In Vitro Variability Among Isolates of EightPhytophthoraSpecies in Response to Phosphorous Acid

Publisher Website
Google Scholar
Abstract
The ED50 values for inhibition of mycelial growth in vitro by phosphorous acid (H3PO3) ranged 5.2-224.4 .mu.g/ml for 9 Phytophthora spp. Among the most sensitive species were P. citricolu, P. citrophthora and P. cinnamomi. One of the most tolerant species was P. megasperma f. sp. medicaginis. At the extreme of the range, P. infestans from potato had an ED50 value of 224.4 .mu.g/ml. Even among a group of similarly sensitive isolates, it was possible to differentiate them at a species level in terms of their growth response to H3PO3. Isolates of P. citricola from avocado were inhibited by 48.3-67.6%, and those of the A2 mating type of P. cinnamomi by 11.3-38.5%, in the presence of 5 .mu.g/ml H3PO3. Isolates of P. citrophthora from citrus were inhibited 80.3-89.3%, compared with 27.9-58.8% for isolates of P. parasitica in the presence of 10 .mu.g/ml H3PO3. [Other species studied were P. palmivora, P. capsici, P. boehmeriae and P. cactorum.].