Novel species of Gliocladiopsis (Nectriaceae, Hypocreales, Ascomycota) from avocado roots (Persea americana) in Australia

Root rot of avocado (Persea americana) is an important disease in seedling nurseries as well as in the field in eastern and southern Australia. During an investigation into the causal organisms of avocado root rot, 19 isolates of Gliocladiopsis were obtained from necrotic lesions on avocado roots and examined by morphology and comparison of DNA sequences from three gene loci (the internal transcribed spacer region of the nuclear rDNA, Histone H3 and β-tubulin). Three new species of Gliocladiopsis are described as a result of phylogenetic analysis of these data. One of the new species, G. peggii, formed a monophyletic group that may represent an unresolved species complex as it contained a polytomy that included a well-supported clade comprising two subclades. Gliocladiopsis peggii is sister to G. mexicana, which is known from soil in Mexico. The remaining two new species, G. whileyi and G. forsbergii, formed a clade sister to G. curvata, which is known from Ecuador, Indonesia and New Zealand

Efficacy of acibenzolar-S-methyl (Bion®) treatment of Australian commercial passionfruit, Passiflora edulis f. sp. flavicarpa, on resistance to Passionfruit woodiness virus (PWV) and activities of chitinase & β-1,3-glucanase

This greenhouse study investigated the efficacy of acibenzolar-S-methyl (Bion®) treatment of lower leaves of passionfruit, (Passiflora edulis f. sp. flavicarpa), on Passionfruit woodiness disease and activities of two pathogenesis-related proteins, chitinase and β-1,3-glucanase after inoculation with passionfruit woodiness virus (PWV). All Bion® concentrations reduced disease symptoms, but the concentration of 0.025 g active ingredient (a.i.)/l was the most effective, reducing disease severity in systemic leaves by 23, 29 and 30 compared with water-treated controls at 30, 40 and 50 days post inoculation (dpi) with PWV, respectively. Correspondingly, relative virus concentration as determined by DAS-ELISA in the upper, untreated leaves (new growth) above the site of inoculation at 50 dpi was reduced by 17 and 22 in plants treated with 0.025 and 0.05 g a.i./l, respectively. Bion® treatment and subsequent inoculation with PWV increased chitinase and β-1,3-glucanase activities in the new leaves above the site of inoculation at 30 dpi with PWV. It was concluded that optimal protective Bion® treatment concentrations were 0.025 and 0.05 g a.i./l

Novel species of Gliocladiopsis (Nectriaceae, Hypocreales, Ascomycota) from avocado roots (Persea americana) in Australia

Root rot of avocado (Persea americana) is an important disease in seedling nurseries as well as in the field in eastern and southern Australia. During an investigation into the causal organisms of avocado root rot, 19 isolates of Gliocladiopsis were obtained from necrotic lesions on avocado roots and examined by morphology and comparison of DNA sequences from three gene loci (the internal transcribed spacer region of the nuclear rDNA, Histone H3 and β-tubulin). Three new species of Gliocladiopsis are described as a result of phylogenetic analysis of these data. One of the new species, G. peggii, formed a monophyletic group that may represent an unresolved species complex as it contained a polytomy that included a well-supported clade comprising two subclades. Gliocladiopsis peggii is sister to G. mexicana, which is known from soil in Mexico. The remaining two new species, G. whileyi and G. forsbergii, formed a clade sister to G. curvata, which is known from Ecuador, Indonesia and New Zealand

Adaptation of a filter paper method for RNA template preparation for the detection of avocado sunblotch viroid by reverse transcription qPCR

An easy, rapid and inexpensive method of preparing RNA template for a reverse transcription qPCR assay for avocado sunblotch viroid (ASBVd) is described. This method depends on the principle of reversible binding of viroid RNA to filter paper under different concentrations of monovalent cation. Lysis buffers containing either sodium or lithium chloride were compared, and 1.5 M lithium chloride was shown to be optimal for the adsorption of the viroid RNA to the filter paper. The extraction method was validated using field samples and equivalent yields of viroid RNA were obtained using this method and either a commercial RNA extraction kit or a dsRNA chromatography method. The filter paper method of RNA extraction is ideally suited for the large-scale surveillance for ASBVd

Current status of the Botryosphaeriaceae in Australia

The Botryosphaeriales, and in particular the Botryosphaeriaceae, are a well-studied group of fungi best known for the canker diseases they cause on woody hosts especially in stressed or damaged trees. Australian Plant Pathology herbaria contain many records for this group, but due to considerable taxonomic changes over the past decade, many of the species names have since been reclassified. In this article we used all published records with available sequence data of the Botryosphaeriaceae in Australia to examine the distribution and host range of these taxa. There are 24 genera encompassing 222 species in the Botryosphaeriaceae; 9 genera and 62 species have been recorded in Australia. Some genera such as Neoscytalidium are only found in warm, humid climates while Dothiorella species are more common in temperate climates. There were species, such as Lasiodiplodia theobromae, Neofusicoccum parvum and Botryosphaeria dothidea, which had a wide host range with many records. However, there were also several species found only in one location on a single host. While systematic data collection is still required, the information presented here provides a baseline of species present in Australia and will underpin future studies into this group of important pathogens