Culture media promoting sporulation of rice kernel smut fungus Tilletia barclayana

Rice kernel smut, caused by Tilletia barclayana, is an important fungal disease in rice worldwide. It can cause considerable losses of yield and milling quality in epidemic years. Having a culture medium able to stimulate the sporulation of the fungus is desirable for in vitro, greenhouse and field studies. However, no research has been conducted to develop optimal culture media for the growth and sporulation of T. barclayana. In this research, studies were conducted using four isolates of the fungus to evaluate various agar media, carbon sources, and incubation periods on the growth and sporulation of this fungus. Of the six culture media evaluated, rice bran agar (RBA) was the best medium in promoting sporulation, producing secondary sporidia of up to 1.95 × 106 sporidia/ml, while the water agar-only medium produced the least number of secondary sporidia (< 2 × 105 sporidia/ml). Potato dextrose agar (PDA) and potato sucrose agar (PSA) were the two media most effective in stimulating mycelial growth. Carbon source (sucrose, dextrose, and D-sorbitol) in culture media significantly affected the sporulation of the fungus but not mycelium growth. Incubation at 28 °C for 2 weeks under a 12 h light – 12 h darkness cycle resulted in the greatest sporulation of the four incubation periods (1, 2, 3 and 4 weeks) evaluated. The best culture medium and incubation time identified from this study could help facilitate the preparation of conidial inoculum for in vitro, greenhouse and field studies of kernel smut in rice.