Study of the Differentiation of Fusarium oxysporum f.sp. albedinis Chlamydospores on Different Culture Media

Abstract

Chlamydospores of Fusarium oxysporum f.sp. albedinis are well known as fungus survival spores in soil, also act as a causal agent of Bayoud disease of the date palm. Till now, there are a little study in the literature about the favorable media for the formation of chlamydospores and the stages of chlamydogenesis. This study shows that rice flour based medium (45 chlamydospores per mm2), oatmeal (31 chlamydospores per mm2) and bean flour (27 chlamydospores per mm2) tested for the first time, are among the media inducing the formation of chlamydospores in large numbers. The optimum formation of chlamydospores is observed on rice flour-based medium after 7 days of incubation at 18°C and pH 7. The effect of light does not seem very important on chlamydogenesis. However, relative humidity has a significant effect on the growth and chlamydogenesis of F. oxysporum f.sp. albedinis. The tested G1 isolate grows and forms chlamydospores at relative humidities of 70 and 100%. The number of chlamydospores varies between 40.01 and 44.05 chlamydospores/mm2. To form chlamydospores, cultures of F. oxysporum f.sp. albedinis need to be in contact with the favorable culture medium. Thus, the cultures develop and form more chlamydospores on a single layer of cellophane deposited on a culture medium, but show slower growth and do not form chlamydospores on two layers of cellophane. Chlamydospores of Fusarium oxysporum f.sp. albedinis are always at the extremity of the mycelial filaments. They differ in one to four cells in superimposed position. A terminal hyphal bulge leads to the formation of the terminal cell. The second cell is formed at the base of the first, and the process continues so that one can sometimes observed chlamydospores in bead-like chains.