Management of paddy bunt (Tilletia barclayana) through mechanical seed processing

Paddy bunt or kernel smut of rice caused by Tilletia barclayana (Syn. Neovossia barclayana, N. horrida) is major disease of rice growing countries. Seeds of two lots of Pusa 44 variety produced during kharif 2014 and one lot produced during kharif 2015 were processed. Pre-cleaner and screen grader removed 44.7, 34.8 and 42.2% of total bunt infected seed present in the three seed lots and reduced bunt infection from 1.32 to 0.73, 1.58 to 1.03 and 3.05 to 1.76%, respectively. Eighteen combination treatments comprising of three deck slopes (S-1-2.5(0), S-2-2.0(0), S-3-1.5(0)), three feedings (F-1-9 kg, F-2-12 kg, F-3-15 kg per minute) and two output settings (O-1-30cm deck width, O-2-40cm deck width) of specific gravity separator were studied with an objective of getting maximum bunt free seed per unit of time. Maximum seed recovery (13.27 and 13.31 and 13.60 kg/minute) and bunt infection in final product (0.44, 0.41 and 0.46%) with 89.1, 89.7 and 92.3% recovery efficiency was obtained by the treatment S3F3O2 (slope of deck 1.5(0), feeding 15 kg/minute, output deck width 40 cm) in the three seed lots. Thus, mechanical processing reduced bunt infection by more than 65%, depending on the intensity of infection, as well as increased seed quality i.e. seed germination improved by 6.5% and physical purity by 5.34%.