Interactions ofPythium ultimumwith Germinating Resistant or Susceptible Pea Seeds

Publisher Website
Google Scholar
Abstract
Variously treated seeds of the susceptible pea line ''Dark Skin Perfection'' (DSP) and resistant accesssion, PI [plant introduction] 257593, were planted in soil artificially infested with a range of densities of Pythium ultimum oospores. After 10 days, both the proportion of diseased plants and disease severity were measured. The resulting curves representing the proportion of diseased plants or disease severity vs. inoculum density were similarly shaped for the 2 lines regardless of seed condition or soil fungistasis level. The curves differed markedly in position as reflected by ED50 values. The ED50 value for PI 257593 was greatly reduced by damaging the seed coats, whereas that of DSP was only slightly reduced by similar treatment. Aging seeds prior to planting, which reduces seed vigor and increases exudation during germination, reduced the ED50 values of both lines. ED50 values also differed in 2 different soil mixtures that were tested, but the level of resistance of Pl 257593 relative to that of DSP was not altered. In all cases curves plotted for disease severity vs. the proportion of diseased plants were similar in both shape and position. Levels of resistance or susceptibility as determined by disease severity are therefore due to differences in numbers of infections occurring at a given inoculum density; i.e., are relative to the proportion of oospores which successfully infect the host, and not to differences in host-pathogen interactins following infection. Comparison of these data obtained by generation of proportion of diseases plants vs. inoculum density curves suggest that only the oospores in the spermoplane are capable of infecting the host.

This publication has 1 reference indexed in Scilit: