The Influence of Nitrogen Sources on Growth and Protein Metabolism of Nectria haematococca Berk. & Br.

Abstract

Summary Isolate II (IMI No. 267377) of Nectria haematococca (Fusarium solani) was highly virulent for cvs. “Marglobe” and “Pusa Ruby” causing higher per cent of pre- and post-emergence killing of tomato seedlings. On the other hand isolate I (IMI No: 267376) had high virulence for cvs. “Punjab Chuhara”, “Best of All”, and “Early Dwarf”. In both isolates increase in mat accumulation was rapid and linear between 10–15 days of growth. Nitrogen source of the medium and age of the culture determined the variation in growth response, protein build up, protease activity and size and composition of amino acid pool. Protein accumulation, protease activity and amino acid composition which varied with age of culture could be indirect determinants of virulence of the isolates of N. haematococca . High protein content and high protease activity with profuse liberation of amino acids at an early growth stage enables 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.