Characterization of Phytophthora nicotianae isolates from tobacco plants (Nicotiana tabacum) in ColombiaThe 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 ìm and non-papillated and intercalary chlamydospores of medium size of 1.02 ìm 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.
Adapting plantlets to ex vitro conditions is a decisive step in the micropropagation process via organogenesis or somatic embryogenesis (ES). The percentage of success in this stage determines the quality of the product, an example of which is found in cocoa plantlets regenerated by ES, which require specific conditions to overcome the stress of the new environment. Considering the quality of the in vitro plantlets largely determines the survival and growth in ex vitro conditions, the effect of two culture media between the embryo maturation stage and the initial stage of conversion to plantlet was evaluated (EM2 - MM6 and EM2 – MF medium), achieving with the latter greater stem height, root length and the number of true leaves. In the final stage of the conversion and growth of the plantlet, the effect of five culture media was evaluated (ENR6, MF, ENR8, EDL, PR), achieving better results in stem height, root length, and the number of true leaves on MF medium. In addition, it was found that the transition of the EM2-MF had a significant development in the presence of the desired pivoting root and fibrous roots. Under nursery conditions, the growth and development of the plantlets was tested through the inoculation of beneficial microorganisms to promote survival. The plantlets that met the minimum morphological parameters for acclimation were planted in a substrate of coconut palm and sand (3:1 v/v) previously selected in the laboratory (BS). The effect of Pseudomonas ACC deaminase (PAACd), Trichoderma asperellum (Ta) and arbuscular mycorrhiza forming fungus (AMF) and different concentrations of phosphorus (PC) (0%, 50% and 100%) in the Hoagland nutrient solution (1:10) was evaluated. First, for CCN5, 62.5% of survival was obtained with PAACd + AMF. Second, the largest leaf size and survival were obtained with PAACd + Ta for CNCh12 and CCN51; likewise, for CNCh13, the best result was obtained with PAACd. Keywords: Cacao, Clonal propagation, Mycorrhiza, Pseudomonas, Trichoderma.
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