Anatomy of Nodal Roots in Tropical Upland and Lowland Rice Varieties

abstract

Nodal root anatomy was compared among twelve upland and lowland rice (Oryza sative L.) varieties with tropical origin which were grown in hydroponic culture and under field conditions. The traditional upland japonica varieties showed the largest diameter of root, stele, and xylem vessel followed by modern upland varieties. There was a clear varietal difference in the ratio of stele to root diameter, which was associated with the genetic group rather than with the ecosystems. The japonica varieties had a significantly larger stele diameter relative to the root diameter than indica and aus varieties. The indica and aus varieties displayed more xylem vessels per unit area of stele than the japonica varieties, but the diameter of xylem vessel was smaller. Equivalent xylem vessel diameter (De) was more dependent on the number of xylem in the indica varieties than in the japonica varieties. Distinctly different types of sclerenchyma anatomy were identified among the varieties. The development of sclerenchyma was classified into four different types based on thickening of cell wall in the outer cortical parenchyma and the number of sclerenchymatous cell layers. Like the xylem anatomy, the varietal differences in sclerenchyma development were more associated with genetic group rather than the ecotype. The japonica varieties had higher frequency of the types which have a doubled cell layer in sclerenchyma with thick cell wall than indica and aus. The difference among the genetic groups was nearly consistent across growing conditions, aerobic and submerged soils. These results indicated that sclerenchyma development is controlled by a genetic factor.     

Genetic Diversity of Rice Landraces from Lowland and Upland Accessions of China

Genetic diversity of rice landraces from lowland and upland accessions of China was investigated using 66 polymorphic simple sequence repeat (SSR) markers.The total number of alleles detected from all 324 tested accessions was 555 with an average allele number (Na) of 8.409 per locus,the average effective number of alleles (Ne) of 3.574 and the average Shannon’s information index (I) of 1.378.The genetic diversity was higher for the indica landraces compared to the japonica landraces,and the upland landraces were more genetically diverse than the lowland landraces.The SSR markers,RM72,RM232,RM219,RM241,RM224 and RM3 showed the highest rates of polymorphism and these SSR markers were suitable to assess the genetic diversity of rice germplasm resources.A dendrogram of 324 accessions of lowland and upland landraces showed that all rice accessions were mainly subdivided into two groups,japonica and indica,with some being intermediate.The distribution of lowland and upland landraces among the japonica and indica rice groups was distinct,with obvious differentiation between the lowland and upland landraces in japonica rice,but no such clear distinction in indica rice.     

两系杂交稻优势生态型的初步研究

研究了培矮 64S和N4 2 2S与粳亚种中的东北粳、华北粳、日韩粳、云贵粳、非洲粳、美国稻及籼亚种中的云贵籼、太湖籼、华中籼和Aus稻的杂种F1的产量及产量构成因素的杂种优势 ,初步确定美国稻、非洲粳、云贵粳以及华北粳中的改良品种是粳稻的优势生态型 ,太湖籼与云贵籼是籼稻的优势生态型。对籼粳优势生态型的产量优势进行比较发现 ,N4 2 2S/太湖籼低于N4 2 2S/美国稻 ,但与N4 2 2S/非洲粳和N4 2 2S/云贵粳相当 ;培矮64S与粳稻优势生态型的优势强于与籼稻优势生态型的优势。两个不育系的优势比较表明 ,培矮 64S与各生态型的杂种优势强于N4 2 2S与各生态型的杂种优势     

利用微卫星标记分析浙江省近年来主要水稻品种的遗传多样性

 利用12个DNA微卫星标记分析了浙江省近年来主要的44个常规水稻品种和54个杂交水稻组合,共检测到等位基因68个,每个标记2~10个;带型数共127种,每个标记3~18种;平均多态性频率0.752,变幅为0.567~0905。常规品种和杂交组合均表现为亚种间遗传差异明显、亚种内遗传差异较小,籼型遗传多样性高于粳型。平均遗传相似系数,常规品种籼型为0.672,粳型为0.711,籼粳间为0.103,杂交组合籼型为0.636,粳型为0.669,籼粳间为0.343。聚类分析显示,以遗传相似系数0.618为阈值将常规品种分成6类,以0.601为阈值将杂交组合分成7类,且多数同类型品种或组合聚为同一类。     

