The purpose of this study was to analyze the problems that must be resolved in the short and long term to improve rice productivity in Nicaragua, where the current rice self-sufficiency rate is 73%. First, after selecting varieties with high adaptability to various cultivation environmental conditions, it is necessary to thoroughly manage seed purity to supply certified seeds. In rice cultivation technology, it needs to improve seedling standing and weeding effect by improving soil leveling, and watersaving cultivation technology. Also, proper fertilization and planting density must be established in irrigated and rain-fed areas. In addition, it is necessary to strengthen the capacity by collecting and training with the latest agricultural technology information, by revitalizing the union rather than the individual farmer. It is necessary to develop varieties highly adaptable to the Nicaragua cultivation environment, as well as to expand irrigation facilities and cultivation technology suitable for weather conditions June- July in rain-fed areas. Last, it is necessary to maintain the consistency of agricultural policy for continuous and stable rice production, in response to climate change such as drought or intermittent heavy rain.

In the rice inflorescence development, timing of inflorescent meristem abortion, conversion of the rachis branch meristem to the terminal spikelet meristem and shift to lateral meristem identity determine the overall architecture of the rice panicle (keda-Kawakatsu et al. 2009). Cheng et al. (2011) reported that quantitative trait loci (QTLs) have major effects on panicle apical abortion in rice. However, there have been very few reports about panicle tip mutants. Therefore, this research is conducted to fine map mutant gene and perform functional analysis of mutant gen. Hwacheongbyeo (japonica rice) seed was treated with ethyl methane sulfonate (EMS) for inducing mutation. Two F2 population (Japanica mutant crossed with wild type and Japanica mutant crossed with Milyang 23, Indica type) were established for Phenotyping and genomic analysis. STS markers in crop molecular Breeding laboratory. Additional STS markers for fine mapping were developed based on the Nipponbare genome sequence (http://rgp.dna.affrc.go.jp/blast/runblast.html). All F2 generations showed the segregation of normal plants and mutant following a ratio of 3:1 suggesting the mutant phenotype is caused by a single recessive gene. Initial BSA test made using STS markers confirmed the mutant gene is found in the long arm of chromosome 8. Panicle tip mutant gene, pnt has pleotropic effect which has been manifested in significant reduction of tiller development starting from late stage of vegetative growth and pronounced effect on possession of stay green nature of the rice during the vegetative stage of development. The only significant difference observed within panicle traits is the number of spikelet on primary branch and spikelet fertility. The first primary branch which contain aborted spikelet and elongated distance between spikelet is the most affected structure in the panicle.

Single nucleotide polymorphisms (SNPs) are the most abundant variation in plant genomes. As DNA markers, SNPs are rapidly replacing simple sequence repeats (SSRs) and sequence tagged sites (STSs) markers, because SNPs are more abundant, stable, easy to automation, efficient, and increasingly cost-effective. We developed a 96-plex indica/japonica SNP genotyping set for genetic analysis and molecular breeding in rice using Fluidigm platform. Informative SNPs for indica/japonica populations were selected from 1536 Illumina SNPs and 44K Affymetrix SNP chip data of Rice Diversity and our resequencing data sets. Selected SNPs were evenly distributed across 12 chromosomes and average physical distance between adjacent SNP markers was 4.38Mb. We conducted genetic diversity analysis of 49 Bangladesh germplasm and check varieties to test a 96-plex indica/japonica SNP genotyping set we developed. High-throughput Fluidigm SNP genotyping system will serve a more efficient and valuable tool for genetic diversity analysis, DNA fingerprinting, quantitative trait locus (QTL) mapping and background selection for crosses between indica and japonica in rice. 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.

