Identification of pathotypes of the sorghum rust pathogen, Puccinia purpurea, in Australia

This study aimed to determine if pathotypic diversity of the sorghum rust pathogen, P. purpurea, exists in eastern Australia. A differential set of 10 Sorghum bicolor genotypes was used to identify four putative pathotypes from the 28 P. purpurea isolates that were tested. Pathotypes 1 and 3 were the most common, together comprising 85.7 % of the isolates tested, while pathotype 2 comprised 10.7 % of isolates, and pathotype 4 the remainder. Based on the limited number of isolates that were tested, there was evidence of geographic specialization amongst the pathotypes, with pathotype 1 not being found in north Queensland. This work has provided conclusive evidence that pathotypes of P. purpurea exist in the sorghum growing regions of Australia and has resulted in the development of a protocol for identifying pathotypes and screening breeding and experimental lines for resistance to these pathotypes. However, further investigations on the pathotypic diversity of P. purpurea and on the temporal and geographic distribution of these four as well as any additional undiscovered pathotypes are needed.

Yield losses in grain sorghum due to rust infection

Although rust (caused by Puccinia purpurea) is a common disease in Australian grain sorghum crops, particularly late in the growing season (April onwards), its potential to reduce yield has not been quantified. Field trials were conducted in Queensland between 2003 and 2005 to evaluate the effect of sorghum rust on grain yield of two susceptible sorghum hybrids (Tx610 and Pride). Rust was managed from 28-35 days after sowing until physiological maturity by applying oxycarboxin (1 kg active ingredient/100 L of water/ha) every 10 days. When data were combined for the hybrids, yield losses ranged from 13.1% in 2005 to 3.2% in 2003 but differences in yield the between sprayed and unsprayed treatments were statistically significant (P a parts per thousand currency signaEuro parts per thousand 0.05) only in 2005. Final area under the disease progress curve (AUDPC) values reflected the yield losses in each year. The higher yield loss in 2005 can be attributed primarily to the early development of the rust epidemic and the higher inoculum levels in spreader plots at the time of planting of the trials.

Molecular phylogenetic analysis reveals six new species of Diaporthe from Australia

Six new species of Diaporthe, D. beilharziae on Indigofera australis, D. fraxini-angustifoliae on Fraxinus angustifolia subsp. oxycarpa, D. litchicola on Litchi chinensis, D. nothofagi on Nothofagus cunninghamii, D. pascoei on Persea americana and D. salicicola on Salix purpurea from Australia are described and illustrated based on morphological characteristics and molecular analyses. Three of the new species no longer produced sporulating structures in culture and two of these were morphologically described from voucher specimens. Phylogenetic relationships of the new species with other Diaporthe species are revealed by DNA sequence analyses based on the internal transcribed spacer (ITS) region, and partial regions of the β-tubulin (BT) and translation elongation factor 1-alpha (TEF). © 2013 Mushroom Research Foundation.