两系杂交稻优势生态型的初步研究

研究了培矮６４Ｓ和Ｎ４２２Ｓ与粳亚种中的东北粳、华北粳、日韩粳、云贵粳、非洲粳、美国稻及籼亚种中的云贵籼、太湖籼、华中籼和Ａｕｓ稻的杂种Ｆ１的产量及产量构成因素的杂种优势,初步确定美国稻、非洲粳、云贵粳以及华北粳中的改良品种是粳稻的优势生态型,太湖籼与云贵籼是籼稻的优势生态型。对籼粳优势生态型的产量优势进行比较发现,Ｎ４２２Ｓ／太湖籼低于Ｎ４２２Ｓ／美国稻,但与Ｎ４２２Ｓ／非洲粳和Ｎ４２２Ｓ／云贵粳相当;培矮６４Ｓ与粳稻优势生态型的优势强于与籼稻优势生态型的优势。两个不育系的优势比较表明,培矮６４Ｓ与各生态型的杂种优势强于Ｎ４２２Ｓ与各生态型的杂种优势。     

我国常规稻主栽品种的遗传变异分析

 采用40个SSR标记,分析了329份我国近50年来常规稻主栽品种的遗传变异。结果显示,39个SSR标记具有多态性,在多态性位点共检测到223个等位基因,每个位点2～11个,平均57个;平均Nei基因多样性指数（He）为0632。籼粳亚种间的SSR变异差异明显,籼稻平均等位基因数（Na）和Nei基因多样性指数（Na = 54,He = 0440）均高于粳稻品种（Na = 44,He = 0397）。Nei遗传相似系数表明总体样本具有较小的遗传相似度（I = 0366）,而骨干亲本具有较高的遗传相似度（籼:I = 0590;粳:I = 0590）。这导致了籼粳亚种内较高的遗传一致性（籼:I = 0558;粳:I = 0600）。早、中、晚稻各类型遗传相似度差异明显,晚籼和早粳类型具有较高的遗传变异。籼粳稻品种尤其是粳稻的聚类结果显示出较强的季节型和地域特征。这些均提示育种家应选择更广泛的亲本源以拓宽选育品种的遗传基础。     

A Comparative Study of SSR Diversity in Chinese Major Rice Varieties Planted in 1950s and in the Recent Ten Years （1995-2004）

Forty pairs of SSR markers were used to compare the genetic diversity changes in 151 Chinese major rice varieties planted in 1950s and in the recent ten years. Of 40 SSR loci, 39 were found to be polymorphic while one locus (RM479) monomorphic. A total of 213 alleles were identified from the 39 polymorphic loci. The average number of alleles per locus (Na) was of 5.5, ranging from 2 to 11. Nei’s gene diversity index (He) varied drastically among loci from 0.309 at RM174 to 0.869 at RM418, with an average value of 0.649. There existed significant difference in SSR allelic diversity between indica and japonica subspecies, and indica had more variation than japonica both in Na and He. By comparison with the genetic changes in Na and He, it was revealed that the varieties planted in 1950s had more alleles and higher He than those in the recent ten years both for indica and japonica rices. The difference between two subspecies for Na was significant in a tendency over time (indica: z = 2.677, P = 0.007; japonica: z = 3.441, P = 0.001), but not significant for He (indica: z = 1.471, P = 0.141; japonica: z = 1.932, P = 0.053). Analysis of molecular variance (AMOVA) indicated that there existed significant difference (P < 0.05) in genetic variation between the two periods, of which more genetic variation was contributed by indica (Fst = 0.050) and japonica (Fst = 0.082) subsets. Using locus-by-locus AMOVA procedure, significant genetic differentiations were observed in 13 loci (RM21, RM128, RM147, RM169, RM190, RM221, RM231, RM251, RM253, RM317, RM341, RM418, and RM478) for indica varieties and 11 loci (RM101, RM135, RM152, RM159, RM169, RM190, RM251, RM253, RM311, RM418, and RM478) for japonica ones between the two periods. It was found some alleles had been lost in current major rice varieties as comparing with those in 1950s. Therefore, it should be necessary to exploit more alien elite genetic resources for extension of genetic background in current rice breeding program.     

云南地方稻种Wx基因第一内含子供体+1位碱基变异与直链淀粉含量的关系

应用PCR一步法对来自云南省14个地州、55个市/县的220个籼、粳地方稻种Wx基因第一内含子供体+1位碱基G/T进行了检测,同时用PCR Acc I酶切法对其中的101份进行验证,结果表明两种方法检测结果一致。根据G/T碱基将220个供试材料分为GG、TT两种基因型。云南地方稻种以GG型占优势,有164个,占74.5%;TT型有56个,占255%;籼稻中80.5%属GG型,粳稻中67.0%属GG型。GG型直链淀粉含量较高,平均18.97%,TT型较低,均低于16%, GG、TT基因型之间的平均直链淀粉含量差异极显著。G/T与直链淀粉含量存在密切的联系,其相关系数为0733**。GG型品种中有33个直链淀粉含量较低（3.91%～15.93%）,多数为来源于云南西南部傣族地区的品种。籼稻中的GG型或TT型品种与粳稻中的GG型或TT型品种间平均直链淀粉含量无显著差异,表明GG/TT基因型在籼粳不同遗传背景下直链淀粉表达无显著差异。     

