An evalution of the nitrous acid – 3-methyl-2-benzothiazolinone hydrazone hydrochloride – ferric chloride assay for chitin in rust fungi and rust-infected tissue

Abstract

The growth of the bean rust and cowpea rust fungi was examined in cultivars of French bean and cowpea using light microscopy and the nitrous acid – 3-methyl-2-benzothiazolinone hydrazone hydrochloride – ferric chloride assay for chitin. Comparison of the results indicated that the chitin assay did not detect changes in vegetative growth but only detected substances present in mature and developing urediospores. Examination of urediospores indicated that the reactive component(s) was hexosamine, probably glucosamine, but not chitin. The presence of strongly reactive substances in the urediospores, and the apparent low level of chitin in vegetative mycelium compared with that in the mycelium of the commercial mushroom, suggest that this chitin assay is of little value in estimating rust fungus growth in infected plant tissue.