Chung-Kon Kim

Development of breeding lines with three pyramided resistance genes that confer broad-spectrum bacterial blight resistance and their molecular analysis in rice

BackgroundThe development of resistant cultivars has been the most effective and economical strategy to control bacterial leaf blight (BB) disease of rice caused by Xanthomonas oryzae pv. oryzae (Xoo). Molecular markers have made it possible to identify and pyramid valuable genes of agronomic importance in resistance rice breeding. In this study, three resistance genes (Xa4 + xa5 + Xa21) were transferred from an indica donor (IRBB57), using a marker-assisted backcrossing (MAB) breeding strategy, into a BB-susceptible elite japonica rice cultivar, Mangeumbyeo, which is high yielding with good grain quality.ResultsOur analysis led to the development of three elite advanced backcross breeding lines (ABL) with three resistance genes by foreground and phenotypic selection in a japonica genetic background without linkage drag. The background genome recovery of the ABL expressed more than 92.1% using genome-wide SSR marker analysis. The pathogenicity assays of three resistance-gene-derived ABL were conducted under glasshouse conditions with the 18 isolates of Xoo prevalent in Korea. The ABL exhibited very small lesion lengths, indicating a hypersensitive reaction to all 18 isolates of Xoo, with agronomic and grain quality traits similar to those of the recurrent parent. Pyramiding the resistance genes Xa4, xa5 and Xa21 provided a higher resistance to Xoo than the introduction of the individual resistance genes. Additionally, the combination of two dominant and one recessive BB resistance gene did not express any negative effect on agronomic traits in the ABL.ConclusionsThe strategy of simultaneous foreground and phenotypic selection to introduce multiple R genes is very useful to reduce the cost and the time required for the isolation of desirable recombinants with target resistance genes in rice. The resistance-gene-derived ABL have practical breeding value without a yield penalty by providing broad-spectrum resistance against most of the existing isolates of BB in South Korea and will have a high impact on the yield stability and sustainability of rice productivity.

Expression of BrD1, a plant defensin from Brassica rapa, confers resistance against brown planthopper (Nilaparvata lugens) in transgenic rices.

Plant defensins are small (5-10 kDa) basic peptides thought to be an important component of the defense pathway against fungal and/or bacterial pathogens. To understand the role of plant defensins in protecting plants against the brown planthopper, a type of insect herbivore, we isolated the Brassica rapa Defensin 1 (BrD1) gene and introduced it into rice (Oryza sativa L.) to produce stable transgenic plants. The BrD1 protein is homologous to other plant defensins and contains both an N-terminal endoplasmic reticulum signal sequence and a defensin domain, which are highly conserved in all plant defensins. Based on a phylogenetic analysis of the defensin domain of various plant defensins, we established that BrD1 belongs to a distinct subgroup of plant defensins. Relative to the wild type, transgenic rices expressing BrD1 exhibit strong resistance to brown planthopper nymphs and female adults. These results suggest that BrD1 exhibits insecticidal activity, and might be useful for developing cereal crop plants resistant to sap-sucking insects, such as the brown planthopper.

Growth performance and hematological traits of broiler chickens reared under assorted monochromatic light sources

A study was conducted to investigate the effect of different monochromatic lights on growth performance and hematological response of growing broiler chickens. A total of 360 one-day-old broiler chicks were randomly divided into 6 lighting treatments, which were replicated 6 times with 10 chicks in each replicate. Six light treatments include incandescent bulbs (as a control) and light-emitting diode white light, blue light, red light, green light, and yellow light (YL). The birds were provided with similar nutritional specifications and environmental management facilities, except for the lights throughout the experimental period. Growth performance was evaluated in terms of BW, BW gain, feed intake, and feed conversion ratio at weekly intervals. At the end of 5 wk, 2 birds from each replicate were randomly selected for blood collection to determine hematological response. The BW and feed intake was numerically higher in YL at 5 wk of age. But interestingly, this did not result in improved feed conversion ratio in YL; nevertheless, numerical values were lower in YL at 5 wk (P > 0.05). Red blood cells, blood platelet count, and percent hematocrit were numerically higher under YL, whereas white blood cell counts and percent hemoglobin remained unaffected due to light treatments. It was concluded that monochromatic light is a potential light source that might provide a beneficial effect on growth performance but is inconclusive for hematological measures of broilers.

Isolation and characterization of 28 polymorphic SSR loci from castor bean (Ricinus communis L.)

Castor bean (Ricinus communis) is cultivated for seed oil throughout tropical and subtropical regions but the understanding of its genetic variability is limited. Because applicable microsatellite markers are not sufficient, we isolated and characterized polymorphic simple sequence repeat (SSR) loci acquired from a microsatellite-enriched genomic DNA library of castor bean. Finally, 28 SSR loci revealed polymorphisms in a castor bean collection consisting of 72 accessions. A total of 73 alleles were detected, with an average of 3.18 alleles per locus, and the polymorphism information content (PIC) ranged from 0.03 to 0.47 (mean = 0.26). Values for observed (HO) and expected (HE) heterozygosity ranged from 0.00 to 0.19 (mean = 0.11) and from 0.04 to 0.54 (mean = 0.31), respectively. To understand genetic relationships within the castor bean collection, a dendrogram was constructed based on profiles of the 28 SSR loci. These newly developed SSRs will be useful tools for assessing genetic diversity and population structure in castor bean.