Relationship Between the First Base of the Donor Splice Site of Waxy Gene Intron 1 and Amylose Content in Yunnan Indigenous Rice Varieties

There exists a single nucleotide polymorphism, G or T, at the first base of the donor splice site of waxy gene intron 1 in rice. In order to study the relationship between the first base of the donor splice site of waxy gene intron 1 and amylose content in rice, the one-step PCR method was used to determine whether it is G or T in 220 Yunnan indigenous rice varieties from 14 districts, 55 towns/counties of Yunnan Province, and 101 varieties of which were validated by the PCR-Acc I method. According to the G/T polymorphism, 164 rice varieties showed GG-genotype, while the other 56 fell into TT-genotype, accounting for 74.5% and 25.5% of all the test varieties, respectively. When all the rice varieties were divided into indica and japonica subspecies, it was found that 80.5% of indica rice and 67.0% of japonica rice belonged to GG-genotype. The rice varieties with GG-genotype had significantly higher amylose content (18.95% on average) than those with TT-genotype (all below 16%), but 33 rice varieties with GG-genotype still had low amylose content ranging from 3.91% to 15.93%, and most of them came from the Dai minority area in the Southwest of Yunnan Province. However, there was no significant difference in the mean amylose content of the same GG or TT genotypes between indica and japonica rice, suggesting that different genetic backgrounds, indica or japonica, had no effect on amylose content. The coefficient of correlation between the genotype and amylose content was 0.733 (P<0.01).     

水稻籼粳特异性RFLP标记及广亲和品种亲缘关系分析

 应用160个RFLP标记分析了21个水稻广亲和品种6个籼粳测验种，发现其中68个标记可以区分籼粳测验种。21个广亲和品种根据与籼粳测验和共有片段比率的大小 可以分为籼，粳和籼粳中间型三类。68个标记在15个籼粳品种中进一步筛选，得到24个籼粳特异性RFLP标记。它们在亚种内杂交带型相同而亚种产不一样。其中RG358、G318为籼稻专一性探针，在粳稻中表现为零等位。以此24个探针为基础构建了广亲和品品种亲缘关系的树状图。讨论了籼粳特异性RFLP标记在水稻遗传育种实践中的应用。     

我国水稻主栽品种SSR多样性的比较分析

采用40个SSR标记,比较分析了151份20世纪50年代(78份）和近10年（73份）我国常规稻主栽品种的遗传差异,发现有39个标记具有多态性,多态性位点共检测到213个等位基因,每个位点2～11个,平均5.5个;平均Nei基因多样性指数(He)为0.649,范围在0.309（RM174）～0.869（RM418）。籼粳亚种间SSR多样性差异明显,籼稻平均等位基因数（Na）和Nei基因多样性指数（Na = 4.4,He = 0.458）均高于粳稻品种（Na = 4.0,He = 0.395）。比较了78份20世纪50年代与73份近10年水稻主栽品种的遗传多样性,籼、粳亚种表现出相近的变化趋势,即Nei多样性指数和等位基因数20世纪50年代主栽品种高于近10年的。虽然Nei基因多样性指数的变化并不显著（籼稻：z= 1.471,P=0.141;粳稻：z= 1.932,P=0.053）,但等位基因数目的变化达到显著水平（籼稻：z= 2.677,P=0.007;粳稻：z= 3.441,P=0.001）。分子方差分析(AMOVA)表明,遗传变异绝大部分存在于两时期内,尽管时期间平均贡献的遗传变异仅占1.9％,但仍然达到5％的显著水平;籼、粳亚种两时期间平均贡献的遗传变异高于整个分析样本,分别为5.0％和8.2％;籼、粳亚种不同位点的遗传分化程度也各不相同,籼稻和粳稻品种分别有13个（占33.3％）和11个（占28.2％）SSR位点的等位基因在两时期间差异显著,而其余位点的遗传变异则是因时期内品种间的差异引起的。研究表明近10年我国常规稻主栽品种丢失了一部分等位基因,水稻育种仍应加强更广泛的种质亲本的选择。     

Four Decades of Breeding for Varietal Improvement of Irrigated Lowland Rice in the International Rice Research Institute