Tongil (IR667-98-1-2) rice, developed in 1972, is a high-yielding rice variety derived from a three-way cross between indica and japonica. Tongil contributed to staple food self-sufficiency of Korea, an achievement that was termed the ‘Korean Green Revolution’. In this study, we analyzed the nucleotide-level genome structure of Tongil rice and compared it to those of the parental varieties. A total of 17.3 billion Illumina Hiseq reads, 47× genome coverage, were generated from Tongil rice. Three parental accessions, two indica and one japonica types, of Tongil rice were also sequenced for approximately 30x genome coverage. A total of 2,149,991 SNPs were detected between Tongil and Nipponbare; the average SNP frequency of Tongil was 5.77 per kb. Genome composition based on the SNP data by comparing with the three parental genome sequences on sliding window of Nipponbare genome sequence revealed that 91.8% of the Tongil genome originated from the indica parents and 7.9% from the japonica parent, different from the theoretical expectation in a three-way cross, i.e., 75% indica and 25% japonica parental origins on average. Copy number of SSR motifs, ORF gene distribution throughout the whole genome, gene ontology (GO) annotation, yield-related QTLs or gene locations, and polymorphic transposon insertions were also comparatively analyzed between Tongil and parents using sequence-based tools. The results indicated that each genetic factor was transferred from parents into Tongil in proportion to the whole-genome composition. The Tongil rice is the first successful superior cultivar derived from indica × japonica hybridization in Korea. Defining of genome structure demonstrates that the Tongil genome is composed mostly of the indica genome with a small proportion of japonica genome introgression. 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.

Hybrid sterility is a critical barrier of inter-subspecific crosses in rice. However, hybrid sterility can be overcome by wide compatibility variety. The HWC-line of rice had slender grain shape, tall culm length, wide compatibility with both indica and japonica cultivars. For QTL analysis of HWC-line, two F2 populations were derived from the crosses between the HWC-line and each of two Korean variety, Dasan (Korean Tongil-type cultivar) and Hwacheong (temperate japonica cultivar). In the cross between HWC-line/Dasan (HD), 93 STS markers and 13 SSR markers were mapped on 12 chromosomes. In the population from HWC-line/Hwacheong (HH) cross, 28 STS markers, 29 SSR markers and 1 FNP marker were mapped on 11 chromosomes. Eight agronomic characters were evaluated for QTL analysis in two F2 populations and parents. The F2 population from HD cross revealed 21 M-QTLs and 3 E-QTL for culm length, spikelet per panicle, spikelet fertility, grain length, grain width, grain shape and 100 grains weight. 8 QTLs of culm length, grain length, grain width and grain shape were newly detected in this study. In the F2 population from HH cross, 17 M-QTLs were detected for culm length, panicle length, spikelet fertility, grain length, grain width, grain shape and 100 grains weight. 6 QTLs of culm length, grain length, grain width and grain shape were newly found in this study. These QTLs will be able to provide basic information on putative functional genes related with agronomic characters and promote breeding new rice cultivar. HWC-line could be used as bridge for inter-subspecies crosses and in hybrid breeding.

The HWC-line of rice showed wide compatibility with both indica and japonica cultivars, tall culm length, long and slender grain shape. For QTL analysis, two F2 populations were derived from the crosses between the HWC-line and each of two Korean variety, Dasanbyeo (Korean Tongil-type cultivar) and Hwacheongbyeo (temperate japonica cultivar), respectively. A total of 190 F2 plants were evaluated in each of two F2 populations. Eight agronomic characters were measured for QTL analysis in F2 populations and parents. Two molecular linkage maps were constructed. In the F2 population from cross between HWC-line / Dasanbyeo (HD) cross, 93 STS markers and 13 SSR markers were mapped on 12 chromosomes, covering a total length of 1942.6 cM, with an average distance of 18.33cM between adjacent markers. In the F2 population from HWC-line / Hwacheongbyeo (HH) cross, 28 STS markers, 29 SSR markers and 1 FNP marker were mapped on 11 chromosomes, spanning a total length of 925.53cM, with an average distance of 15.96cM between adjacent markers. In the F2 population from HD cross, 16 M-QTLs and 1 E-QTL were detected for culm length, spikelets per panicle, spikelet fertility, grain length, grain width, grain shape and 100 grains weight. 7 QTLs of spikelet fertility, grain length, grain width and grain shape were newly identified in this study. In the F2 population from HH cross, 15 M-QTLs were detected for culm length, panicle length, spikelet fertility, grain length, grain width, grain shape and 100 grains weight. 6 QTLs of culm length, grain length, grain width and grain shape were newly identified in this study. The QTLs identified in this study would provide basic information on putative functional genes related agronomic characters and facilitate breed new rice cultivar.