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Grain size is a quantitative trait with a complex genetic mechanism, characterized by the combination of grain length (GL), grain width (GW), length to width ration (LWR), and grain thickness (GT). In this study, we conducted quantitative trait loci (QTL) analysis to investigate the genetic basis of grain size using BC1F2 and BC1F2:3 populations derived from two indica lines, Guangzhan 63-4S (GZ63-4S) and TGMS29 (core germplasm number W240). A total of twenty-four QTLs for grain size were identified, among which, three QTLs (qGW1, qGW7, and qGW12) controlling GL and two QTLs (qGW5 and qGL9) controlling GW were validated and subsequently fine mapped to regions ranging from 128 kb to 624 kb. Scanning electron microscopic (SEM) analysis and expression analysis revealed that qGW7 influences cell expansion, while qGL9 affects cell division. Conversely, qGW1, qGW5, and qGW12 promoted both cell division and expansion. Furthermore, negative correlations were observed between grain yield and quality for both qGW7 and qGW12. Nevertheless, qGW5 exhibited the potential to enhance quality without compromising yield. Importantly, we identified two promising QTLs, qGW1 and qGL9, which simultaneously improved both grain yield and quality. In summary, our results laid the foundation for cloning these five QTLs and provided valuable resources for breeding rice varieties with high yield and superior quality. [ABSTRACT FROM AUTHOR]

The presented study sought to phenotype the rice cultivars procured from the Unique Scientific Installation (USI) - Collection of Federal Scientific Rice Centre, Krasnodar, Russian Federation, as sources of valuable grain quality traits, as well as BC2 populations with the selection of the best genotypes for quality traits in developing the red grain rice cultivars with high nutritional properties. The studied rice plant material, grown in the artificial climate chambers of FSBSI - Federal Scientific Rice Centre, had the following conditions: temperature - 28-30 °C during the day (12 h) and 24 °C at night (12 h); illumination - 30,000 lux, and humidity = 70%. Rice determination and phenotyping for grain quality traits commenced on high-tech certified equipment per GOSTs. The experiment results had the parental genotypes used in the backcrossing program assigned to the group of medium-grain cultivars, except for the long-grain cultivars, i.e., Svetlana and Gagat. The 1000-grain weight ranged from 23.0 to 27.4 g, filminess (17.8% to 19.9%), and total milling yield (65.0% to 70.4%). Low fracturing appeared in rice cultivars, viz., Rubin, Alliance, Kurazh, Gagat, and VNIIR10163, while a high vitreosity emerged in rice cultivars Veles, Svetlana, VNIIR10163, and Khaw-sri-nin. BC2 plant populations' evaluation depended on the technological quality traits. The effective heterosis was evident for most grain quality traits. Rice genotypes selected based on lower fracturing and higher grain size will undergo further breeding work to develop the high-yielding rice genotypes with desirable grain quality traits. [ABSTRACT FROM AUTHOR]

SUMMARY: Optimal grain‐appearance quality is largely determined by grain size. To date, dozens of grain size‐related genes have been identified. However, the regulatory mechanism of slender grain formation is not fully clear. We identified the OsSG34 gene by map‐based cloning. A 9‐bp deletion on 5'‐untranslated region of OsSG34, which resulted in the expression difference between the wild‐type and sg34 mutant, led to the slender grains and good transparency in sg34 mutant. OsSG34 as an α/β fold triacylglycerol lipase affected the triglyceride content directly, and the components of cell wall indirectly, especially the lignin between the inner and outer lemmas in rice grains, which could affect the change in grain size by altering cell proliferation and expansion, while the change in starch content and starch granule arrangement in endosperm could affect the grain‐appearance quality. Moreover, the OsERF71 was identified to directly bind to cis‐element on the mutant site, thereby regulating the OsSG34 expression. Knockout of three OsSG34 homologous genes resulted in slender grains as well. The study demonstrated OsSG34, involved in lipid metabolism, affected grain size and quality. Our findings suggest that the OsSG34 gene could be used in rice breeding for high yield and good grain‐appearance quality via marker‐assisted selection and gene‐editing approaches. Significance Statement: The gene OsSG34, its three homologous genes, involved in lipid metabolism network, could play an important role in grain‐appearance quality by altering cell proliferation and expansion. The OsERF71 directly bound to cis‐element on the mutant site and upregulated OsSG34 expression. [ABSTRACT FROM AUTHOR]