Abstract

Since the establishment of the International Rice Research Institute (IRRI) in 1960, IRRI’s breeding effort in varietal improvement for irrigated lowland has passed four decades. Breeding of semi-dwarf rice varieties such as IR8 at IRRI during first decade from 1960 to 1969 resulted in quantum leaps in yield potential, which marked the green revolution in Asia. During the second decade from 1970 to 1979, the primary emphasis of rice improvement has been directed towards incorporation of multiple disease and insect resistance and shortening of growth duration. Grain quality was the main target of crop improvement at IRRI during the third decade from 1980 to 1989. The fourth decade from 1990 to 1999 and beyond was focused again on the improvement of yield potential by developing hybrid rice and new plant type. Up to 1999, 46 indica inbred varieties and 2 indica/indica hybrid rice varieties were developed by IRRI and released in the Philippines for the irrigated lowland rice systems. Large-scale adoption of these improved varieties under modern crop management practices has resulted in a dramatic increase in rice production in major rice-growing countries. The hybrid varieties between indicas increased yield potential by 9% under the tropical conditions. New plant type (NPT) breeding has not yet resulted in an increase in yield potential. The second generation NPT developed by crossing tropical japonica with indica has demonstrated some promising results in terms of improvements in yield potential, disease and insect resistance, and grain quality.     

利用SSR分子标记分析云南陆稻品种遗传多样性

 利用24对SSR引物对云南131个陆稻品种进行遗传多样性分析。共检测到195个等位基因。每个位点的等位基因数平均为8.125个,范围在5(RM55)～13(RM218、RM241)之间;平均表观杂合度为0.0014,平均期望杂合度为0.6545;平均Shannon Weaver指数(I)为1.381;Nei基因多样性指数(H)平均为0.6543,变幅为0.2073(RM235)～0.8689(RM218)。不同地区间陆稻种质资源遗传多样性比较分析表明,滇西南和滇南地区存在丰富的遗传变异,是云南陆稻品种遗传多样性的分布中心。藏缅语族和孟 高棉语族所种植的陆稻品种遗传多样性最丰富。AMOVA分析表明陆稻的遗传变异主要存在于地区内品种间(82%),只有3%遗传变异存在于地区间,品种内的遗传变异占15%。聚类分析显示Nei遗传相似系数为0.22时,云南陆稻品种分为籼粳两个类群,主坐标分析与UPGMA聚类结果基本吻合,并将类群Ⅳ的4个偏籼品种从粳稻类群中重新划归到籼稻类群中,校正了UPGMA聚类的误差,但是不能区分地理组。     

部分栽培稻和野生稻种子谷蛋白的电泳分析

 供试的不同属、不同种及不同生态型的水稻材料的种子各蛋白经SDS-PAGE电泳后可分辨为3类多肽，分子量分别为l8～23 kDa．30～36 kDa和49～100 kDa。不同属的材料各蛋白带型明显不同； 同属内基因组相同或相近种的各蛋白有特征多肽，AA基因组的有约Mt.50 kDa的多肽2～3条，CCDD基因组的有约Mt.23 kDa的多肽一条；籼型和粳型稻间带型存在差异，而爪哇稻、粳稻、籼稻间，前二者略近，并以粳型陆稻与爪哇稻最近似。同一生态型的各品种，除细弱带偶尔有差异外，带型基本一致。由此可见，水稻各蛋白电泳分析作为方法之一， 对于属间和稻属内各种及种内分类是有意义的。     

Genetic Structure and Indica/Japonica Component Changes in Major Inbred Rice Varieties in China

We used 39 SSR markers to analyze the genetic structure of 304 major Chinese inbred rice varieties, and to compare changes in the indica or japonica components in these varieties that have been widely cultivated from the 1950s to the 1990s in China. The genetic structure analysis showed that these rice varieties were distinctly divided into two populations, indica and japonica. The sub-structure of indica varieties was more complex than that of japonica ones. Among the various lines, late-season indica and early season japonica varieties had simpler genetic backgrounds. The seasonal ecotypes were not quite consistent with the subtypes of genetic structure. Twelve SSR loci with specific differentiation between indica and japonica were used to calculate the indica/japonica components. The differences in indica/japonica components among the five decades were not significant, except for late-season indica varieties in the 1990s, which had a significantly higher japonica component. These results will help to understand the genetic structure of the major Chinese inbred rice varieties and will be useful for indica-japonica hybrid breeding in China.     

