In monsoon climates, persistent shade is a troublesome weather condition with an impact on the growth and yield of corn (Zea mays L.). We imposed 7, 14, 21, and 28 days of consecutive shade (CS) on Gwangpyeongok and P3394 corn hybrids at the beginning of the kernel filling stages. Shade had little impact on leaf area and dry matter accumulation in the stem and leaves. However, dry matter accumulation in the ear was severely reduced by approximately 28% and 53% after 14 and 28 days of CS, respectively. For the components of grain yield, 7 and 14 days of shade did irreparable damage to the number of filled kernels, the kernel number per ear row, and the percent of filled kernels, but did little damage or reversible damage after removal of the shade to the 100-grain weight and the row number per ear. Shade significantly reduced the relative growth rate (RGR) due to a decrease in the net assimilation rate (NAR). These results suggest that source activity limitation by shade during the kernel filling stages leads to the inhibition of sink activity and size. The yield of biomass, ear, and grain logistically declined as the length of CS increased. Probit analysis revealed that the number of days of CS needed to cause 25% and 50% reductions in grain yield were 3.7 and 23.1, respectively. These results suggest that the plant yield loss induced by shade at the beginning of the kernel filling stages is mainly achieved within the first 7 days of consecutive shade.

Understanding how crops interact with their environments is increasingly important in breeding program, especially in light of highly anticipated climate changes. A total of 150 recombinant inbred lines (RILs) of F12 generation derived from Dasanbyeo (Indica) x TR22183 (Japonica) were evaluated at Suwon 2010, Shanghai 2010, IRRI 2010 wet season, Suwon 2011, Shanghai 2011, IRRI 2011 dry season, and IRRI 2011 wet season as a total of seven diverse environments. Traits evaluation included eight important agronomical traits such as days to heading (DTH), culm length (CL), panicle length (PL), panicle number per plant (PN), spikelet number per panicle (SN), spikelet fertility (SF), 100-grain weight (GW), and grain yield (GY). As a result of genotyping using 384-plex GoldenGate oligo pool assay (OPA) set (RiceOPA3.1), the linkage map for 235 SNP markers covering a total of 926.53 cM with an average interval of 4.01 cM was constructed and a total of 44 main-effect quantitative trait loci (QTL)s and 35 QTLs by environment interaction (QEI) were detected for all eight traits using single environment and multi-environments analysis, respectively. Of these, fourteen putative QTLs for DTH, CL, PN, SN, GW and GY found in single environment analysis had the similar position to QEI for those traits, suggesting that these same QTLs from both single-and multi-environments are major and stable for certain traits. To the best of our knowledge, 12 QTLs consisted of four QTLs for CL (qCL2, qCL8.1, qCL8.2, and qCL8.3), six QTLs for GW (qGW3.1, qGW3.2, qGW7, qGW8, qGW10.1, and qGW10.2), one QTL for GY (qGY3) and one for SF (qSF4) out of 44 QTLs obtained from single environment analysis were considered to be novel since no overlapping QTL was reported from previous studies. In addition, 12 out of 35 QTLs obtained from multi-environments analysis were also novel.

Rice embryo contains valuable materials which are related to human health and industrial material, thus controlling embryo size is more and more important in the field of rice breeding. Especially, main health-aid components such as γ -aminobutyric acid (GABA), tocopherol and vitamins showed positive-correlation with embryo size. We obtained three enlarged embryo character mutants derived from Hwacheongbyeo (Korean japonica cultivar) by treatment of chemical mutagen, N-methyl-N-nitrosourea(MNU). These three mutants were named according to their embryo size as ge-m, ge, ge-s. The result of allelism test between Hwacheongbyeo, ge-m, ge and ge-s represented that the embryo size of ge and ge-s was controlled by the same gene(Giant embryo, GE). Through GE locus sequencing of three mutants, we found that each of ge and ge-s mutant has a point mutation, causing non synonymous amino acid substitution. On the other hand, ge-m mutant, the embryo of which featured intermediate size in between those of Hwacheongbyeo and ge, turned out to be non-allelic to the GE locus, suggesting it is likely a novel gene, which influences rice embryo development through a different mechanism than GE gene. Fine mapping of ge-m is currently in progress. This work was supported by a grant from the Next-Generation BioGreen 21 Program (Plant Molecular Breeding Center No. PJ008125), Rural Development Administration, Republic of Korea.

The rice sucrose synthase 3 (RSUS3) localized predominantly inrice seed endosperm may play an important role in the starch filling in the milky stage of rice seed. As the genetic diversity at this locus is not known yet, forty three rice varieties/accessions were objected to amplify full sequence of the RSUS3 to examine the distribution of DNA polymorphisms. A total of 254 sequence variants, including 82, 150 and 22SNP sand indels, were successfully identified in whole length of 7,733bp sequence comprising promoter, exon and intron, and 3’ down stream non transcribed region(NTR). Eleven haplotypes were distinguishable among 43 rice varieties based on the nucleotide variation on the three defined regions (5’NTR, transcript and 3’NTR). The promoter region showed the occurrence of a base change on a cis-element which might involve a functional role of the motif in seed-specific expression. Non random process seemed to be acted in the genetic diversity of RSUS3geneamongricegermplasmusedinthisstudy. The analysis of polymorphism sites indicated a history of eleven minimum recombination mostly occurred in the transcribed region. This result might provide an insight for a clasditic approach for establishing future genetic association studies of RSUS3locus.

