Effect of applied silica on the process of infection and blast development of finger millet caused by Pyricularia grisea Sacc.

Finger millet is predominantly grown as rain fed crop by small farmers and disease management by chemical means is found to be economically unviable. Hence, it would be useful for the disease to be managed with the application of silica fertilizers. Development of the host plant resistance against blast by the application of silica fertilizers is one of the important aspects in the management of plant diseases. Several early events during primary inviasions by Pyricularia grisea determine the success of the host relationship. They are the germination of conidia, formation of appressoria, formation of haustoria, penetration peg and papilla at the encounter site which influence further progress of the pathogen (Johnson 1979). The present investigations were conducted during 2002–03 at UAS, GKVK, Bangalore, three finger millet genotypes such as K-7, KM-245 and IE-1012 were procured from the small millets project at UAS, GKVK, Bangalore and two silica fertilizers such as calcium silicate (Ca Sio₃) and sodium silicate (Na₂ Sio₃, 9 H₂O) laboratory grade were used in the present study in pot experiments to test the effect of silica fertilizers on disease development of blast. In the present study, size of the blast lesion (mm²) caused by blast on three ragi genotypes viz., K-1, KM-245 and IE-1012 treated with sodium silicate and calcium silicate was recorded. The size of the lesion is significantly reduced in resistant variety IE-1012 when compared to the susceptible variety K-7 and moderately susceptible variety KM-245 and as the concentration of applied silica increased there was a considerable reduction in the size of the lesion. The genotypes treated with calcium silicate recorded lower leaf blast lesion size when compared to the genotypes treated with sodium silicate. The genotypes treated with calciumsilicate recorded less per cent of neck blast and finger blast when compared to the genotypes treated with sodium silicate. Further, inhibition of germ tube length and appressoria diameter was observed in the resistant genotypes compared to the susceptible. Whereas the genotypes treated with high rate of calcium silicate and sodium silicate resulted in significant reduction in conidial germination, appressoria formation, appressoria diameter and germ tube length of the pathogen. These findings are in agreement with Carver and Cass (1977) Carver and Adgaibe (1990). Hence, calcium silicate may be used as fertilizer to manage the blast disease of finger millet at recommended dose.