The source strength and sink demand as well as their interaction have been demonstrated to co-regulate the synthesis of starch and determine the grain quality, but the knowledge of the underlying physiological mechanisms is limiting. An indica variety, Yangdao 6, and a japonica variety, Jinxiangyu 1, were planted with three treatments, including normal growth plant (CK), leaf-cutting (LC) and spikelet-thinning (ST). The transcript levels of starch metabolic genes, physicochemical characteristics of starch and appearance, milling, cooking and tasting qualities of rice under different treatments were determined. The ST treatment increased the relative expression of genes related to the synthesis of short branch-chains of amylopectin (SSI, BEI, BEIIb) and amylose (GBSSI) and reduced the relative expression of medium-long to long branch-chains of amylopectin synthesis genes (SSIIa, SSIIIa, SSIIIb, ISA1). When comparing ST with the CK treatment, starch granules became smoother with higher contents of short branch-chains and lower ratios of medium-long and long branch-chains of amylopectin; the crystallinity and the value of 1045/1022 cm−1 was decreased; for pasting properties, the setback and pasting temperature were decreased; the peak viscosity, hot viscosity, breakdown and final viscosity were significantly increased. Meanwhile, the ST treatment improved the appearance, milling and cooking and tasting qualities. The opposite results were observed under the LC treatment. These results indicated that source strength and sink size would regulate expression levels of starch metabolic genes, which is pivotal for the contents of amylose and short/long branch chains ratio of amylopectin, thus changing the structure and physicochemical properties of starch and grain quality. Here, we speculated that the improved source strength in terms of higher leaf/canopy photosynthesis and small sink size, such as small panicle size, would be preferred traits in high grain quality rice breeding. [ABSTRACT FROM AUTHOR]

OsMADS1 plays a vital role in regulating floret development and grain shape, but whether it regulates rice grain quality still remains largely unknown. Therefore, we used comprehensive molecular genetics, plant biotechnology, and functional omics approaches, including phenotyping, mapping-by-sequencing, target gene seed-specific RNAi, transgenic experiments, and transcriptomic profiling to answer this biological and molecular question. Here, we report the characterization of the 'Oat-like rice' mutant, with poor grain quality, including chalky endosperms, abnormal morphology and loose arrangement of starch granules, and lower starch content but higher protein content in grains. The poor grain quality of Oat-like rice was found to be caused by the mutated OsMADS1Olr allele through mapping-by-sequencing analysis and transgenic experiments. OsMADS1 protein is highly expressed in florets and developing seeds. Both OsMADS1-eGFP and OsMADS1Olr-eGFP fusion proteins are localized in the nucleus. Moreover, seed-specific RNAi of OsMADS1 also caused decreased grain quality in transgenic lines, such as the Oat-like rice. Further transcriptomic profiling between Oat-like rice and Nipponbare grains revealed that OsMADS1 regulates gene expressions and regulatory networks of starch and storage protein metabolisms in rice grains, hereafter regulating rice quality. In conclusion, our results not only reveal the crucial role and preliminary mechanism of OsMADS1 in regulating rice grain quality but also highlight the application potentials of OsMADS1 and the target gene seed-specific RNAi system in improving rice grain quality by molecular breeding. [ABSTRACT FROM AUTHOR]

Quantitative trait loci (QTLs) and HQTL (heterosis QTLs) for grain shape are two major genetic factors of grain yield and quality in rice (Oryza sativa L.). Although many QTLs for grain shape have been reported, only a few are applied in production. In this study, 54 QTLs for grain shape were detected on 10 chromosomes using 33 SSSLs (single-segment substitution lines) and methods of statistical genetics. Among these, 23 exhibited significant positive additive genetic effects, including some novel QTLs, among which qTGW4-(1,2), qTGW10-2, and qTGW10-3 were three QTLs newly found in this study and should be paid more attention. Moreover, 26 HQTLs for grain shape were probed. Eighteen of these exhibited significant positive dominant genetic effects. Thirty-three QTLs for grain shape were further mapped using linkage analysis. Most of the QTLs for grain shape produced pleiotropic effects, which simultaneously controlled multiple appearance traits of grain shape. Linkage mapping of the F2 population derived from sub-single-segment substitution lines further narrowed the interval harbouring qTGW10-3 to 75.124 kb between PSM169 and RM25753. The candidate gene was identified and could be applied to breeding applications by molecular marker-assisted selection. These identified QTLs for grain shape will offer additional insights for improving grain yield and quality in rice breeding. [ABSTRACT FROM AUTHOR]

