M. C. Heath, R. Wood
Mar 1, 1971
Citations
0
Influential Citations
24
Citations
Journal
Annals of Botany
Abstract
The phytoalexin, pisatin, was detected in host tissues 24 h after inoculation of pea leaflets with spores of the leaf-spotting pathogens Ascochyta pisi and Mycosphaerella pinodes. Pisatin continued to accumulate in infected tissue as A. pisi lesions developed and was present in inhibitory concentrations in the brown tissue beyond the region colonized by the pathogen. During the formation of limited M. pinodes lesions, concentrations of pisatin were highest 2 days after inoculation. Levels were more variable and lower in older lesions which appeared to contain no other inhibitors of germ-tube growth. Spreading lesions caused by M. pinodes on leaflets floating on water contained little or no pisatin although little was released to the water below. These lesions did, however, contain other highly active inhibitors of germ-tube growth. The significance of these results in terms of limitation of lesions are discussed. The ease with which M. pinodes lesions can become progressive may reflect the greater ability of this pathogen to grow in high concentrations of pisatin under certain conditions.