Exploration of suitable solid media for mass multiplication of Cochliobolus lunatus and Alternaria alternata used as mycoherbicide for weed management (barnyard grass) in rice.
Fungal pathogens viz. Cochliobolus lunatus and Alternaria alternata were isolated from barnyard grass (Echinochloa crusgalli) and their pathogenicity was re-confirmed on same weed through various bioassays using spore suspension of both pathogens under green house conditions. For development of formulations of these mycoherbicide, large biomass is required and it is essential to find cheaper growth media to reduce the cost of the product. For this purpose, various solid substrates such as wheat and its bran, rice and its bran, broken sorghum and E. crusgalli seeds supplemented with yeast extract and molasses were used for mass multiplication of these weed pathogens. Among six substrates tested, rice supplemented with molasses (10 g/L) and yeast extract (3.0 g/L) produced highest conidia for both mycoherbicide after 14 days with 12 h photoperiod at 25°C. The pathogenicity test with conidia obtained from both pathogens was conducted on 5 leaf stage of E. crusgalli and rice under glass house conditions. The results revealed that 100% mortality of the target weed within 14 days after treatment (DAT) and no effect on rice.