A Special Method to Confirm Non-Feasibility of Secondary Spread of Downy Mildew Systemic Infection between Sorghum Seedlings of Similar Age

A method has been devised to test the possibility of spread of secondary infection in green-house experiments in case of downy mildew of sorghum. Treatment pots were planted with inoculated sprouts in the peripheral ring and sown with seeds in the centre to study disease transmission from periphery to the centre. In the treatment pots containing a peripheral ring of 6 days old sporulating seedlings and central seedlings of 1-2 days age, 46% disease transmission from periphery to centre was recorded. In pots with 6 days old peripheral sporulating seedlings and central seedlings of 3-4 days age, disease transmission was 13% and in pots where peripheral and central seedlings were both of 6 days age, no transmission was recorded. Results indicate that disease transmission between siblings of same age is not feasible in greenhouse or field conditions.