水稻大粒种质资源和遗传分析

谷粒重量是构成产量的三要素之一,对提高水稻产量具有重要意义.本文概述了国内外水稻大粒种质资源的现状,同时对粒重基因遗传分析的研究进展进行了综述.粒重是一个受多基因控制的数量性状,目前定位的粒重数量性状位点至少达89个、精细定位1个粒重基因gw3.1和1个长粒基因Lk-4（t）以及克隆1个粒重基因GS3,并在此基础上讨论了粒重在育种上的应用.     

高粱粒重遗传研究进展

高粱是世界第五大粮食作物,种植并培育高产的高粱品种对缓解世界粮食安全问题具有重要意义。粒重是构成产量的一个重要因素,增加粒重是提高高粱产量的重要途径。粒重是由数量性状基因控制的复杂性状,目前已有部分控制高粱粒重的QTLs(Quantitative trait loci,QTL)被定位,这些QTLs在高粱10条染色体上均有分布。对高粱粒重的遗传特点,粒重的影响因素及粒重QTL定位的研究进展进行了总结和概述,对已定位的高粱粒重QTLs进行了比较分析,查找了水稻和玉米中已克隆的粒重相关基因在高粱中的同源基因,并与高粱粒重QTLs定位区间进行了比较,以期为高粱粒重的分子标记辅助育种及高粱粒重主效QTLs的精细定位及克隆提供依据。     

水稻粒形遗传的研究进展

水稻（Oryza sativa）粒形性状包括粒长、粒宽、粒厚、粒重和长宽比等,是构成水稻产量的重要因素之一。因此,阐明水稻粒形遗传控制的机理,对提高水稻产量具有十分重要的意义。水稻粒形的遗传是多基因共同作用的数量性状遗传,相对于单一基因控制的性状,研究要相对复杂。该文综述了水稻粒形的遗传特点、QTL定位和基因克隆,并展望了粒形遗传的研究前景。     

水稻SL基因调控水稻的粒形

水稻产量和稻米品质的提高是水稻研究的中心问题。水稻产量主要取决于单株穗数、每穗粒数和粒重;粒重作为一个非常重要的产量性状,由粒长、粒宽和粒厚所决定。影响粒重和粒形的基因多为数量性状基因,精细定位并克隆到的较少。本研究中,我们克隆到一个影响粒形的基因SL,超表达（SL-OE）转基因植株表现出粒长增加、粒宽减小、叶宽减小的表型;同时,SL-RNAi的转基因植株呈现出粒长缩短、叶宽增加的表型。颖壳表面细胞在超表达转基因植株中伸长,而在RNAi转基因植株中缩短。叶片横向细胞数目在转基因植株中发生变化,推测乩基因可能与细胞分裂相关。SL-OE转基因植株中G嗽因被明显上调,说明盟基因可能通过调节GW2的表达对水稻粒宽造成影响。另外,观基因影响稻米的品质。     

编委推荐

正Molecular Plant|发现生长素调控水稻粒型的新机制水稻是世界重要的粮食作物,水稻的粒型是影响水稻产量的重要因素之一。到目前为止,已经分离出若干影响粒型的基因,而关于粒长和粒重的调控机制尚未完全清楚。中国农业科学院(深圳)农业基因组研究所钱前院士团队与浙江大学、内蒙古大学以及中国水稻研究所等多个团队合作,在9311和日本晴的重组自交系中鉴定出一个粒长和粒重数量性状位点qGL5,并将其精细定位到一个候选基因Os AUX3上(2021年6月27日在线发表,     

小麦粒重相关基因的遗传定位和分子标记辅助育种进展

粒重是小麦产量构成的三要素之一。该性状是受多基因控制的复杂数量性状,基因型和环境对其均有显著影响,但基因型是最为主要的决定因素。控制粒重及其构成要素的基因广泛分布在小麦3个基因组的各条染色体上,且已有多个可直接用于小麦粒重辅助选择的分子标记被开发。目前,国内外学者围绕粒重形成的遗传特征、基因定位、分子机理以及影响粒重高低的外界因素等进行了大量研究,并取得了一些重要的研究成果。本文综述了小麦粒重的构成因素及其影响因素,阐述了近年来粒重形成相关基因的遗传定位、克隆及其等位变异的挖掘,又系统总结了小麦粒重形成相关基因功能标记的开发及其分子标记辅助育种利用情况,同时展望了小麦粒重的下一步研究前景。     

