Screening lowland rice varieties for resistance to brown spot disease in Enyong creek rice field in Akwa Ibom state of Nigeria

Abstract

Twelve lowland rice varieties (BG 90-2, Cisadane, FARO 12, FARO 15 (early maturing), FARO 15 (late maturing), IR 5, ITA 123, ITA 306, MAS 2401, Suakoko 8 and TOS 2578) were planted in 2008 and 2009 growing
seasons in Enyong creek rice field in Akwa Ibom State. The varieties were screened for resistance to brown spot disease under natural infection conditions. Disease severity was assessed by counting the total number of spots per plant and by measuring the diameter of the spots. Data were collected at 6, 9 and 12 weeks after transplanting. Using number of spots per plant as parameter for assessing brown spot severity, results showed that ITA 123 and Suakoko 8 recorded the lowest number of spots and Cisadane and IR 5, the highest. Taking size of spots per plant as another
parameter, the smallest spots were observed in ITA 123 and Suakoko 8 and the largest in ITA 212 and IR 5. Evaluation of resistance of the varieties showed that of the twelve varieties screened, two (ITA 123 and Suakoko 8) representing 16.67% were resistant, three (ITA 306, ITA 212 and BG 90-2) or 25.00% were moderately susceptible, six (FARO 15 (early maturing), TOS 2578, MAS 2401, FARO 12, FARO 15 (late maturing) and IR 5 or 50.00% were susceptible and one (Cisadane) or 8.33% was highly susceptible. No variety was found to be highly resistant, that is,
completely free of spots. The two resistant varieties,ITA 123 and suakoko 8, are recommended to rice farmers in this agroecology.