Rice is a major food crop that sustains approximately half of the world population. Recent worldwide improvements in the standard of living have increased the demand for high-quality rice. Accurate identification of quantitative trait loci (QTLs) for rice grain quality traits will facilitate rice quality breeding and improvement. In the present study, we performed highresolution QTL mapping for rice grain quality traits using a genotyping-bysequencing approach. An F2 population derived from a cross between an elite japonica variety, Koshihikari, and an indica variety, Nona Bokra, was used to construct a high-density genetic map. A total of 3,830 single nucleotide polymorphism markers were mapped to 12 linkage groups spanning a total length of 2,456.4 cM, with an average genetic distance of 0.82 cM. Seven grain quality traits--the percentage of whole grain, percentage of head rice, percentage of area of head rice, transparency, percentage of chalky rice, percentage of chalkiness area, and degree of chalkiness--of the F2 population were investigated. In total, 15 QTLs with logarithm of the odds (LOD) scores >4 were identified, which mapped to chromosomes 6, 7, and 9. These loci include four QTLs for transparency, four for percentage of chalky rice, four for percentage of chalkiness area, and three for degree of chalkiness, accounting for 0.01%-61.64% of the total phenotypic variation. Of these QTLs, only one overlapped with previously reported QTLs, and the others were novel. By comparing the major QTL regions in the rice genome, several key candidate genes reported to play crucial roles in grain quality traits were identified. These findings will expedite the fine mapping of these QTLs and QTL pyramiding, which will facilitate the genetic improvement of rice grain quality. [ABSTRACT FROM AUTHOR]

Grain size, shape and weight are important factors influencing grain yield and quality of rice. They are mostly determined by grain length (GL) and grain width (GW). A 13.2 Mb interval, RM167–RM287 on chromosome 11 of rice, was previously found to be associated with variations in 1000-grain weight (TGW). In this study, three populations derived from the indica rice cross Teqing/IRBB52 were used to identify and validate quantitative trait loci (QTLs) controlling GL, GW, TGW and the ratio of GL to GW (RLW) in the RM167–RM287 region. First, two QTL clusters associated with these traits were detected using two populations, segregating the RM167–RM287 interval only. One controlled GL, GW and TGW and was designated as qGS11. The other controlled GL and RLW. The allelic directions of the two QTL clusters on GL were opposite. Then, qGS11 was further mapped in a 1.4 Mb interval using near-isogenic lines, showing a small effect on GL and a relatively large effect on TGW, GW and RLW. Meanwhile, a stable and small effect on the heading date was detected. The allelic direction for the heading date was the opposite for TGW and GW but the same for GL and RLW. The results suggest that qGS11 has the potential for application in rice breeding. [ABSTRACT FROM AUTHOR]

Rice is the most staple food consuming in China. During the past six decades, a large number of indica inbred rice cultivars have been developed. However, seldom studies have focused on evaluating the dynamic changes of grain quality improvement among the major cultivars. Our study evaluated the genetic improvement of 12 quality traits in indica inbred rice cultivars developed in rice breeding programs in South China during 1956–2020. The results indicated that significant improvement had been gained for the appearance quality, cooking and eating quality in the breeding program since the 1990s, while slight genetic improvement was attained before 1990. Among all the 12 traits, MGL (Milled Grain Length), LWR (Length Rate Ratio), GC (Gel Consistency), and ASV (Alkali Spreading Value) were significantly increased among these different cultivars; MGW (Milled Grain Width), CGR (Chalky Grain Rate), CA (Chalkiness Area), and AC (Amylase Content) showed a tremendously decreased trend from last thirty years. However, the other four traits, such as BRR (Brown Rice Rate), MRR (Milled Rice Rate), HMRR (Head Milled Rice Rate), and PC (Protein Content) showed little improvement during the breeding processes in these cultivars. The results also suggested that selecting a slender grain shape would be beneficial for breeding high quality indica rice. We also discussed that improving milling quality, especially HMRR of the high-quality cultivars and nutrition quality for special consumer groups as an meaningful direction for rice breeding. [ABSTRACT FROM AUTHOR]

Appearance and taste are important factors in rice (Oryza sativa) grain quality. Here, we investigated the taste scores and related eating‐quality traits of 533 diverse cultivars to assess the relationships between—and genetic basis of—rice taste and eating‐quality. A genome‐wide association study highlighted the Wx gene as the major factor underlying variation in taste and eating quality. Notably, a novel waxy (Wx) allele, Wxla, which combined two mutations from Wxb and Wxin, exhibited a unique phenotype. Reduced GBSSI activity conferred Wxla rice with both a transparent appearance and good eating quality. Haplotype analysis revealed that Wxla was derived from intragenic recombination. In fact, the recombination rate at the Wx locus was estimated to be 3.34 kb/cM, which was about 75‐fold higher than the genome‐wide mean, indicating that intragenic recombination is a major force driving diversity at the Wx locus. Based on our results, we propose a new network for Wx evolution, noting that new Wx alleles could easily be generated by crossing genotypes with different Wx alleles. This study thus provides insights into the evolution of the Wx locus and facilitates molecular breeding for quality in rice. [ABSTRACT FROM AUTHOR]

