Canadian Forest Service Publications
Production and germination of appressoria in pythium irregulare. 1969. Agnihotri, V. P. Mycologia 59:967-980.
Issued by: Great Lakes Forestry Centre
Catalog ID: 33110
Availability: PDF (request by e-mail)
Appressoria of Pythium irregulare are club-shaped bodies that can be clearly differentiated into a stalk and head. The size of stalk and the size and shape of head are affected by environmental and nutritional factors. Approximately 48% of the appressoria produced a single infection peg, but in others the number ranged from 2 to 9. In several cases the infection peg arose laterally instead of distally. Dichotomous branching of proliferating germ tubes resulted in an infection pad. Temperatures from 15 to 25 C and pH from 6.0 to 7.0 stimulated abundant production of appressoria. Of 14 carbohydrates tested, glucose yielded the most, and rhamnose the least appressorial production. Complex organic nitrogen sources (yeast extract, peptone, and casein hydrolysate) were superior to the other nitrogen sources tested. Of several amino acids tested, threonine induced the best appressorial production and valine the poorest. The addition of biotin and inositol stimulated abundant production of appressoria. The pyrimidine moiety of thiamine was superior to that of the thiazole moiety, Except for P.,thi,m, oligOl,drr"", all other Pytlri,,,,, species tested produced appressoria; but club-shaped appressoria were usually produced by members of the P. irreglliare complex.