Blast resistance of 29 rice cultivars confirmed as a durable resistance in the evaluation of sequential planting from 2004 to 2006 was evaluated to nursery screening in 14 test sites during 11 years in Korea. The average disease severity (ADS) of 29 rice varieties against rice blast showed 3.5 degree; however, the difference of disease severity among the varieties was from 1.9 to 4.8. The 29 varieties were grouped into resistance less than 3.0 ADS degree including 12 varieties and moderate resistance over 3.1 ADS degree including 17 varieties. Among the 12 rice cultivars presented low ADS, 4 rice cultivars, Ungwang, Pungmi 1, Sinunbong 1, and Dasan 1 were constantly appeared high resistant reaction during 11 years in all test sites and the others were showed various diseases severity across the test years and the test sites. Twenty-one rice cultivars including Gopum were more variable among the test sites while the others were higher variable among the test years. These results indicated that durable resistance test against rice blast using sequential planting is a very efficient screening method to predict durability and nursery test for long periods and also useful method to predict indirectly durable resistance of rice cultivars.

The increase in carbon stock and sustainability of crop production are the main challenges in agricultural fields relevant to climate change. Methane is the most important greenhouse gas emitted from paddy fields. This study was conducted to investigate the effects of tillage and cultivation methods on methane emissions in rice production in 2014 and 2015. Different combinations of tillage and cultivation were implemented, including conventional tillage-transplanting (T-T), tillage-wet hill seeding (T-W), minimum tillage-dry seeding (MT-D), and no-tillage-dry seeding (NT-D). The amount of methane emitted was the highest in T-T treatment. In MT-D and NT-D treatments, methane emissions were significantly decreased by 77%, compared with that in T-T treatment. Conversely, the soil total carbon (STC) content was higher in MT-D and NT-D plots than in tillage plots. In both years, methane emissions were highly correlated with the dry weight of rice (R 2 = 0.62~0.96), although the cumulative emissions during the rice growing period was higher in 2014 than in 2015. T-T treatment showed the highest R 2 (0.93) among the four treatments. Rice grain yields did not significantly differ with the tillage and cultivation methods used. These results suggest that NT-D practice in rice production could reduce the methane emissions and increase the STC content without loss in grain yield.