THE INFLUENCE OF NITROGEN-SOURCES ON GROWTH AND PROTEIN-METABOLISM OFNECTRIA-HAEMATOCOCCA BERK AND BR

Isolate II (IMI No. 267377) of Nectria haematococca (Fusarium solani) was highly virulent for cvs. ''Marglobe'' and ''Pusa Ruby'' causing hi gher per cent of pre- and post-emergence killing of tomato seedlings. On the other hand isolate I (IMI No: 267376) had high virulence for cv s. ''Punjab Chuhara'', ''Best of All'', and ''Early Dwarf''. In both i solates increase in mat accumulation was rapid and linear between 10-1 5 days of growth. Nitrogen source of the medium and age of the culture determined the variation in growth response, protein build up, protea se activity and size and composition of amino acid pool. Protein accum ulation, protease activity and amino acid composition which varied wit h age of culture could be indirect determinants of virulence of the is olates of N. haematococca. High protein content and high protease acti vity with profuse liberation of amino acids at an early growth stage e nables the pathogen to cause pre-emergence death of tomato seedlings. Similarly, late stage accumulation of protein by the pathogen enhances virulence and results in prominent post-emergence damping off of the seedlings.