In rice (Oryza sativa), amylose content (AC) is the major factor that determines eating and cooking quality (ECQ). The diversity in AC is largely attributed to natural allelic variation at the Waxy (Wx) locus. Here we identified a rare Wx allele, Wxmw, which combines a favorable AC, improved ECQ and grain transparency. Based on a phylogenetic analysis of Wx genomic sequences from 370 rice accessions, we speculated that Wxmw may have derived from recombination between two important natural Wx alleles, Wxin and Wxb. We validated the effects of Wxmw on rice grain quality using both transgenic lines and near‐isogenic lines (NILs). When introgressed into the japonica Nipponbare (NIP) background, Wxmw resulted in a moderate AC that was intermediate between that of NILs carrying the Wxb allele and NILs with the Wxmp allele. Notably, mature grains of NILs fixed for Wxmw had an improved transparent endosperm relative to soft rice. Further, we introduced Wxmw into a high‐yielding japonica cultivar via molecular marker‐assisted selection: the introgressed lines exhibited clear improvements in ECQ and endosperm transparency. Our results suggest that Wxmw is a promising allele to improve grain quality, especially ECQ and grain transparency of high‐yielding japonica cultivars, in rice breeding programs. [ABSTRACT FROM AUTHOR]

Breeding new rice varieties with high Eating and Cooking Quality (ECQ) characteristics is an important goal in rice breeding programs. To this end, 242 Recombinant Inbred Lines (RILs) of two populations derived from Alikazemi/IR67017-180-2-1-2 and Alikazemi/Saleh crosses were evaluated in two environments. The main and epistatic QTLs and QTL × Environment (Q × E) interactions were analyzed using the Mixed-Model-based Composite Interval Mapping method. A total of 17 main QTLs with additive effects were mapped on 6 rice chromosomes, including 6 QTLs for Amylose Content, 5 QTLs for Gelatinization Temperature and 6 QTLs for Gel Consistency. Seven QTLs were found on chromosome 6 associated with a common RM4128 marker (close to the Alk locus) influencing the ECQ characteristics with favorable alleles from the common female parent. Five QTL clusters were identified on chromosome 6, 7, 8, and 9, suggesting that the co-located QTLs with pleiotropic effects may control ECQ traits. A major QTL cluster was found for AC and GC between RM4128 and RM549 markers close to the Alk locus on chromosome 6, which is in the vicinity of another QTL located in RM587-RM4128 interval. 13 QTL pairs were identified to have a significant epistatic, Additive × Additive effects involved in controlling ECQ traits. A small phenotypic variation was found for the epistatic QTLs and Q × E interactions, suggesting the complexity of ECQ inheritance traits in rice. Further comprehensive studies and validation of the detected QTLs could be useful for marker-assisted selection to improve grain quality in rice. [ABSTRACT FROM AUTHOR]

Background: In temperate rice cultivation regions, japonica rice cultivars are grown preferentially because consumers deem them to have good eating quality, whereas indica rice cultivars have high grain yields and strong heat tolerance but are considered to have poor eating quality. To mitigate the effects of global warming on rice production, it is important to develop novel rice cultivars with both desirable eating quality and resilience to high temperatures. Eating quality and agronomic traits were evaluated in a reciprocal set of chromosome segment substitution lines derived from crosses between a japonica rice cultivar 'Koshihikari' and an indica rice cultivar 'Takanari'. Results: We detected 112 QTLs for amylose and protein contents, whiteness, stickiness, hardness and eating quality of cooked rice grains. Almost of 'Koshihikari' chromosome segments consistently improved eating quality. Among detected QTLs, six QTLs on chromosomes 1–5 and 11 were detected that increased whiteness and stickiness of cooked grains or decreased their hardness for 3 years. The QTLs on chromosomes 2–4 were not associated with differences in amylose or protein contents. QTLs on chromosomes 1–5 did not coincide with QTLs for agronomic traits such as heading date, culm length, panicle length, spikelet fertility and grain yield. Genetic effects of the detected QTLs were confirmed in substitution lines carrying chromosome segments from five other indica cultivars in the 'Koshihikari' genetic background. Conclusion: The detected QTLs were associated with differences in eating quality between indica and japonica rice cultivars. These QTLs appear to be widely distributed among indica cultivars and to be novel genetic factors for eating quality traits because their chromosome regions differed from those of the GBSSI (Wx) and SSIIa (Alk) genes. The detected QTLs would be very useful for improvement of eating quality of indica rice cultivars in breeding programs. [ABSTRACT FROM AUTHOR]

