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Potato Late Blight (potato + late_blight)
Selected AbstractsPrediction studies supported by computer on potato late blight in central Anatolia in Turkey,EPPO BULLETIN, Issue 2 2007E. Cakir Prediction of potato late blight epidemics, caused by Phytophthora infestans (Mont) de Bary, was studied in three different villages of Bolu Province having large potato growing areas with the Winstel and Ullrich Schrodter models in the years 2002,05. During these years, a late blight outbreak was observed only in 2005 with the disease being less apparent in the other years. The Ullrich Schrodter model was found to poorly predict potato late blight epidemics in 2005. The Winstel model gave first warnings too early but correctly predicted late infections. Both the A1 and A2 mating types were found in Central Anatolia for the first time, in Bolu province. [source] Is there a trade-off between aggressiveness and overwinter survival in Phytophthora infestans?FUNCTIONAL ECOLOGY, Issue 3 2007J. MONTARRY Summary 1Selection during interepidemic stages is crucial for the evolution of pathogen populations. Trade-offs involving aggressiveness (quantitative pathogenicity) have rarely been explored in pathogens with a life cycle requiring the disease-causing organism to change organs within the same host. 2We investigated the existence of a trade-off between aggressiveness and survival in Phytophthora infestans, the pathogen causing potato late blight. In France, P. infestans behaves as an obligate biotroph, surviving in infected tubers. Aggressive isolates, which are favoured during the epidemic, may exhaust their nutrient supply too quickly to bridge seasons, resulting in a possible trade-off between the two life stages. 3We inoculated tubers with isolates possessing different aggressiveness levels, let them overwinter as outdoor piles at three different sites, and scored the proportion of live tubers the following spring. 4At two sites, infection caused early tuber sprouting, which can be seen either as a manipulation of the host by the pathogen, or as an attempt by the host to escape. 5Overwinter survival was higher for control than for inoculated tubers, but did not differ between tubers inoculated with different isolates. This suggests that aggressiveness should gradually increase in P. infestans populations, unless a trade-off occurs at another stage of the life cycle. [source] Reaction of Certain Solanaceous and Asteraceous Plant Species to Inoculation with Phytophthora infestans in CameroonJOURNAL OF PHYTOPATHOLOGY, Issue 6 2004D. A. Fontem Abstract Experiments were conducted to detect potential hosts of Phytophthora infestans, causal agent of potato late blight among weeds occurring in Cameroon. Isolates of P. infestans isolated from garden huckleberry (Solanum scabrum), potato (S. tuberosum) and tomato (S. lycopersicon) were inoculated on detached leaves of 12 solanaceous and 14 asteraceous species collected from the potato agroecosystem in the western highlands of Cameroon. Isolates of P. infestans from huckleberry and potato infected the same host plants as well as gboma eggplant (S. macrocarpon) and two asteraceous weeds; Billy goatweed (Ageratum conyzoides) and Dichrocephala (Dichrocephala integrifolia). Inoculum from potato caused late blight symptoms on haemorrhage plant (Aspilia africana); while inoculum from tomato resulted in late blight on worowo (Solanecio biafrae). This is the first report of late blight infection on S. macrocarpon, A. conyzoides, Sol. biafrae and Asp. africana in Cameroon. The research results indicate that some asteraceous and solanaceous weeds may be alternative hosts of P. infestans in the potato agroecosystem. [source] Investigating the role of ABC transporters in multifungicide insensitivity in Phytophthora infestansMOLECULAR PLANT PATHOLOGY, Issue 1 2006HOWARD S. JUDELSON SUMMARY Isolates of the oomycete Phytophthora infestans exhibit a wide range of intrinsic sensitivities to fungicides, which potentially influences the application rates of chemicals needed to control potato late blight. To help understand what determines such levels of sensitivity, a genetic approach was employed which followed the segregation of sensitivities to structurally diverse fungicides such as metalaxyl and trifloxystrobin. Progeny exhibited broad distributions of sensitivity phenotypes, consistent with the behaviour of a quantitative trait. Measurements of the inhibition of strains by