水稻产量数量性状的遗传调控机制研究进展

粒重、每穗粒数和每株穗数是决定水稻产量的三大要素,也是水稻育种改良的重点．这些性状都是遗传复杂的数量性状．近十年来,水稻数量性状遗传学领域取得了突破性的进展,成功克隆了一批控制水稻产量性状的数量性状位点（QTL）．本文将简要介绍产量性状相关QTL的功能与作用机制．这些研究成果不仅有助于揭示产量性状形成的遗传基础,也将有力推动水稻分子设计育种的进程．     

水稻粒形性状的遗传及相关基因定位与克隆研究进展

作物育种的首要目标是提高产量。水稻粒形是与水稻产量性状直接相关,与品质性状存在着密切关系的数量性状,其评价指标主要是粒长、粒宽、粒厚、长/宽和长/厚。近年来,水稻粒形的数量遗传研究取得了重要进展,并成功定位克隆了一批控制水稻粒形的基因。文章综述了水稻粒形的经典遗传研究、QTL定位、粒形基因的克隆和功能分析以及在水稻超高产育种中的利用。     

水稻QTL定位研究进展

水稻的许多重要农艺性状均属于数量性状,研究水稻数量性状遗传对水稻育种具有十分重要的意义.近年来大量的研究揭示了水稻QTL的基本特征,剖析了重要农艺性状的遗传基础,给水稻遗传改良带来了新策略,不断深入的研究已经完成了水稻特定数量基因的精细定位和克隆,到目前为止已经有一万多个水稻QTL进行了定位,其中有19个进行了克隆,这对水稻育种具有十分重要的意义.本文主要综述了QTL定位的理论基础,水稻QTL定位的研究进展,并对水稻QTL研究的趋势进行了展望.     

水稻产量相关QTL研究现状

产量是最为复杂的数量性状,对它的遗传机理了解甚微。近15年来,许多学者利用随机分离群体定位了许多影响水稻产量及其组分的QTL,即以QTL定位的方法对产量潜力进行遗传剖析。试验证明上位性效应对产量及其组分性状遗传变异起着重要作用,但目前大多数QTL研究仍侧重于发掘和克隆单个主效QTL,然而对单一基因／QTL的深入了解还不足以诠释复杂性状遗传基础的全貌,还没有为育种家提供足够的可应用于分子标记辅助育种的遗传信息并用于提高水稻产量。笔者认为今后的数量性状研究尚需加强复杂性状QTL遗传网络的发掘,在改良水稻品种性状的同时发展并完善QTL研究。     

Fine mapping of a grain-weight quantitative trait locus in the pericentromeric region of rice chromosome 3

As the basis for fine mapping of a grain-weight QTL, gw3.1, a set of near isogenic lines (NILs), was developed from an Oryza sativa, cv. Jefferson x O. rufipogon (IRGC105491) population based on five generations of backcrossing and seven generations of selfing. Despite the use of an interspecific cross for mapping and the pericentromeric location of the QTL, we observed no suppression of recombination and have been able to narrow down the location of the gene underlying this QTL to a 93.8-kb region. The locus was associated with transgressive variation for grain size and grain weight in this population and features prominently in many other inter- and intraspecific crosses of rice. The phenotype was difficult to evaluate due to the large amount of variance in size and weight among grains on a panicle and between grains on primary and secondary panicles, underscoring the value of using multiple approaches to phenotyping, including extreme sampling and NIL group-mean comparisons. The fact that a QTL for kernel size has also been identified in a homeologous region of maize chromosome 1 suggests that this locus, in which the dominant O. rufipogon allele confers small seed size, may be associated with domestication in cereals.     

