Effect of media, light and pH on growth and spore production by Alternariaeichhorniae, a mycoherbicide agent for waterhyacinth

Alternaria eichhorniae is being developed as a bioherbicide agent for contr olling waterhyacinth (Eichhornia crassipes) in Egypt. A virulent isolate, A . eichhorniae 5 (Ae5), was studied to determine the optimum media, light an d pH conditions for its cultural growth and spore production. The best medi a for the linear growth were waterhyacinth-fresh potato dextrose agar and w aterhyacinth dextrose agar (WHDA) while lima bean agar (LBA) and modified R ichard's agar were the least favorable for mycelial growth. Abundant spores were produced by Ae5 on LBA followed by WHDA. The maximum linear growth of mycelium as well as the best sporulation on the solid media were obtained from cultures grown in unwrapped plates under continuous light at 30 degree sC. Hydrogen ion concentration also had an effect on growth. At pH 7, the b est mycelial growth but the least spore production were obtained. A large n umber of spores was produced at pH 5.6 and pH 9.7; however, at these pH lev els only moderate and sparse amounts of mycelial growth were obtained, resp ectively. Of the four spore production methods evaluated, an adaptation of Walker's method was the most effective with respect to time, materials, and the number of spores produced.