Studies on growth response of some pathogenic species of Phyllosticta in different nitrogen media

Abstract

Summary The growth response of twelve species Phyllosticta was studied on eighteen different nitrogen sources. Amongst the nitrates, potassium nitrate was a very good source while ammonium nitrate was much inferior. Ammonium sulphate was a very poor source. None of the Phyllosticta species were capable of utilizing sodium nitrite. Most of the organic nitrogen substances like glycine, DL-alanine, L-glutamic acid, DL-aspartic acid, DL-valine, L-proline, asparagine and glutamine were invariably good sources. The value of L-arginine and DL-phenylalanine were variable for these isolates of Phyllosticta . L-histidine as well as two sulphur containing amino acids viz., L-cystine and DL-methionine were poor sources for all the present species. Varying pH patterns were recorded on different sources of nitrogen. The p h of potassium nitrate solution drifted towards neutrality after attaining considerable acidity by the 6th day. The final p h of the ammonium nitrate medium had also a tendency of drifting towards neutrality but the initial acidic trend continued for a longer time. The final p h of the ammonium nitrate solution did not reach beyond 5.2 in any case. Ammonium sulphate medium developed extreme acidity in shortest time and no upward trends were recorded during the incubation period. Addition of sodium salts of succinic or fumaric acid to ammonium sulphate solution prevented the fall of p h and normal growth was accomplished. The efficiency of the supplemented ammonium sulphate medium was better than asparagine for some of the organisms. Phyllosticta rnorifolia and P. pandanicola had better growth on supplemented ammonium sulphate medium while the influence of both the abon media was almost similar for P. bauhiniae , P. buteae and P. carica papayae . All the remaining species of Phyllosticta achieved better growth on asparagine than on ammonium sulphate fumarate or succinate media. The author is grateful to Professor R. N. T andon for his valuable suggestions