Spatial and temporal expression modes of MicroRNAs in an elite rice hybrid and its parental lines

Heterosis is a commonly observed phenomenon in nature and refers to the superior performance of hybrids relative to both parents. The molecular mechanisms of heterosis are mostly unknown. Quantitative trait locus (QTL) mapping has been used to explain the genetic basis of heterosis, and large amounts of QTLs have been mapped for various agronomic traits, but the nature of QTL contributing to heterosis is still enigmatic. MicroRNAs (miRNAs) are master regulators in the processes of plant development and trait performance, and many miRNAs are predicted to reside in QTL intervals. We analyzed the expression modes of miRNAs, which were picked up from miRNA databases and chosen from those predicted from QTL intervals by bioinformatic approaches, in different organs at developmental stages of an elite rice hybrid and its parents. All possible modes of action for miRNA expression were detected, but most miRNAs showed nonadditive mode, and different stages and distinct organs displayed different patterns of miRNA expression. A large proportion of miRNAs were not detected for expression in leaves but expressed in the culms and roots of the hybrid at tillering stage. MiRNAs from grain-weight QTL intervals have multiple effects on grain development. Together, our results reveal that miRNAs, especially those from QTL intervals, play roles in heterotic performance in this elite rice hybrid, our results also shade new light on understanding the molecular mechanisms of heterosis.     

Origin and Genetic Diversity of Aromatic Rice Varieties, Molecular Breeding and Chemical and Genetic Basis of Rice Aroma

Aroma is an important quality attribute of rice and is a key determinant of its market value. Among the different groups of aromatic rice varieties ‘Basmati’ from the Indian subcontinent and ‘Jasmine’ from Thailand occupy prime position in the international market. In addition, there are a large number of premium short-grain aromatic rice varieties cultivated by farmers in India and South-East Asia that have not been fully commercially utilised as yet. The origin and evolution of aromatic rice varieties is being unravelled by application of genomic tools. The common alleles of aroma gene seem to have their origin in the aromatic group of rice varieties native to the Sub-Himalayan region. Of more than two hundred volatile compounds present in the rice grain, 2-acetyl-l-pyrolline (2-AP) is considered as the key aroma compound present in almost all the aromatic rice varieties. However, there is significant variation in the type and intensity of aroma in the different groups of aromatic rice varieties suggesting involvement of additional chemical compounds in varying proportions. Studies have been undertaken to understand the genetics of rice aroma and to map the genes or quantitative trait loci (QTL) controlling aroma expression. Of the three mapped aroma QTL, qaro8.1 located on rice chromosome S is the most significant and it represents a non-functional allele of BADH2 gene coding for enzyme betaine aldehyde dehydrogenase. Functional allele of the BADH2 gene makes rice non-aromatic. Similarly, specific alleles of BADH1 gene located on rice chromosome 4 within the aroma QTL qaro4.1 show association with the aromatic rice varieties. The gene underlying QTL qaro3.1 on chromosome 3 has not yet been deciphered. Functional molecular markers have been developed for the major aroma QTL on chromosome S and marker-assisted breeding for high yielding aromatic rice varieties is now a reality. To safeguard the reputation of Basmati rice an international code of practice has been developed where DNA markers help check the purity of commercial samples. There is need to use advanced genomic and metabolomic approaches to further study the minor genes controlling rice aroma and understand the variation in type, intensity and stability of rice aroma. It is also required to improve the production and marketing of short grain aromatic rice varieties.     

Expression of expansin genes is correlated with growth in deepwater rice.