Rice research in Korea during the past 100 years has gone through tremendous changes and improvements as the country underwent a turbulent history of transformation. Full-scale R&D modernization began in the 1970s, when the government focused policy on achieving self-sufficiency in rice in order to establish the foundation for national economic growth. A major landmark was reached by the development of the rice variety “Tongil” and its cultivation technology, which was at the core of the unprecedented Korean “Green Revolution”. Since achieving self-sufficiency in rice, the breeding goal of Korea moved from increasing yield to improving grain quality as more consumers began to seek high quality food products in the 1980s. This change led to the establishment of the high quality rice breeding platform for enhancing the global competitiveness of Korean rice to cope with the opening of domestic rice market in the 2000s. Currently, the major breeding goals in rice are developing premium quality cultivars for table rice and specialized cultivars for boosting processed food industry. To date, the National Institute of Crop Science has released a total of 300 rice cultivars, including 202 table rice and 98 specialized usage cultivars. Diverse technologies have been developed and utilized for breeding new rice cultivars to meet changing needs. In the next 100 years of rice breeding, the convergence of traditional crop improvement technologies and the new breeding technologies utilizing recent advances in biotechnology will play a crucial role in enhancing breeding efficiency. [ABSTRACT FROM AUTHOR]

Thirty-six rice genotypes were evaluated for thirteen different quality parameters along with yield/plant to assess genetic estimates of the traits and the extent of genetic diversity among the varieties. Analysis of variance was conducted to determine GCV, PCV, heritability and GA of the genotypes with respect to all characters. Significant variation was observed in many traits among the genotypes offering scope for selection. Correlation analysis determined the nature of relationship among these characters. UPGMA studies revealed six major clusters and cluster I and II were the largest with maximum number of genotypes. The study identified that the varieties namely, Black Gora, Kalinga-2, Dudheswar, ARC 10086, IR-36, IR-64 and Nipponbare possessed good quality traits and high yield performance. The current study indicated that developing rice varieties for consumer acceptance with good grain quality traits along with high yield will be very useful in rice breeding and in selection of parents for hybridization to combine both high yield and improved quality traits. [ABSTRACT FROM AUTHOR]

Heading date, a complex quantitative trait, determines regional adaptability and is associated with grain yield and quality in rice. In this study, we characterized qHd2-1, a minor-effect quantitative locus (QTL) for promoting heading date (by 3–4 days) under long-day (LD) conditions, but not short-day (SD) conditions. The qHd2-1 locus was detected in single segment substitution line (SSSL) N22-1, which was developed using indica 9311 as the donor and japonica Nipponbare (NP) as the recipient. A set of substitution lines were developed from a segregating population derived from a cross between N22-1 and NP. Based on the genotypic identification and phenotypic evaluation of the target substitution lines, qHd2-1 was narrowed down to a 105-kb region between STS2-20 and STS2-22 on the short arm of chromosome 2. Furthermore, qHd2-1 was found to function by upregulating the florigen genes Hd3a and RFT1 during floral induction under LD conditions. Field tests showed that qHd2-1 promotion of heading date affects grain yield‑related agronomic traits, such as plant height, panicle number per plant, and flag leaf size, as well as thousand-grain weight and grain width. Taken together, these findings establish a foundation for cloning this minor-effect QTL involved in heading date, and qHd2-1 could be of great significance in rice breeding to allow the fine-tuning of heading date in rice cultivars. [ABSTRACT FROM AUTHOR]

Grain shape is a key factor that influences both grain yield and quality of rice (Oryza sativa L.). In order to elucidate the genetic basis of grain shape, an F2 and derived F2:3 populations were developed from a cross between Guangzhan63-4S (GZ63-4S) and TGMS29, and used in a quantitative trait locus (QTL) analysis. A total of thirty-six QTLs were identified for grain shape and weight, and the phenotypic variance explained by each QTL ranged from 0.88 to 35.70%. Given that most of the QTLs were detected in only one population, a BC1F2 and derived BC1F2:3 populations were constructed with GZ63-4S as the recurrent parent to further verify the QTLs. Seventeen QTLs were validated in at least one population. qGL1.3, the major QTL for grain length in both the F2 and F2:3 populations, contributed 41.16% of the variation in grain length and 35.96% of the variation in 1000-grain weight in a random BC1F3 population, and thus was selected for further fine mapping. Based on progeny tests of 31 recombinants, qGL1.3 was delimited to a region of about 350 kb on chromosome 1. These results could lay the foundation for map-based cloning of qGL1.3 and provide genes or QTLs for breeding rice lines with high grain yield and quality. [ABSTRACT FROM AUTHOR]