Sucrose synthase 3 which is a third active gene present in rice, is localized predominantly in rice endosperm. This sucrose synthase 3 may play an important role in the starch filling in the milky stage rice seed, probably involving in the starch physicochemical properties. As the genetic diversity at this locus is little informed, forty three rice consisting of japonica, indica and Oryza rufipogon were targeted to amplify full sequence of sucrose synthase 3 to examine the frequency and distribution of nucleotide polymorphism. Total of 755 all sequence variants detected, 491 single nucleotide polymorphisms (SNPs) and 264 indels were successfully identified in 7618 bp of sequence containing the sucrose synthase 3 transcript, promoter and 3' non-transcribed region. The frequency of nucleotide changes and indels were high, on average one polymorphism per 15.5 bp and one indel per 28.9 bp with 11 sequence-based haplotypes distinguishable among the varieties and lines. Both the frequency of nucleotide changes and indels were frequent in non-coding region, but rare in coding region. Sequencing a polymorphism region in the promoter showed one base change on one of cis-element from T (CATGCATA to A (CATGCACA) that might implicate in seed specificity. The presence of a high number of haplotype shared by a few varieties indicated a little information on linkage disequilibrium.

The giant embryo(ge) mutation was genetically mapped to chromosome 7 by Koh et al. The ge mutations were analyzed at the morphologic and genetic level by Hong et al. And this publication linked the GE gene as being required for proper endosperm development. Researchers in Dupont cloned the GE gene, sequenced and characterized the ge alleles of the mutants. the three giant embryo mutant lines we obtained by treating MNU to Hwacheongbyeo, a japonica type Korean rice cultivar, differed in their embryo and endosperm size and their embryo/endosperm ratios. We named these alleles affecting the embryo size in rice GE, ge-m, ge, ge-s (GE: the wild type, ge-m: embryo slightly larger than in the wild type, ge: large embryo, ge-s: embryo even larger than in ge). The ORFs and introns of the four different alleles in the GE locus were sequenced and compared with the corresponding sequences in the patent that dupont presented. Each mutant alleles sequence showed a few SNPs in the ORF region. Two SNPs were shared among the three mutant lines and each mutant line hab one or two additional SNPs. Further studies are in progress regarding the GE RNA expression level in each mutant line and the F1 seed phenotypes and allelism relationship among the mutant lines.

Barley Yellow Dwarf Virus (BYDV) has been a major disease causing a severe loss of yield in winter cereals worldwide. It has been recently reported that BYDV occurs frequently in wheat field and also causes serious yield reduction in Korea. This study was performed to investigate the regional distributions of BYDV strains in Korea and to identify the resistant cultivars or lines of wheat to the predominant BYDV strains, providing basic information for the breeding of BYDV-resistant wheat varieties. Using RT-PCR and EcoRI digestion methods, the regional distribution of BYDV strains in Korea from 1999 to 2000 showed that PAV strain was mainly detected about 65% (Vic-PAV 52.6% ; CN-PAV 47.4%) and MAV strain about 3%. Using ELISA test for the examination of BYDV resistance with 17 cultivars and 4 lines among Korean wheat, three cultivars, Gurumil, Topdongmil, and Olgurumil, were susceptible to BYDV and the others were resistant. In plant growth and yield component responses to BYDV infection, Gurumil showed significant difference between the uninfected and the infected, suggesting the most susceptible to BYDV among Korean wheat, but Eun-pamil and Seohae118 did no difference, an indication that they have the highest resistance.

Barley Yellow Dwarf Virus (BYDV), an aphid-borne luteovirus, is a major plant pathogenic disease causing a huge economic loss in the grain production of a wide range of Gramineae species throughout the world. It has been recently reported that BYDV also occurred frequently in wheat field of Korea. Here, we performed to develop the detection and classification methods of BYDV strains that were accomplished by reverse transcription-polymerase chain reaction (RT-PCR). Since there are high variations among BYDV strains, three pairs of primers were designed to detect BYDV strains such as PAV (Vic-PAV and CN-PAV) and MAV (primer A) simultaneously, specifically Vic-PAV(primer B), and MAV (primer C) based on the genomic RNA sequences of BYDV strains previously published. The validity of the primers was confirmed using several BYDV strains obtained from CIMMYT. Though three BYDV strains were able to be detected using primer A, PCR products were not distinguished between two PAV strains. It was possible to separate them with a restriction enzyme, EcoRI, whose restriction site was present in the amplified DNA fragment from Vic-PAV, but not from CN-PAV.