Abstract
The black shank disease caused by Phytophthora nicotianae causes losses in tobacco crops up 100%. In Colombia, P. nicotianae populations are poorly known causing wrong diagnostics and erratic management. Amplification of the Ypt1 gene and morphological characteristics of colonies, sporangia, chlamydospores and hyphae were used to identify P. nicotianae isolates. Races were identified according to the reaction induced by each isolate on the differential tobacco varieties Hicks, L8, KY 14 x L8 and NC 1071. As results, 71 isolates of P. nicotianae were identified and classified by races. Colonies of P. nicotianae were of white color, cottony and fluffy texture with smooth, non-swollen hyphae; spherical papillae with an average of 1.26 μm and non-papillated and intercalary chlamydospores of medium size of 1.02 μm that are typical characteristics of P. nicotianae. A species-specific PCR-amplified band of 389 bp was detected in all isolates tested. The presence of races 0, 1 and 3 of P. nicotianae were determined in the Colombian departments of Huila and Santander. To the best of our knowledge, this is the first report of physiological races 0, 1 and 3 of P. nicotianae in Colombia. Results are of relevance for disease management and tobacco breeding.
Highlights
The black shank disease of tobacco is caused by the oomycete plant pathogen Phytophthora nicotianae van Breda de Haan
Black shank disease develops faster under high temperature and humidity, conditions which are frequent in the growing areas of the departments of Huila and Santander where 66% of tobacco is produced in Colombia
ELISA test results were positive for Phytophthora spp. in all isolates tested
Summary
The black shank disease of tobacco is caused by the oomycete plant pathogen Phytophthora nicotianae van Breda de Haan. This disease is the most limiting phytosanitary problem in more than 120 countries where tobacco is grown including Colombia (Abad, 2008; Panabières et al, 2016; Gallup et al, 2018). Black shank disease develops faster under high temperature and humidity, conditions which are frequent in the growing areas of the departments of Huila and Santander where 66% of tobacco is produced in Colombia. Losses may reach 100% under favourable conditions for pathogen development, even with cultivars reported as highly resistant to P. nicotianae as was observed in Colombia in the Department of Huila with cv. K346 (Wilkinson et al, 2003)
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