Phytophthora Spp Research Articles

Starch utilization by Phytophthora spp.

Phytophthora spp. were grown on artificial starch agar medium. In some cases, the capacity of starch utilization could be a useful tool in species separation ofPhytophthora. Based on the ability to hydrolyse starch,P. palmivora andP. parasitica could be readily distinguished, whereasP. parasitica andP. parasitica var.nicotianae, P. megasperma andP. megasperma var.sojae (P. sojae) behaved similarly. Starch hydrolysis was indicated by a clear unstained zone within the fungal colony when treated with iodine solution. Simple quantitative analysis of starch hydrolysis was made feasible by the following formula:

Effects of Oxygen and Carbon Dioxide Tensions on Sporangium and Oospore Formation by Phytophthora spp.

Effects of Oxygen and Carbon Dioxide Tensions on Sporangium and Oospore Formation by Phytophthora spp.

Applications of the vital fluorescent labeling technique with brighteners to studies of saprophytic behavior of Phytophthora in soil

The fluorescent brightener, ‘Calcofluor White M2R New’ [disodium salt of 4,4'-bis (4-anilino-6-diethylamino- s-triazin-2-ylamino)-2,2'-stilbene-disulfonic acid] at 100–300 ppm was effective as a vital stain in labeling mycelia and various spore forms of Phytophthora spp. Labeling was achieved by growing the fungus in a liquid medium containing the brightener or by direct staining of fungal propagules before use. The brightener was readily absorbed by the fungus and was non-toxic at the concentrations used. Saprophytic behavior of p. parasitica in soil was studied by introducing labeled propagules directly into soil and recovering them periodically for observation using a soil-smear technique. Under the fluorescence microscope the labeled propagules and subsequently formed germ tubes, mycelia, chlamydospores, sporangia, and encysted zoospores all fluoresced with little interference from the soil mass or soil microflora. Spore germination, mycelial growth, sporulation, and lysis of P. parasitica in non-amended and amended natural soils have been studied with this labeling technique. Labeling was successful also with several other soil fungi.

Experimental Attempts to Transmit Citrus Viruses through Phytophthora spp.

Experimental Attempts to Transmit Citrus Viruses through Phytophthora spp.

Pythiaceous fungi and plant-parasitic nematodes in California pear orchards: I. Occurrence and pathogenicity of pythiaceous fungi in orchard soils

Pythiaceous Fungi and Plant-Parasitic Nematodes in California Pear Orchards I. During a year’s survey of 126 California pear orchards with varying degrees of pear-decline damage, a total of 3,586 isolates of soil-borne fungi of the genera Phytophthora and Pythium were recovered, and, where possible, identified as to species. A direct relationship was found between the severity of pear-decline damage in an orchard and the percentage of isolates from the orchard that were Pythium spp.; and a corresponding inverse relationship between pear-decline damage severity and the percentage of isolates that were Phytophthora spp. Isolates of Phytophthora cactorum and P. cryptogea were found to be pathogenic on Pyrus communis L. hort. var. Winter Nelis and Pyrus serotina Rehd. seedlings. These pathogens were found infrequently, and it was concluded that pythiaceous fungi were not the primary cause of pear decline. Pear fruit and pear and apple seedlings trapped more Pythium spp. than the fruit of apple, lemon, and avocado, while few Phytophthora spp. were trapped in seedlings. Phytophthora spp. isolates were trapped most often in pear and apple fruit. Lemon and avocado fruit yielded a fair number of both genera.