‘Yechan’ is a high grain quality mid-late maturing rice cultivar with lodging tolerance and multiple disease resistance. It was a derived from a cross between ‘Hopum’ and ‘Iksan537’ (cultivar name ‘Haepum’). ‘Hopum’ is a high grain quality mid-late maturing rice cultivar with strong lodging tolerance and ‘Haepum’ is a high grain quality medium maturing rice cultivar with multiple disease resistance. To shorten the breeding period, another culture method was applied to the F1 plants. ‘Yechan’ was selected through the pedigree method, yield trials, and local adaptability tests, with a high selection pressure for grain quality, lodging, and disease resistance. The heading date of ‘Yechan’ was August 14, one day later than that of ‘Nampyeong’. ‘Yechan’ is a cultivar tolerant to lodging and it has short culms. It has multiple disease resistance against rice blast, rice stripe virus, and bacterial blight, including the K3a race, the most virulent race in Korea. The yield of ‘Yechan’ was similar to that of ‘Nampyeong’. ‘Yechan’ showed excellent grain appearance, superior taste when cooked, and enhanced milling performance; thus, we concluded that it could contribute to the improvement of Korean japonica rice cultivar quality. ‘Yechan’, a high grain quality mid-late maturing rice cultivar with lodging tolerance and multiple disease resistance, would be suitable for cultivation in the southern plain area in Korea and has been utilized in the breeding programs aimed at enhancing the grain quality and stability for the cultivation of Korean japonica rice (Registration No. 7647). [ABSTRACT FROM AUTHOR]

The conditions of rice vegetation for four years (2014-2017) were analyzed. It was found that the air temperature and the sum of the effective temperatures above 15 degrees had deviations from the average multiyear in different phases of growth and development. But on the whole they contributed to the normal formation of rice yield. In experiments on rice breeding in a competitive trial, flve new rice varieties were studied in comparison with the universal variety Rapan in nine parameters. It is found that VNIIR 10257 signiflcantly exceeded the standard by yield (by 9.9 c/ha). Variability of yields by years was average (CV = 12.9-21.1%). The variability of yield at the level of the standard Rapan (CV = 14%) is noted in VNIIR 10262 and VNIIR 10257. Vegetation period in the studied genotypes was characterized by low variability, both the average by experiment (CV = 3.5-6.6%), and the average annual for each variety (CV = 0.4-6.2%). The mass of 1000 grains in Rapan and VNIIR 10243 strongly correlated positively with average daily temperatures (r = 0.77 and 0.82, respectively); and in VNIIR 10257 it was negative (r = -0.80). A close high correlation of the content of head rice content with heat supply was found in Rapan and VNIIR 10262 (r = 0.84 and 0.73). The remaining varieties were characterized by moderate and low correlation of the trait. A close positive relation between head rice content and the yield is observed in VNIIR 10243 (r = 0.97). In other varieties, the connection between yield and quality is highly negative. Based on the analysis of the obtained data, VNIIR 10257 (high-yield round-grained) and VNIIR 10262 (large-grained with high technological parameters of grain and milled rice quality) were transferred to the State Variety Test (SVT). New varieties showed high productivity and have a reaction similar to the standard for the variability of the main economic-valuable traits, which gives grounds to talk about their wide adaptive capabilities. [ABSTRACT FROM AUTHOR]

Panicle length (PL), an important yield‐related trait, strongly affects yield components, such as grain number, grain density and rice quality. More than 200 panicle length quantitative trait loci (PL QTLs) are identified, but only a small number are applied in rice breeding. In this study, we performed QTL analysis for PL using 42 single‐segment substitution lines (SSSLs) derived from nine donors in the genetic background of HJX74. Fourteen QTLs and five heterosis QTLs (HQTLs) for PL were recognised. Three QTLs and four HQTLs acted positively, and the other eleven QTLs and one HQTL acted negatively. By scanning the single heterozygous background region of the F2 population with large‐genetic‐effect SSSLs, we mapped PL loci qPL6‐2 and qPL7‐1 to different locations on chromosomes 6 and 7, respectively, in three consecutive years of independent trials. The genetic effects of these QTLs were further assessed. qPL6‐2 demonstrated the most positive additive effect (QTL), whereas qPL7‐1 achieved the most positive dominant effect (HQTL) for PL. These results indicated that the pyramiding of PL QTLs might increase grain yield and facilitate the application of the beneficial allele in hybrid rice breeding. [ABSTRACT FROM AUTHOR]

