![Sample our Environment & Agriculture journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5934/TOC-Subject-Sample-2021-Environment-Agriculture.jpg"})
Abstract
The effect of added calcium on the developmental fate of encysted zoospores was studied in four strains of Phytophthora sojae. Cysts from all strains were capable of producing both secondary zoospores or hyphal germlings following vortex-induced encystment. In three of the four strains the majority of the cysts released a secondary zoospore in lieu of producing a hyphal germling. High, but not low levels of external calcium were effective in increasing the percentage of cysts that germinated and suppressing the percentage of cysts that released a secondary zoospore in all strains. Addition of the host-specific chemoattractant, genistein to encysted zoospores did not suppress the development or release of secondary zoospores. These results demonstrate that the developmental switch from zoospore re-emergence to cyst germination is dependent upon calcium availability. Since the addition of calcium was also effective in stimulating direct germination of zoospores in develoPl.ng sporangia, calcium supplementation of soils may reduce disease by preventing release of zoospores, thus restricting the spread of infective propagules.
Key Words: