Publications by T.J. Avis

Ultrastructural alterations in Fusarium sambucinum and Heterobasidion annosum treated with aluminum chloride and sodium metabisulfite.

Wed, 30 Dec 2009

Fingerprinting techniques as tools towards molecular quality control of Pseudozyma flocculosa

Thu, 22 Sep 2005

In an effort to meet the stringent requirements towards registration of microorganisms as biopesticides, several molecular techniques were tested as part of a strategy to develop a quality control system for Pseudozyma flocculosa, the active ingredient of Sporodex, a biofungicide used for the control of powdery mildew fungi. In the first approach, multiplex PCR fingerprints generated by three sets of primers allowed differentiation of several isolates of P. flocculosa from closely related species, or genera such as Tilletiopsis. The same set of primers was used in quality control experiments and revealed fungal contamination that was otherwise not observed by standard culture and microscopy techniques. In addition, the use of random amplified microsatellites generated by (GT)n and (CCA)n primers was applied as a measure of possible genetic variation over 65 repeated subcultures of P. flocculosa. Finally, a novel technique was developed and named reverse intron PCR (RIP), based on the presence of an intron revealed by partial sequencing of mtLSU of P. flocculosa. RIP allowed not only differentiation of P. flocculosa from other species but also separated the isolates of different origins within P. flocculosa. This new technique could find useful applications in phylogenetic studies of closely related fungal species and isolates.

Molecular and physiological analysis of the powdery mildew antagonist Pseudozyma flocculosa and related fungi

Tue, 12 Mar 2002

A number of phenotypic and genotypic characteristics were used to ascertain the identity and diversity of Pseudozyma flocculosa, a natural antagonist of powdery mildews that has received little attention in terms of taxonomy. To this end, several putative isolates of P. flocculosa as well as several closely related species were analyzed. Ribosomal DNA sequences distinguished P. flocculosa from other Pseudozyma spp. and identified two previously unknown Pseudozyma isolates as P. flocculosa. Random amplified microsatellites revealed three distinct P. flocculosa strains among the tested isolates. Biocontrol properties and antifungal metabolite production were limited to the P. flocculosa spp. Results produced useful molecular markers to (i) distinguish P. flocculosa from other related fungi, (ii) identify different strains within this species, and (iii) aid in the construction of isolate-specific molecular tools that will assist in research and development of P. flocculosa as a biocontrol agent of powdery mildew fungi.

Approaches to molecular characterization of fungal biocontrol agents: some case studies

Tue, 12 Mar 2002

An increasing number of fungal biocontrol agents are being developed for control of pests in agriculture and forestry. The use of these living organisms has brought new challenges in research and developement of biocontrol products. Molecular markers provide immense sources of data that can assist scientists in developing tools to monitor the genetic and environmental fate of these agents. Selection of appropriate molecular techniques should be based on the specific characteristics of the organism and on the desired type of information necessary to evaluate a particular step in the developmental process of a biopesticide. Genetic assessment of fungal antagonists is not only desirable but essential to gain insight into the safe and reliable use of biological control products.