Rice is staple food in Iran. Despite of high quality of local rice, their grain yield is low. In hybridization breeding programs, selection of suitable parents is an essential role for developing new combinations with broadens genetic diversity. Combining ability of local rice varieties namely 'Hashemi', 'Sang Jo' and 'Tarom Deylamani' and 'Nemat' was evaluated in a partial diallele analysis for agronomic traits in a randomized complete block design at Sari Agricultural Sciences and Natural Resources University. General combining ability (GCA) and specific combining ability (SCA) variances showed predominated role of additive gene effects in the inheritance of grain length. Both additive and non-additive components of genetic variances were important in the inheritance of traits like grain yield, plant height, panicle length, total grains per panicle, grain length and grain length to width. However, non-additive gene effects were seen for tiller number. Results showed that 'Nemat' was the best general combiner for most of characters followed by 'Tarom Deylamani'. The cross of 'Hashemi' × 'Tarom Deylamani' was suggested to exploitation of heterosis breeding for increasing yield and its components in rice breeding programs [ABSTRACT FROM AUTHOR]

• A novel method for intelligent analysis of rice yield traits was developed based on LED transmission imaging and cloud computing. • A low-cost, non-radiation, and efficient imaging method had been proposed based on 624.4 nm red light, which was able to acquire high-contrast images of filled and unfilled grains. • A robust and accurate rice grain detection model had been developed to identify filled and unfilled rice grains in red-light images, and the specified algorithms had been designed to achieve high accuracy measurement of rice yield traits. • Qt-based local software and web-based application had been designed, which provided novel and convenient tools for rice breeding and genetic analysis. Rice yield traits extraction is necessary for rice breeding and genetic analysis, in which the discrimination of filled and unfilled grain was the bottleneck. The traditional methods including wind separating and water sinking are inefficient, unreliable, and poorly reproducible, meanwhile the machine vision methods based on X-ray and 3D structured imaging have the disadvantages of high cost, ionizing radiation, and poor scalability. To address the above problems, this study has proposed a novel method for intelligent analysis of rice yield traits based on LED transmission imaging and cloud application. The study has found that the red-light LED transmission imaging was able to obtain high-contrast images of filled and unfilled grains and had the advantages of radiation-free, low-cost, and high-efficiency imaging. Using 3,200 rice grain images as the training set, the results showed that the YOLOv5 model outperformed the Faster RCNN, RetinaNet, SSD, and Cascade RCNN models, and its filled and unfilled grain recognition precision was 98.94% and 90.96% on the 800 test sets, while the recall rate was 97.91% and 94.94%. To further improve the recognition accuracy of the YOLOv5 model, five model optimization methods were adopted in the study, including TPH, CBAM, adding a small target detection layer, using Bi-FPN and Multi-NMS. The results proved that the accuracy of unfilled grain recognition had significantly improved, the recognition precision increased by 4.54% to 95.44%, and the recall rate increased by 0.77% to 95.71%. Finally, this study has designed the specified algorithms based on the recognized rectangular box, which could accurately measure filled and unfilled grain numbers, seed setting rate and grain shape parameters. Moreover, the study has designed a local Qt software and a cloud-based website, which can support the simultaneous input of multiple images with high real-time performance and good scalability, providing a practical novel tool for rice breeding and genetic analysis. [ABSTRACT FROM AUTHOR]

The appearance of brown rice grown under high temperature conditions is an important characteristic for improvement in Japanese rice breeding programs. We performed a QTL analysis of the appearance quality of brown rice using chromosome segment substitution lines of the indica cultivar 'Habataki' in the 'Koshihikari' genetic background. A line carrying a 'Habataki' segment on chromosome 7 showed a high percentage of perfect grains produced under high temperature conditions during the ripening period. To verify the role of this segment, and to narrow down the region containing the useful allele, substitution mapping was performed using multiple paired lines. As a result, the chromosomal location of a gene that we named Appearance quality of brown rice 1 (Apq1) was delimited to a 48-kb region. In addition, we developed an Apq1-near isogenic line (NIL) to evaluate the effect of Apq1 on various agronomic traits. Under high temperature conditions during the ripening period, the Apq1-NIL produced significantly higher percentages of perfect grains than 'Koshihikari'. Other agronomic traits, including yield and palatability, were similar between the Apq1-NIL and 'Koshihikari'. Therefore, the 'Habataki' allele of Apq1 will be useful in breeding programs aimed at improving the quality of grains ripened under high temperature conditions. [ABSTRACT FROM AUTHOR]

