRFLP (restriction fragment length polymorphism) for N parvum B2141 This isolate dispersed up to 10 m in the wind direction and up to 1 m in the other three directions

Ascospore dispersal of Venturia inaequalis and subsequent development of scab symptoms in a Hungarian organic apple orchard

In this study, we aimed to study ascospore dispersal of Venturia inaequalis and subsequent disease development in an organic apple orchard (Eperjeske) in 2012 and 2013 on apple cultiva ’Mutsu). Burkard spore trap in March and April were used to monitior ascospore concentration and number of scab symptoms were assesed 20 May in both years. Three peaks were detected in ascospore dispersal in the period of examination which was clearly related to the Mills infection periods. On the basis of the incubation period’s length in April (15–18 days), the appearance of first symptoms had direct connection with the peak of the ascospore discharge. The largest number of symptoms were observed on those parts of the orchards where where the inoculum sources were accumulated.