Expansins are a family of proteins that catalyze long-term extension of isolated cell walls. Previously, two expansin proteins have been isolated from internodes of deepwater rice, and three rice expansin genes, Os-EXP1, Os-EXP2, and Os-EXP3, have been identified. We report here on the identification of a fourth rice expansin gene, Os-EXP4, and on the expression pattern of the rice expansin gene family in deepwater rice. Rice expansin genes show organ-specific differential expression in the coleoptile, root, leaf, and internode. In these organs, there is increased expression of Os-EXP1, Os-EXP3, and Os-EXP4 in developmental regions where elongation occurs. This pattern of gene expression is also correlated with acid-induced in vitro cell wall extensibility. Submergence and treatment with gibberellin, both of which promote rapid internodal elongation, induced accumulation of Os-EXP4 mRNA before the rate of growth started to increase. Our results indicate that the expression of expansin genes in deepwater rice is differentially regulated by developmental, hormonal, and environmental signals and is correlated with cell elongation.     

Molecular evolution of the rice blast resistance gene Pi-ta in invasive weedy rice in the USA

The Pi-ta gene in rice has been effectively used to control rice blast disease caused by Magnaporthe oryzae worldwide. Despite a number of studies that reported the Pi-ta gene in domesticated rice and wild species, little is known about how the Pi-ta gene has evolved in US weedy rice, a major weed of rice. To investigate the genome organization of the Pi-ta gene in weedy rice and its relationship to gene flow between cultivated and weedy rice in the US, we analyzed nucleotide sequence variation at the Pi-ta gene and its surrounding 2 Mb region in 156 weedy, domesticated and wild rice relatives. We found that the region at and around the Pi-ta gene shows very low genetic diversity in US weedy rice. The patterns of molecular diversity in weeds are more similar to cultivated rice (indica and aus), which have never been cultivated in the US, rather than the wild rice species, Oryza rufipogon. In addition, the resistant Pi-ta allele (Pi-ta) found in the majority of US weedy rice belongs to the weedy group strawhull awnless (SH), suggesting a single source of origin for Pi-ta. Weeds with Pi-ta were resistant to two M. oryzae races, IC17 and IB49, except for three accessions, suggesting that component(s) required for the Pi-ta mediated resistance may be missing in these accessions. Signatures of flanking sequences of the Pi-ta gene and SSR markers on chromosome 12 suggest that the susceptible pi-ta allele (pi-ta), not Pi-ta, has been introgressed from cultivated to weedy rice by out-crossing.     

mRNA accumulation and promoter activity of the gene coding for a hydroxyproline-rich glycoprotein in Oryza sativa

The accumulation of the mRNA corresponding to the gene coding for a hydroxyproline-rich glycoprotein has been studies in rice. The patterns of gene expression obtained are similar to those observed in maize in regions rich in dividing cells such as the meristematic zones of roots. However, the gene does not seem to be induced by wounding as it is the case in maize. This effect is correlated with the absence of sequences present in the promoter of the maize gene and that have been described as responsible for ethylene induction on other plant systems. Instead, the promoter has a sequence that corresponds to abscisic acid-responsive elements and, in fact, HRGP mRNA levels can be two-fold increased in rice leaves by ABA. The genes coding for homologous proteins in two cereal species such as maize and rice appear, therefore, to have distinct mechanisms of gene regulation.     

The gene for fragrance in rice

The flavour or fragrance of basmati and jasmine rice is associated with the presence of 2-acetyl-1-pyrroline. A recessive gene (fgr) on chromosome 8 of rice has been linked to this important trait. Here, we show that a gene with homology to the gene that encodes betaine aldehyde dehydrogenase (BAD) has significant polymorphisms in the coding region of fragrant genotypes relative to non-fragrant genotypes. The accumulation of 2-acetyl-1-pyrroline in fragrant rice genotypes may be explained by the presence of mutations resulting in a loss of function of the fgr gene product. The allele in fragrant genotypes has a mutation introducing a stop codon upstream of key amino acid sequences conserved in other BADs. The fgr gene corresponds to the gene encoding BAD2 in rice, while BAD1 is encoded by a gene on chromosome 4. BAD has been linked to stress tolerance in plants. However, the apparent loss of function of BAD2 does not seem to limit the growth of fragrant rice genotypes. Fragrance in domesticated rice has apparently originated from a common ancestor and may have evolved in a genetically isolated population, or may be the outcome of a separate domestication event. This is an example of effective human selection for a recessive trait during domestication.