Effect of D-amino acids on conidium size and numbers of pseudosepta per conidium in isolates of Bipolaris sorokiniana

Abstract

Isolates of Bipolaris sorokiniana grew to some extent on the D-isomers of 15 amino acids supplied as the sole nitrogen source. D-histidine did not support growth of any isolate. No conidia were produced by cultures grown on D-arginine. There was no consistent relationship between length of conidia produced by D- and L-isomers of the same amino acid. The trend was towards the production of shorter conidia on D-amino acids, although isolates varied considerably in their response. Conidia produced on D-phenylalanine were markedly shorter than those produced on the L-isomer, although isolates varied in the magnitude of response. A similar effect was recorded with aspartic acid as the nitrogen source but only in buffered medium. Conidia produced on D-ornithine were longer than those produced on L-ornithine, although this response was less-marked in buffered medium. Generally, the numbers of pseudosepta per conidium were higher in conidia produced on the L-isomer of individual amino acids. Although this increase in numbers usually paralleled the increased length of conidia, there was a large range in correlation coefficients between the two values over different isolate–substrate combinations.