viruses were injected to follicles on both wings for later studies. Chickens were raised in cages and observed on a daily basis over a two-month period. The regenerated feathers were plucked and examined with a dissection or scanning electron micrograph microscope for abnormalities compared with normal primary remiges. Histology and in situ hybridizationParaffin sections (5 mm) were stained with haematoxylin and eosin or prepared for in situ hybridization following routine procedures 26 . Cryostat sections (10 mm) were stained with X-gal. TUNEL staining was performed using a kit (Roche). Nonradioactive wholemount or section in situ hybridization or section in situ hybridization was performed according to the protocol described 22,26 . After hybridization, sections were incubated with an antidigoxigenin Fab conjugated to alkaline phosphatase (Boehringer Mannheim). Colour was detected by incubating with a Boehringer Mannheim purple substrate (Roche).

Easy shattering reduces yield due to grain loss during harvest in cereals. Shattering is also a hindrance in breeding programs that use wild accessions because the shattering habit is often linked to desirable traits. We characterized a shattering mutant line of rice, Hsh, which was derived from a nonshattering japonica variety, Hwacheong, by N-methyl-N-nitrosourea (MNU) treatment. The breaking tensile strength (BTS) of the grain pedicel was measured using a digital force gauge to evaluate the degree of shattering of rice varieties at 5, 10, 15, 20, 25, 30, 35, and 40 days after heading (DAH). The BTS of Hwacheong did not decrease with increasing DAH, maintaining a level of 180-240 gf, while that of Hsh decreased greatly during 10-20 DAH and finally stabilized at 50 gf. Optical microscopy revealed that Hsh had a welldeveloped abscission layer similar to the wild rice Oryza nivara (accession IRGC105706), while Hwacheong did not produce an abscission layer, indicating that the shattering of Hsh was caused by differentiation of the abscission layer. On the basis of the BTS value and morphology of the abscission layer of F 1 plants and segregation data in F 2 populations, it was concluded that the easy shattering of Hsh was controlled by the single recessive gene sh-h. The gene sh-h was determined to be located on rice chromosome 7 by bulked segregant analysis. Using 14 SSR markers on rice chromosome 7, the gene sh-h was mapped between the flanking markers RM8262 and RM7161 at distances of 1.6 and 2.0 cM, respectively. An SSR marker Rc17 cosegregated with the gene sh-h. The locus sh-h for shattering was tightly linked to the Rc locus conferring red pericarp, as well as a QTL qSD s -7-1 for seed dormancy, implying that this region might represent a domestication block in the evolutionary pathway of rice.

SUMMARYAlthough susceptibility to seed shattering causes severe yield loss during cereal crop harvest, it is an adaptive trait for seed dispersal in wild plants. We previously identified a recessive shattering locus, sh-h, from the rice shattering mutant line Hsh that carries an enhanced abscission layer. Here, we further mapped sh-h to a 34-kb region on chromosome 7 by analyzing 240 F 2 plants and five F 3 lines from the cross between Hsh and Blue&Gundil. Hsh had a point mutation at the 3¢ splice site of the seventh intron within LOC_Os07g10690, causing a 15-bp deletion of its mRNA as a result of altered splicing. Two transferred DNA (T-DNA) insertion mutants and one point mutant exhibited the enhanced shattering phenotype, confirming that LOC_Os07g10690 is indeed the sh-h gene. RNA interference (RNAi) transgenic lines with suppressed expression of this gene exhibited greater shattering. This gene, which encodes a protein containing a conserved carboxy-terminal domain (CTD) phosphatase domain, was named Oryza sativa CTD phosphataselike 1 (OsCPL1). Subcellular localization and biochemical analysis revealed that the OsCPL1 protein is a nuclear phosphatase, a common characteristic of metazoan CTD phosphatases involved in cell differentiation. These results demonstrate that OsCPL1 represses differentiation of the abscission layer during panicle development.

Using a population of recombinant inbred lines of the 164 genotypes derived from a cross between ÔMilyang 23Õ (indica) and ÔGihobyeoÕ (japonica) in rice (Oryza sativa L.), salt tolerance was evaluated at a young seedling stage in concentrations of 0.5% and 0.7% NaCl. Mapping quantitative trait loci (QTLs) related to salt tolerance was carried out by interval mapping using Qgene 3.0. Two QTLs (qST1 and qST3) conferring salt tolerance at young seedling stage were mapped on chromosome 1 and 3, respectively, and explained 35.5-36.9% of the total phenotypic variation in 0.5% and 0.7% NaCl. The favourable allele of qST1 was contributed by ÔGihobyeoÕ, and that of qST3 by ÔMilyang 23Õ. The results obtained in 0.5% and 0.7% NaCl for 2 years were similar in flanked markers and phenotypic variation.

RESEARCHI dentifying quantitative trait loci (QTLs) associated with economically valuable phenotypes is of particular interest as the basis for developing effi cient strategies for genomics-based approaches to plant improvement. Identifi cation of QTLs is also a valuable starting point for positional cloning of genes underlying quantitative phenotypes and for interpreting the molecular and biochemical mechanisms that condition plant growth and development.The QTL studies that are conducted over several years and locations provide information about which regions of the genome ABSTRACT A population of 164 recombinant inbred lines (RILs) of rice (Oryza sativa L.) derived from a cross between Milyang23 and Gihobyeo was evaluated for nine phenotypic characters over three years and two regions in Korea. The population had been previously mapped using 414 molecular markers. Genotype × environment (G × E) interaction was analyzed for six grain yieldrelated traits and three agronomic traits across years and locations using the AMMI model. The quantitative trait loci (QTLs) were detected by interval mapping and composite interval mapping. A total of 75 QTLs were identifi ed for the nine traits across fi ve environments and they were categorized as (i) 29 QTLs with main effect, (ii) 18 QTLs with minor effect, (iii) 13 QTLs with G × E interaction effect, (iv) six QTLs with both main effect and G × E interaction effect, and (v) nine potential QTLs with low log of the odds (LOD) scores. The AMMI model explained from 68.6% to 84.7% of the interaction effect and 19 QTLs were signifi cantly associated with G × E interaction. Culm length had the least G × E, while the maximum G × E interaction was exhibited for spikelets per panicle (39.7%) and percent ripened grain (35.3%). Markers closely linked to main effect QTLs will be most useful for marker-assisted breeding.