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[学术文献 ] Slimming the Grain through Breeding Is a Practical Way to Reduce the Chalky Grain Rate of Middle-Season Hybrid Rice 进入全文
AGRONOMY-BASEL
The production of middle-season rice is an important part of agriculture in the Yangtze River basin of China. In recent years, the chalky grain rate of middle-season rice has decreased with the release of new cultivars. However, limited information is available on the factors responsible for this change in the chalky grain rate. This study evaluated the trends in the chalky grain rate and grain size traits of the new cultivars and the relationships between the chalky grain rate and grain size traits for middle-season hybrid rice in a province located in the middle reaches of the Yangtze River basin during 2006-2021. The results indicate that the recently reduced chalky grain rate of middle-season hybrid rice in the new cultivars is closely associated with a decrease in rice width, suggesting that it is feasible to reduce the chalky grain rate of middle-season hybrid rice by slimming the grain through breeding.
[学术文献 ] Genes and Their Molecular Functions Determining Seed Structure, Components, and Quality of Rice 进入全文
RICE
With the improvement of people's living standards and rice trade worldwide, the demand for high-quality rice is increasing. Therefore, breeding high quality rice is critical to meet the market demand. However, progress in improving rice grain quality lags far behind that of rice yield. This might be because of the complexity of rice grain quality research, and the lack of consensus definition and evaluation standards for high quality rice. In general, the main components of rice grain quality are milling quality (MQ), appearance quality (AQ), eating and cooking quality (ECQ), and nutritional quality (NQ). Importantly, all these quality traits are determined directly or indirectly by the structure and composition of the rice seeds. Structurally, rice seeds mainly comprise the spikelet hull, seed coat, aleurone layer, embryo, and endosperm. Among them, the size of spikelet hull is the key determinant of rice grain size, which usually affects rice AQ, MQ, and ECQ. The endosperm, mainly composed of starch and protein, is the major edible part of the rice seed. Therefore, the content, constitution, and physicochemical properties of starch and protein are crucial for multiple rice grain quality traits. Moreover, the other substances, such as lipids, minerals, vitamins, and phytochemicals, included in different parts of the rice seed, also contribute significantly to rice grain quality, especially the NQ. Rice seed growth and development are precisely controlled by many genes; therefore, cloning and dissecting these quality-related genes will enhance our knowledge of rice grain quality and will assist with the breeding of high quality rice. This review focuses on summarizing the recent progress on cloning key genes and their functions in regulating rice seed structure and composition, and their corresponding contributions to rice grain quality. This information will facilitate and advance future high quality rice breeding programs.
[学术文献 ] DNA Methylation Alterations and Their Association with High Temperature Tolerance in Rice Anthesis 进入全文
JOURNAL OF PLANT GROWTH REGULATION
DNA methylation is an important epigenetic mechanism involved in gene regulation under environmental stresses in plants. However, little information is available regarding its responses to high temperature (HT) and association with HT tolerance in rice. In this study, fourteen rice genotypes were classified into the susceptible, moderate, and tolerant groups by the high temperature susceptibility index (HTSI) after HT treatment. The changes of DNA methylation in rice anthesis under normal and HT30 conditions were investigated using methylation-sensitive amplified polymorphism31 (MSAP). The MSAP results showed that the DNA methylation level significantly increased in the susceptible rice group and decreased in the tolerant rice group under HT treatment, while no significant difference was observed in the moderate rice group. More hypomethylation events were detected in the tolerant rice group, while more hypermethylation was detected in the susceptible rice group. Forty-four differentially methylated epiloci (DME) were generated under both control and HT conditions, which can clearly distinguish the susceptible, moderate, and tolerant genotypes via PCoA analysis. Approximately 43.18% of DMEs were determined to be tolerance-associated epiloci (TAEs). 63.15% TAEs were sequenced and annotated into 12 genes. Quantitative RT-PCR analysis showed that 12 TAE genes were mainly upregulated in 14 rice genotypes, and their expression levels were related to the HT tolerance of rice. Here, DEGs, generated from a number of genotypes, indicate higher probabilities for association with stress tolerance. Overall, these results suggest that DNA methylation regulation might play a key role in adaptation to HT stress in rice.
