Resumen del Libro
Natural infection of American soybean rust, caused by Phakopsora meibomiae Arthur, was studied during 2006 to 2008 in experimental plots established at Isabela, Adjuntas and Juana Diaz Agriculture Experiment Stations of the University of Puerto Rico. The American soybean rust was observed on Lablab purpureus and Phaseolus lunatus in Adjuntas from June to October, 2007. Soybean rust identification was carried out by DNA analysis using PCR of the ITS region of the rDNA. In order to observe natural infections on wild hosts, different surveys were conducted in fourteen municipalities of the island. Twenty nine percent of the samples were positive for P. meibomiae. L. purpureus presented the highest disease severity. Additionally, P. meibomaie was found in Vigna luteola, Macroptilium lathyroides, Pachyrhizus erosus, P. lunatus and Vigna sp. Thirty eight percent of infected legumes were observed between 501 and 600 meters. Two different rust lesions were observed: a tan color reaction with abundant sporulation, and a reddish brown lesion with reduced sporulation. Lesion size on L. purpureus varied from 0.92–0.60 to 0.68–0.41 mm. Average number of uredinium per cm2 was 31.6, with an average of 118.77 urediniospores/uredinium. Uredinium patterns and the release of the urediniospores were observed in scanning electron microscopy. Aditionally, host range studies were conducted in 15 legumes. Canavalia gladiata, Crotalaria brevidens, Mucuna pruriens and Pueraria phaseoloides had immune reaction. The shortest incubation and latent periods were observed on P. vulgaris with 3.23 and 6.27 days, respectively. The greatest number of uredinium per individual lesion was observed on P. vulgaris with an average of 5.79. During the two years of survey, the presence of Asian soybean rust caused by P. pachyrhizi, was never observed nor identified.