The demand for superior grain quality represents a major issue in rice ( Oryza sativa L.) breeding. To study the genetic basis of rice grain quality, including traits specifying grain dimension and percentage of grains with chalkiness, quantitative genetic analysis was conducted in a population of 37 introgression lines (ILs) of indica elite variety Habataki in the background of japonica cultivar Sasanishiki across two different environments. The ILs showed transgressive segregation for all of the investigated traits, including percentage of grains with chalkiness, brown grain length, width, thickness, length/width ratio, length/thickness ratio, volume and 1,000-brown grain weight, the result indicated that these rice grain quality traits were polygenic phenomenon. Fifty-four QTLs were identified on eleven chromosomes, and 44 QTLs were associated with more than one trait, as a cause of the observed phenotypic correlations between different traits. Five stable QTLs, namely QPGWC.NH- 1.1, QPGWC.NH- 1.2, QGW.NH- 3.1, QLW.NH- 7.1 and QGV.NH- 8.2, were identified in this study. This study provides useful information for marker-aided improvement of grain quality (grain dimension and percentage of grains with chalkiness) in rice; moreover, ILs carrying these QTLs constitute good candidates for future fine mapping and positional cloning projects. [ABSTRACT FROM AUTHOR]

An extreme high temperature during grain filling is an important environmental factor that reduce the yield and quality of rice. In this study, we compared the grain appearance, composition and starch structure of four rice varieties response to high temperature during grain filling. The results obviously revealed that two indica AUS varieties Halwa and Jamir showed more tolerance to high temperature during grain filling than either the japonica Nipponbare or another AUS rice DJ24. The data showed that Halwa and Jamir presented less chalkiness, less grain weight loss, less change of endosperm components as well as starch structure than Nipponbare and DJ24 under high temperature treatment. Hence, the results implied that Halwa and Jamir might be useful targets to further identify genetic mechanism response to high temperature, at least during grain filling and endosperm development. Moreover, these AUS varieties have potential application value in further breeding of rice with good quality and heat tolerance. Image 1 • Jamir and Halwa are two AUS rice varieties that originated from low latitudes. • The yield and quality characteristics of Jamir and Halwa were hardly affected by high temperature. • The influences of high temperature on the starch fine structure of Jamir and Halwa were much slighter. [ABSTRACT FROM AUTHOR]

• Brown rice was milled into four layers to analyze endosperm composition. • Different compositions affected rice taste in different layers. • Apparent amylose content (AAC) and soluble sugar affected L3. • Protein content (PC) and amino acid affected L2. • Factors affecting rice taste ranked: AAC > soluble sugar > minerals > amino acids > PC. Clarifying the association of differences in endosperm biochemical composition with nutrient and edible quality can guide rice breeding and cultivation. In this study, very-low-amylose-content (LAC), Japanese good-taste (JTC), Northeast China good-taste (CTC), and Northeast China high-yield (CHC) cultivars were milled to obtain four layers (L1-L4) from outside-in, and then analyzed for apparent amylose content (AAC), protein content (PC), amino acids, soluble sugars, and minerals. The association of these compositions and Rapid-Visco analysis values with taste was also examined. LAC had low AAC, high amino acid and mineral content, and the highest taste value. Taste was significantly affected by AAC and soluble sugar in L3, and by PC in the L2 layer. High levels of amino acid in L2 and L3 improved the taste, as did Mg, P, and Ca in L1. On the whole, starch factors had the highest contribution to taste, followed by minerals, amino acids, and PC. [ABSTRACT FROM AUTHOR]

The japonica rice in Northeast China is famous because of its high quality. Eating and cooking qualities (ECQs) are the most important factors that determine cooked rice quality. However, the genetic basis of ECQ of japonica varieties in Northeast China needs further study. In this study, 200 japonica varieties that are widely distributed in Northeast China were collected to evaluate the physicochemical indices of grain ECQs. The distribution of each trait was concentrated without large variations. Correlation analysis indicated that gel consistency (GC) had a significantly negative correlation with gelatinization temperature (GT). By integrating various analyses including kinship calculation, principal component analysis (PCA), linkage disequilibrium (LD) analysis, and original parent investigation, we found that the japonica varieties in Northeast China exhibited a narrow genetic basis. An association study for grain ECQs was performed and eight quantitative trait loci (QTLs) were detected. ALK was the major locus that regulated GT and also significantly affecting GC. Through the linkage disequilibrium (LD) and expression pattern analysis, one possible candidate gene (LOC_Os02g29980) was predicted and required further research for validation. Additionally, a different allele of Wx was identified in the variety CH4126, and ALK was not fixed in these japonica varieties. These results further elucidate the genetic basis of ECQs of japonica varieties in Northeast China and provide local breeders some assistance for improving ECQs of rice grain in rice breeding. [ABSTRACT FROM AUTHOR]