[学术文献 ] Domain Unknown Function DUF1668-Containing Genes in Multiple Lineages Are Responsible for F-1 Pollen Sterility in Rice 进入全文
FRONTIERS IN PLANT SCIENCE
Postzygotic reproductive isolation maintains species integrity and uniformity and contributes to speciation by restricting the free gene flow between divergent species. In this study we identify causal genes of two Mendelian factors S22A and S22B on rice chromosome 2 inducing F-1 pollen sterility in hybrids between Oryza sativa japonica-type cultivar Taichung 65 (T65) and a wild relative of rice species Oryza glumaepatula. The causal gene of S22B in T65 encodes a protein containing DUF1668 and gametophytically expressed in the anthers, designated S22B_j. The O. glumaepatula allele S22B-g, allelic to S22B_j, possesses three non-synonymous substitutions and a 2-bp deletion, leading to a frameshifted translation at the S22B C-terminal region. Transcription level of S22B-j and/or S22B_g did not solely determine the fertility of pollen grains by genotypes at S22B. Western blotting of S22B found that one major band with approximately 46 kDa appeared only at the mature stage and was reduced on semi-sterile heterozygotes at S22B, implying that the 46 kDa band may associated in hybrid sterility. In addition, causal genes of S22A in T65 were found to be S22A_j1 and S22A_j3 encoding DUF1668-containing protein. The allele of a wild rice species Oryza meridionalis Ng at S22B, designated S22B_m, is a loss-of-function allele probably due to large deletion of the gene lacking DUF1668 domain and evolved from the different lineage of O. glumaepatula. Phylogenetic analysis of DUF1668 suggested that many gene duplications occurred before the divergence of current crops in Poaceae, and loss-of-function mutations of DUF1668-containing genes represent the candidate causal genetic events contributing to hybrid incompatibilities. The duplicated DUF1668-domain gene may provide genetic potential to induce hybrid incompatibility by consequent mutations after divergence.
[学术文献 ] Prediction of Heterosis for Agronomic Traits in Half-Diallel Cross of Rice (Oryza sativa L.) under Drought Stress Using Microsatellite Markers 进入全文
PLANTS-BASEL
Rice breeders are encouraged to classify potential F-1-hybrids without crossing all viable mixtures by testing depending on genetic distance due to lack of labor and time in yield trials. The goals of this research were to establish heterosis and investigate the relationship between genomic distance and agronomic attributes under drought. Half-diallel mating design, 28 F-1,(s) and 8 parents were evaluated under drought and genotyped using 11 microsatellite markers. In total, 39 alleles were detected. Results indicated that the greatest heterotic effects for grain yield were observed in Sakha 103 x Sakha 104 and GZ7576-10-3-2-1 x Giza 179, which gave 29.32-22.57% heterosis, respectively. Heterosis for grain yield in these crosses occurred as a rise in panicle weight, filled grains per panicle, low sterility and 100-grain weight. Correlations of marker-based genetic distance with mid-parent heterosis were positively and significantly correlated with sterility percentage (r = 0.390 *, p < 0.05). However, better-parent heterosis was positively and significantly correlated with sterility percentage (r = 0.352 *, p < 0.05) and grain yield per plant (r = 0.345 *, p < 0.05). Associations indicate that high grain yield and low sterility of rice crosses can be expected from microsatellite marker-defined distances of parents. This study indicated that genetic distance is very effective for heterosis prediction in breeding programs.
[学术文献 ] Effects of Fe-Zn-NA chelates priming on the vigour of aged hybrid rice seeds and the maintenance of priming benefits at different storage temperatures 进入全文
SEED SCIENCE AND TECHNOLOGY
The effects of seed priming with Fe-Zn-NA chelate (FeSO4+ZnSO4 +niacinamide) and the longevity of the beneficial priming effects were investigated for aged seeds of hybrid rice cv. Lingyouhuazhan (LYHZ) and cv. Longxiangyou 130 (LXY130). As compared with untreated and hydroprimed seeds, Fe-Zn-NA chelate priming significantly enhanced germination energy (GE), germination percentage (GP), germination index (GI), vigour index (VI) and normal seedling rate (NSR), and increased seedling shoot height (SH) and seedling dry weight (DW) in both cultivars. After priming with Fe-Zn-NA chelates, the GP of LYHZ was 96.0%, which was 12.7 and 12.0% higher than hydroprimed and non-primed seeds, respectively. Similarly, the GP of LXY130 was 89.5%, significantly higher than the hydroprimed and non-primed seeds (by 11.5 and 10.0%, respectively). When stored at 25 degrees C, the benefits of Fe-Zn-NA chelate priming on seed vigour and viability was maintained for three months; while after six months storage, the GP of LYHZ and LXY130 was only 48.0 and 34.0%, respectively, which was significantly lower than the non-primed seeds (84.0 and 71.1%). When stored at 15 or 5 degrees C for six months, the germination potential of Fe-Zn-NA chelate-primed seeds was still high. The GP of LYHZ and LXY130 seeds was 94.4% and 77.8%, respectively, after storage at 15 degrees C, and 97.8% and 85.6% after storage at 5 degrees C. In conclusion, the Fe-Zn-NA chelate priming was an effective method to improve the vigour and viability of hybrid rice aged seeds; however, the duration of beneficial priming effects needs to be determined according to the storage temperature.
