Dynamics of QoI sensitivity in Mycosphaerella fijiensis in Costa Rica during 2000 to 2003

From 1997 onward, the strobilurin fungicide azoxystrobin was widely used in the main banana-production zone in Costa Rica against Mycosphaerella fijiensis var. difformis causing black Sigatoka of banana. By 2000, isolates of M. fijiensis with resistance to the quinolene oxidase inhibitor fungicides were common on some farms in the area. The cause was a single point mutation from glycine to alanine in the fungal target protein, cytochrome b gene. An amplification refractory mutation system Scorpion quantitative polymerase chain reaction assay was developed and used to determine the frequency of G 143A allele in samples of M. fijiensis. Two hierarchical surveys of spatial variability, in 2001 and 2002,found no significant variation in frequency on spatial scales <10 in. This allowed the frequency of G143A alleles on a farm to be estimated efficiently by averaging single samples taken at two fixed locations. The frequency of G 143A allele in bulk samples from I I farms throughout Costa Rica was determined at 2-month intervals. There was no direct relationship between the number of spray applications and the frequency of G143A on individual farms. Instead, the frequency converged toward regional averages, presumably due to the large-scale mixing of ascospores dispersed by wind. Using trap plants in an area remote from the main producing area, immigration of resistant ascospores was detected as far as 6 km away both with and against the prevailing wind.

Tycho: a wide-area messaging framework with an integrated virtual registry

In a distributed environment remote entities, usually the producers or consumers of services, need a means to publish their existence so that clients, needing their services, can search and find the appropriate ones that they can then interact with directly. The publication of information is via a registry service, and the interaction is via a high-level messaging service. Typically, separate libraries provide these two services. Tycho is an implementation of a wide-area asynchronous messaging framework with an integrated distributed registry. This will free developers from the need to assemble their applications from a range of potentially diverse middleware offerings, which should simplify and speed application development and more importantly allow developers to concentrate on their own domain of expertise. In the first part of the paper we outline our motivation for producing Tycho and then review a number of registry and messaging systems popular with the Grid community. In the second part of the paper we describe the architecture and implementation of Tycho. In the third part of the paper we present and discuss various performance tests that were undertaken to compare Tycho with alternative similar systems. Finally, we summarise and conclude the paper and outline future work.