Sensivity of Jordanian Isolates of Alternaria solani to Manchotane

Early blight of potato, caused by Alternaria solani, poses a significant risk to potato crops worldwide. Fifty A. solani isolates representing a population were collected from the Jordan Valley, purified, and tested for their sensitivity to the fungicide mancothane. The isolates were tested against a series of concentrations of 0, 0.1, 1, 10, 100, and 1000 mg mancothane ml-1 in 5% sodium dodecyl sulfate (SDS). Some A. solani isolates tolerated up to 1000 mg mancothane ml-1. Isolates treated with the various concentrations were divided into 5 groups based on the percentage of A. solani growth achieved despite treatment: group 1 comprised isolates with mycelial growth of 0.1– 20.9%; group 2, 21–40.9%; group 3, 41–60.9%; group 4, 61–80.9%; and group 5, 81–100%. Ninety-seven percent of all isolates grew at 0.1 mg mancothane ml-1, 94% at 1 mg ml-1, 86% at 10 mg ml-1, 66% at 100 mg ml-1, and 16% at 1000 mg ml-1. Isolates appeared to be distributed normally at 10 mg mancothane ml-1. Eight isolates were highly resistant to mancothane and grew even at the highest test concentration. An A. solani population collected from potato fields in the Jordan Valley exhibited a moderate level of resistance to mancothane. Growers should be careful and vigilant when using this fungicide to control early blight

Wild Honey Inhibits Growth od Some Phytopathogenic Fungi <em>in vitro</em>

Wild honey was diluted to 1000 ppm with sterile distilled water and tested in vitro for inhibition of the plant pathogenic fungi Fusarium oxysporum, Rhizoctonia solani, Alternaria solani, Stemphylium solani, Colletotrichum sp., and Phytophthora infestans. Wild honey was effective against all these fungi, particularly A. solani and P. infestans, the causal agents of early and late blight diseases respectively; also against R. solani and F. oxysporum, and to a less extent against S. solani and Colletotrichum sp. This is the first report on the inhibiting effect of wild honey against plant pathogenic fungi

Proteomics analysis suggests broad functional changes in potato leaves triggered by phosphites and a complex indirect mode of action against Phytophthora infestans

Phosphite (salts of phosphorous acid; Phi)-based fungicides are increasingly used in controlling oomycete pathogens, such as the late blight agent Phytophthora infestans. In plants, low amounts of Phi induce pathogen resistance through an indirect mode of action. We used iTRAQ-based quantitative proteomics to investigate the effects of phosphite on potato plants before and after infection with P. infestans. Ninety-three (62 up-regulated and 31 down-regulated) differentially regulated proteins, from a total of 1172 reproducibly identified proteins, were identified in the leaf proteome of Phi-treated potato plants. Four days post-inoculation with P. infestans, 16 of the 31 down-regulated proteins remained down-regulated and 42 of the 62 up-regulated proteins remained up-regulated, including 90% of the defense proteins. This group includes pathogenesis-related, stress-responsive, and detoxification-related proteins. Callose deposition and ultrastructural analyses of leaf tissues after infection were used to complement the proteomics approach. This study represents the first comprehensive proteomics analysis of the indirect mode of action of Phi, demonstrating broad effects on plant defense and plant metabolism. The proteomics data and the microscopy study suggest that Phi triggers a hypersensitive response that is responsible for induced resistance of potato leaves against P. infestans. Biological significance: Phosphie triggers complex functional changes in potato leaves that are responsible for the induced resistance against Phytophthora infestans.This article is part of a Special Issue entitled: Translational Plant Proteomics. \ua9 2013 Elsevier B.V.Peer reviewed: YesNRC publication: Ye