Sodium Alginate for Production and Formulation of Mycoherbicides

Abstract

Sodium alginate was used to prepare pelletized formulations for each of five fungi. Aqueous mixtures of 1.0% (w/v) sodium alginate and homogenized mycelia of Alternaria cassiae Jurair & Khan, Alternaria macrospora Zimm., Fusarium lateritium Nees ex Fr., Colletotrichum malvarum (A. Braun & Casp.) Southworth, or a Phyllosticta sp. were pelletized by dropwise additions of each mycelial-alginate mixture into 0.25 M CaCl2. Abundant conidia were produced on the pellets 24 to 48 h after the pellets were spread into trays and exposed 10 min/12 h to 275-W sunlamps. These conidia germinated readily (90 to 100%) and readily infected the respective host plants. Each liter of mycelium plus growth medium from submerged liquid cultures produced 4 L of the mycelial-alginate mixture. Each liter of the mycelial-alginate mixture produced approximately 18 g of air-dried formulation. When 10% (w/v) clay was incorporated into the pellets, each liter of the mycelial-alginate mixture produced approximately 118 g of air-dried formulation. The pelletized fungi sporulated readily following storage at 4 or 25 C for 6 to 8 months. This method of pelletization is potentially useful for the formulation of inoculum of fungi used as mycoherbicides, for the mass production of pycnidium-forming fungi, and for the production of inoculum for host-plant resistance studies.