Bacterial pustule is a major bacterial disease in most soybean-growing regions of Korea, resulting in soybean yield reductions of up to 60%. In this study, we aimed to understand the differences in disease severity caused by three strains of Xanthomonas citri pv. glycines, including two newly differentiated strains (K29 and K100) and the conventional representative strain, 8ra. Seventeen major soybean cultivars and 14 breeding lines were inoculated and compared for their reactions to the three strains of Xcg. The two new strains caused higher levels of disease severity, resulting in a greater number of susceptible cultivars. The landrace PI 547711, like Williams 82, was highly resistant to all Xcg strains; however, the other six cultivars that were resistant to 8ra, including Daepung2, were susceptible to the new strains (K29 and K100). In particular, the most widely grown cultivars, Daewon and Daepung2, were highly susceptible to K100. All of the breeding lines except two were also vulnerable to the new strains, K100 and K29. Of the breeding lines, SS05004-1-1-4-2-3-4 and SS05022-5-4-2-4-4-4 were resistant to the three Xcg strains, at similar levels to that of Williams 82. The breeding lines and cultivars evaluated in this study may be used to develop breeding materials resistant to new Xcg strains in the future. In addition, establishment of an improved disease evaluation system for bacterial pustule, by using multiple representative strains, is strongly recommended for breeding programs, to increase the efficiency and accuracy of selection for resistance as the pathogenic diversity of X. citri pv. glycines changes.

This study was carried out to select waxy corn inbreds with good general combining ability through a diallel analysis of 10 half diallel crosses among five inbreds developed from Korean maize landraces. Total of 21 agronomic and palatability traits were investigated over two locations in 2016. There was a significant hybrid by location interaction found in plant height, ear height, number of tillers/plant, per ear weight, ear tip filling, ear commercial value and sweetness when four additional check cultivars were included in the analyses. A significant general combining ability by location interaction was found in ear height, number of tillers/plant, per ear weight, ear length and sweetness while ear width, ear commercial value and sweetness were significant for specific combining ability by location interaction. Sweetness was found significant for both interactions. The first and fourth inbred lines had the most number of traits with good estimate of general combining ability. The first inbred is expected to improve days to tasseling, anthesis silking interval, ear width, ear circumference and sweetness while decreasing husk cover in a hybrid combination. The fourth inbred line would improve days to tasseling, days to silking, plant height, ear height, per ear weight and ear length but ears would be a bit tougher than the average. A total of 19 traits had higher variance of general combining ability than that of specific combining ability. Husk cover was 12.1 times higher. Plant height and number of tillers/plant had higher variance of specific combining ability.

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.