Influence of monochromatic light on quality traits, nutritional, fatty acid, and amino acid profiles of broiler chicken meat

The role of monochromatic lights was investigated on meat quality in 1-d-old straight-run broiler chicks (n = 360), divided into 6 light sources with 6 replicates having 10 chicks in each replicate. Six light sources were described as incandescent bulbs (IBL, as a control) and light-emitting diode (LED) light colors as white light (WL), blue light, red light (RL), green light, and yellow light. Among LED groups, the RL increased the concentration of monounsaturated fatty acids (P < 0.001), saturated fatty acids (P < 0.001), and the saturated:polyunsaturated fatty acid ratio (P < 0.001), but reduced the concentration of polyunsaturated fatty acid, n-3 fatty acid, and n-6 fatty acid. The IBL increased the n-3 and sulfur-containing amino acids but reduced the n-6:n-3 nonessential amino acids. The WL improved the concentration of most of the essential amino acids (P < 0.01) and nonessential amino acids (P < 0.01) of breast meat. It can be extracted that the light produced by LED responded similar to the IBL light in influencing nutrient contents of meat. Moreover, LED is not decisive in improving fatty acid composition of meat. However, the role of IBL in reducing n-6:n-3 ratio and enhancing n-3 cannot be neglected. Among LED, WL is helpful in improving essential and nonessential amino acid contents of broiler meat.

SSR Analysis of Genetic Diversity and Cold Tolerance in Temperate Rice Germplasm

A total of 23 elite rice cultivars from eight countries were evaluated for cold tolerance using two screening methods at Chuncheon Substation, National Institute of Crop Science (NICS), Republic of Korea. The rice cultivars Jinbu, Mustaqillik, and Avangard showed cold tolerance and high spikelet fertility (63-79%) in cold-water irrigation screening. Under greenhouse screening, five cultivars (Giza 177, Avangard, Mustaqillik, Jinbu, and Jungan) showed high cold tolerance and high spikelet fertility (71-81%). Simple sequence repeat (SSR) marker analysis of 21 genotypes revealed two major clusters, the japonica and indica groups, with a genetic similarity of 0.69. Out of 21 rice cultivars, only four (Giza 178 from Egypt, Attey and Zakha from Bhutan, and Millin from Australia) fell under the indica cluster. The cold-tolerant varieties Jinbu, Mustaqillik, and Avangard were clustered with the japonica group, which had genetic similarity of 0.83. These varieties are considered as potential germplasm that will help diversify the japonica gene pool for cold-tolerant rice breeding. A one-way linear analysis of variance identified a significant relationship between individual alleles and traits. Three SSR markers were significantly associated with spikelet fertility under cold-water irrigation on chromosomes 1, 2, and 7. Five SSR markers were associated with spikelet fertility under a cool-environment greenhouse on chromosomes 8, 9, 10, and 12. The SSR markers associated with cold tolerance may also be useful as selection markers in indica/japonica cross combinations to improve cold tolerance.

The physicochemical properties of kenaf(Hibiscus cannabinus L.) as mushroom culture media source

To investigate the usefulness of Kenaf(Hibiscus cannabinus L.) as mushroom culture media source, we analyzephysical condition and contents of nutritional components. The water absorption rate of Kenaf bast was 578% and it was 95%higher than that of poplar sawdust’s. This was caused by Kenaf’s porous cellular structure. so it could give more moisture andoxygen to cultured mushroom. Total carbon contents of Kenaf was 91.4%, it was quite higher than that of poplar sawdust, wheatbran and rice bran. Total nitrogen content was 1.76% and C/N ratio was 51.9. The content of NFE(Nitrogen free extract) was46.6% and it was similar with rice bran. Cellulose content was higher than poplar but lignin content was lower. speciallyhemicellulose and pectin complex which more digestible carbon source to mushroom was 3.7% higher than poplar. Mineralcomponent and amino acid contents were also maintained high compared with poplar. Fe was 4.2 times, P 3.2 times, K 2.2times more and Ca was higher 16 mg/kg than poplar. The content of amino acid was quite more higher than poplar sawdust butlower than chaff. Consequently Kenaf had a good trait for basic support material in mushroom culture media and also had agood character as nutritional source.

Changes of Weedy Rice Occurrence in Repeated Wet Direct Seeding and Alternate Transplanting/Wet Direct Seeding of Rice

Weedy rice is one of the major problems in direct-seeded rice field, resulting in poor rice quality and low grain yield. This study was carried out to evaluate the conversion effect to machine transplanting after wetdirect-seeding for 3 years on weedy rice occurrence, in comparison of repeated wet-direct-seeding. Occurrence of weedy rice in the continuous wet-hill-seeded and broadcasted field for 3 years increased 4 folds, when compared with that in machine transplanted rice paddy. In the first year of wet-direct-seeded field converted from machine transplanting, weedy rice occurrence did not increase, demonstrating lesser weedy rice in wet-hill-seeded than broadcasted field. These results indicate that alternate cultivation of wet-hill-seeding and machine transplanting is more effective to prevent weedy rice occurrence than the repeated wet-direct-seeding method for 3 years.