seven fungicides revealed that basal sensitivities to metalaxyl and trifloxystrobin, and to cymoxanil and dimethomorph, correlated at the 95% confidence level. These compounds have distinct modes of action, suggesting the involvement of a multifungicide efflux phenomenon mediated by ABC transporters. To determine whether such proteins contribute to variation in sensitivity, 41 full transporters and 13 half transporters were identified from P. infestans and their mRNA levels compared in strains exhibiting higher or lower sensitivities to fungicides. No correlation was observed between the expression of any ABC transporter and fungicide sensitivity. Other genes, or variation in the activities of the transporters, may therefore explain the differences between strains. Five ABC transporters were induced by several fungicides in strains with both higher and lower sensitivities to fungicides, which probably reflects the existence of a network for protecting against natural and artificial toxins. [source] Comparison of three diagrammatic keys for the quantification of late blight in tomato leavesPLANT PATHOLOGY, Issue 6 2009F. M. Corrêa Three diagrammatic grading keys were designed for the assessment of the severity of late blight (caused by Phytophthora infestans) in tomato leaves. Simplified and broad keys considered, respectively, six (3, 12, 22, 40, 60 and 77%) and eight (3, 6, 12, 22, 40, 60, 77 and 90%) levels of disease severity, whilst a modified key based on a previous proposal for potato late blight considered six levels (1, 5, 10, 16, 32 and 50%). The keys were validated by 24 evaluators who assessed digital images of tomato leaves exhibiting different areas with lesions. Evaluator errors were compared using a mixed model in which evaluators were considered as random effects and the keys and evaluations as fixed effects. The accuracy and precision of the evaluators were compared by simple linear regression between the estimated and actual values of disease severity. The repeatability of evaluators was assessed using Pearson's correlation coefficient. There was significant (P , 0·001) variability amongst the errors made by evaluators, although the precision of each of the three keys was high with a coefficient of determination (R2) of 0·96, 0·93 and 0·83 for the simplified, broad and modified key, respectively. Repeatability of estimations amongst the evaluators was adequate (correlation coefficients of 0·91, 0·91 and 0·90 for the three keys, respectively). The simplified and broad keys resulted in higher precision and accuracy for the estimation of severity than did the modified key. Since the simplified key considers a smaller number of disease severity levels, its use is recommended in the assessment of late blight in tomato leaves. [source] Efficacy of the R2 resistance gene as a component for the durable management of potato late blight in FrancePLANT PATHOLOGY, Issue 6 2005F. Pilet Many race-specific resistance genes to potato late blight are overcome in France, but the disease appears later on genotypes carrying the R2 gene. This study examined whether R2 could contribute to durable late-blight control in France, and analysed the conditions of its performance. Plants grown from tubers of different physiological ages showed no difference in R2 expression in field and climate-chamber experiments, demonstrating that the delay in epidemic onset provided by R2 was not the result of gene inactivation in old plants. Among isolates collected at one site, those virulent on R2 were classified into three AFLP profiles. AFLP-VII comprised exclusively isolates virulent to R2, whereas AFLP-IV and AFLP-V included both virulent and avirulent isolates. No significant aggressiveness differences were observed between virulent and avirulent isolates from AFLP-V; however, isolates from AFLP-VII were significantly less aggressive than virulent isolates from AFLP-V. These results indicate that: (i) the delayed onset of epidemics on R2 cultivars is the result of the breakdown of R2 by virulent isolates; (ii) aggressiveness of isolates virulent to R2 depends primarily on the genetic background of the pathogen where the mutation to virulence occurs; and (iii) this mutation does not lead per se to lower pathogenic fitness. It is suggested that R2 is unlikely to make a lasting contribution to late-blight control in France, and that diversification strategies such as cultivar mixtures might not considerably increase its durability. [source] | ||||||||||