Occurrence and characterization of Alternaria species associated with leaf spot disease in rapeseed in Serbia

The global demand for rapeseed makes it one of the fastest growing markets in crop production, with a need for increasing growing area and productivity, both of which depend on effective pathogen control strategies. Alternaria pathogens cause serious losses of brassica crops and occur in most rapeseed-growing regions around the world. In this study, morphological, molecular, and pathogenic analyses of 113 isolates collected from nine important rapeseed-growing areas in Serbia identified four pathogens: Alternaria brassicae, A. brassicicola, A. japonica, and A. alternata, causing leaf spot disease. Molecular analyses of ITS, GAPDH, Alt a1, and ATP sequences revealed one multilocus haplotype for A. brassicae and A. japonica isolates, whereas for A. brassicicola and A. alternata three and five haplotypes were distinguished, respectively. Pathogenicity tests showed that A. brassicicola was the most virulent while A. brassicae and A. japonica exhibited the same level of pathogenicity. The A. alternata population was generally weakly pathogenic with one nonpathogenic, genetically separated but closely related group of isolates, suggesting that pathogenicity is more unstable in this phylogenetic lineage. The data recorded on rate of growth and sporulation of isolates at 0, 5, 10, 15, 20, 25, 30, 35, and 40 °C revealed significant differences in evolutionary strategies among species, as A. alternata had the widest optimum range and the fastest growth rate, A. brassicicola showed the highest sporulation intensity, and A. brassicae expressed lower optimum temperatures for sporulation compared to other groups. All species indicated the potential for cross-infection of cabbage, and some haplotypes of A. brassicicola were previously isolated from horseradish in Serbia, suggesting the presence of one persistent Alternaria population on multiple brassica hosts in the region. This report describes the first detailed study of Alternaria spp. in rapeseed in Serbia

Antioxidant properties of some lichen species

Antioxidant activity of the acetone, methanol and aqueous extracts of the lichens Cladonia furcata, Hypogymnia physodes, Lasallia pustulata, Parmelia caperata and Parmelia sulcata has been screened in vitro by using different methods (DPPH radical scavenging, superoxide anion radical scavenging, reducing power, determination of total phenolic compounds and determination of total flavonoid ontent). Of the lichens tested, Lasallia pustulata had powerful antioxidant activities. Acetone, methanol and aqueous extracts of this lichen showed 90.93, 69.87 and 65.08% DPPH radical scavenging activities. Moreover, the tested extracts had effective reducing power and superoxide anion radical scavenging. Those various antioxidant activities were compared to standard antioxidants such as ascorbic acid, butylated hydroxyanisole (BHA) and ?-tocopherol. In addition, total content of phenol and flavonoid in extracts were determined as pyrocatechol equivalent, and as rutin equivalent, respectively. The strong relationships between total phenolic and flavonoid contents and the antioxidative activities of tested extracts suggest that these compounds play important role in antioxidant activity. The present stady shows that tested lichen species demonstrated a strong antioxidant activity and can be considered as good sources of natural antioxidants. © 2010 Association of Food Scientists & Technologists (India)

Characterization of Alternaria Species Associated with Leaf Spot Disease of Armoracia rusticana in Serbia

Leaf spot diseases caused by Alternaria species have been reported worldwide in plants in the Brassicaceae family. However, there is little information on Alternaria species causing diseases in horseradish. In the present study, 89 Alternaria spp. isolates from Armoracia rusticana, sampled from nine districts in Serbia, were characterized based on their morphology, physiology, and molecular markers. Morphological characterization and molecular analyses based on ITS, GAPDH, Alt a 1, and PM-ATP sequences identified three distinct species associated with the disease: Alternaria brassicae, A. brassicicola, and A. alternata. For all species, growth and sporulation rates at 0, 5, 10, 15, 20, 25, 30, 35, and 40°C showed a quadratic response, with A. alternata having the widest temperature optimum (20 to 30°C) while A. brassicicola had higher optimum temperatures (20 to 25°C) than A. brassicae (15 to 20°C). To gain a better understanding of the pathogenicity of these species, the influence of leaf age, host susceptibility, and ability to infect artificially wounded and nonwounded leaves were tested. The pathogenicity test identified A. brassicicola and A. brassicae as the main causal agents of horseradish leaf spot disease. Results indicated that young and intact leaves of horseradish and cabbage were less susceptible to infection and also suggested the potential for cross-infection between these two hosts. Haplotype networks showed haplotype uniformity for A. brassicae, two haplotype groups of A. brassicicola, and eight haplotype groups of A. alternata in Serbia and suggest the possible association of some haplotypes with the geographic area. This study is the first to investigate Alternaria leaf spot disease on A. rusticana in Serbia and is the first record of A. brassicicola on horseradish in this country