Production of Chlamydospores and Conidia in Submerged Culture by Rhynchosporium alismatis, a Mycoherbicide of Alismataceae in Rice Crops

The objective of this work was to evaluate the production of chlamydospores and conidia of Rhynchosporium alismatis in a liquid Czapex-Dox based medium supplemented with increasing concentrations of sodium nitrate and malt extract. In addition, the germination of chlamydospores was evaluated. A high concentration of malt extract (4.4 g L^-1) as the sole carbon source and a high level of sodium nitrate as the sole nitrogen source (3.3 g L^-1) were shown to increase chlamydospore production while agitation (150 rpm) enhanced conidial yields. Maximum chlamydospore production (2.03×10⁵±0.7 total chlamydospores mg DW^-1) was achieved in cultures grown in a medium supplemented with 8.8 g L^-1 malt extract and 5.74 g L^-1 sodium nitrate. Two days growth was required for maximum chlamydospore and conidial production, while 6 days was necessary to obtain maximum dry weight accumulation (350 mg per flask). Germination of chlamydospores (90%) was significantly higher than germination of conidia (47%) after 2 days growth.