![]() Tuber lesions first appear as irregular, dark blotches. See pictures of late blight on stem and leaves. As conditions become moist and cool, disease development resumes. Under continuously wet conditions, the disease progresses rapidly and warm, dry weather will slow or stop disease development. On the leaf underside, a spore-producing zone of white moldy growth approximately 0.1 - 0.2 inches wide may appear at the border of the lesion. Under moist, cool conditions, water-soaked spots rapidly enlarge and a broad yellow halo may be seen surrounding the lesion (Mohan et al., 1996). Late blight will first appear as water-soaked spots, usually at the tips or edges of lower leaves where water or dew tends to collect. A2 may multiply faster than the A1 mating type. Soil survival from season to season may be possible. The A2 mating type can result in oospores which do not need a living host. This would result in a much greater genetic diversity. The concerns about the A2 mating type are that sexual reproduction can now occur between the two types when they are in the same field. But, there have been reports in North America of the appearance of strains that are A2 type (Goodwin and Drenth, 1997). The late blight pathogen (US-1) that has appeared in the past is an A1 type. There is also concern over the appearance of A2 mating types of the pathogen. Some of these new pathogenic strains are also more aggressive and virulent than the old (US-1) strain that affected the world in the 19th century. These mutations, most notably strain US-8, have made the pathogen resistant to control by metalaxyl, the stand-by fungicide for many years. ![]() In the late twentieth century, there have been major re-occurrences and concern around the world over this pathogen and its disease due to recent mutations (Fry and Goodwin, 1997). Late blight was responsible for the Irish potato famine in the mid-nineteenth century (Daly, 1996). ![]() In the free exposition system the highest values of these parameters with 77%, 0.15 and 1,573, respectively, were obtained however, the introductions LA1480 and LA2075 showed the lowest values under this production system.Ĭhromista phylogenetic resources severity solanaceae rate of disease development area under the disease progress curve.Late blight (Phytophthora infestans) fungus is in the same genus as the fungus causing pink rot (P. According to the analysis, under the semi cover system the lowest numerical values for final severity, r and AUDPC, with 47%, 0.09 and 1,133, was obtained, respectively standing out the introductions LA1480, IAC1686, LA2131 and LA2692. Finally, an analysis of variance and Duncan's tests was conducted. In addition, the regression coefficients of the evaluated variables was calculated. The evaluated variables were: severity (%), rate of disease development (r) and area under the disease progress curve (AUDPC) of late blight. Split plots was the experimental design used, being the main plots the production systems, and the subplots, the tomato introductions, with four replications. The study was conducted with fifteen wild tomato introductions at the Montelindo's farm of the Universidad de Caldas, in two production systems: free exposition and semi cover. To reach this purpose, it is necessary to carry out epidemiological studies and evaluate wild introductions against tomato late blight caused by Phytophthora infestans, the most devastating disease worldwide. Hence, it is necessary to evaluate and identify promising wild genotypes to observe their reaction to the main pathological problems of cultivated species, in order to be considered in future programs of tomato production improvement. ![]() Most of the genes responsible of resistance of tomato to fungi, bacteria, virus and nematodes, has been derivate from wild species of tomato. EPIDEMIOLOGY OF LATE BLIGHT ( Phytophthora infestans(MONT.) DE BARY) IN FIFTEEN INTRODUCTIOS OF WILD TOMATO. CARDONA-PIEDRAHITA, Luisa Fernanda CASTANO-ZAPATA, Jairo and CEBALLOS-AGUIRRE, Nelson. ![]()
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