中国常规稻主栽品种的遗传结构及籼粳组分变化

 采用SSR标记分析了304份我国20世纪50-90年代生产上广泛应用的常规稻主栽品种的遗传结构及不同时期籼粳组分的变化。结果显示,我国常规稻主栽品种可明显分为籼、粳两类,籼稻的亚遗传结构比粳稻更为复杂,但晚籼和早粳类型的遗传背景略为单一。早、中、晚各季节类型与遗传结构的分型结果符合度较低。利用12个籼粳分化特异的SSR位点分析各品种的籼粳组分,发现20世纪90年代晚籼类型的粳型组分明显增加,而其他类型不同时期间籼粳组分的差异较小。研究结果对了解我国常规稻品种的遗传结构以及籼粳交育种具有一定的意义。     

水稻广亲和系的选育

水稻广亲和基因的发现及其遗传研究 ,揭开了籼粳稻亚种间杂种一代半不育现象的遗传本质 ,为利用水稻亚种间杂种优势指明了方向。但是 ,已知的广亲和材料 ,绝大多数为古老的农家品种 ,农艺性状不良 ,如植株太高 ,株叶形披散和生育期很长等 ;不能直接作为选配优良组合的亲本加以利用。因此 ,培育具有优良农艺性状和经济性状、可供实用的水稻广亲和系就显得非常重要 ,这是开展亚种间杂种优势育种的首要任务之一。普通栽培稻有籼稻、粳稻和爪哇稻三个亚种 ,所以亚种间的杂交可分为籼粳交、籼爪交和粳爪交三种形式。初步研究表明 ,水稻杂种优势强弱的程度 ,具有籼粳交 >籼爪交 >粳爪交 >籼籼交 >粳粳交的一般趋势。也就是说 ,亚种间的杂种优势一般要强于品种间的。为了能充分利用各种形式的亚种间杂种优势 ,提高育成强优组合的几率 ,就有必要建立籼、粳、爪三个亚种类型的优良广亲和系。我们在以前工作的基础上 ,近年来开展了水稻广亲和系选育的研究 ,已取得一些进展和结果 ,育成了粳型广亲和系培C3 11,爪哇型广亲和系轮回 4 2 2 ,籼型广亲和系培矮 64以及广亲和光敏核不育系培矮 64S。     

基于SSILP、InDel和SSR标记的杂草稻籼粳分类

 采用40对SSILP、30对InDel和43对SSR标记对来自斯里兰卡的28份杂草稻和14栽培稻,来自国内外的9份籼型栽培稻、7份粳型栽培稻和4份代表性杂草稻进行遗传多样性分析。SSILP、InDel和SSR标记分别检测到84、61和213个等位基因,其平均多态性信息含量(PIC)分别为0.257、0.255和0.543。聚类分析显示供试的42份斯里兰卡杂草稻和栽培稻均为籼型。SSILP与InDel标记的相关性很高（r=0.989）,而它们与SSR标记相关性较低（0.812和0.808）。结果表明,SSILP和InDel标记可高效鉴别各类稻种资源的籼粳属性,而SSR标记更适用于亚种内的分类。     

中国栽培稻等位酶的遗传结构及地理分布

对我国6330份栽培稻品种进行了5种等位酶12个位点的遗传结构分析,共检测到53个等位基因,平均等位基因数为4.41,多样性指数值为0.269,表明中国栽培稻具有丰富的等位酶遗传多样性。地方农家品种和现代育成品种遗传多样性指数差异不大,但现代育成品种等位基因较少,共有13个稀有等位基因仅存在于地方农家品种中。比较我国六大生态稻区的等位酶分布,发现西南稻区的等位酶基因最为丰富,为我国稻种资源的多样性中心,但华北和华中稻区在某些等位酶基因上的多样性以及某些稀有等位基因的存在暗示着淮河流域和长江流域可能与栽培稻的起源有关。利用等位基因聚类分析基本可以把地方农家品种分成两大类,分别是籼稻和粳稻,籼稻的遗传多样性大于粳稻。籼粳稻在等位酶位点上的差异不仅表现为单个等位基因形式和频率的不同,还表现为多位点非随机组合的遗传差异。     

Conservation and utilization of rice genetic resources in China

Rice genetic resources presents variably in China. There are land races and wild species. cultivated lowland rice and upland rice, indica (Hsien) and japonica (Keng) riee. early, middle, and late rice as well as glutinous and non-glutinous rice. Up to February 2000, a total of 76, 646 rice accessions were catalogued,and 67. 444 base accessions were stored in the National Crop Gene Bank in the Institute of Crop Genetic Resources (ICGR) of the Chinese Academy of Agricultural Sciences, Beijing, China (Table 1). About 35,000 rice duplicates were stored in China National Rice Research Institute(CNRRI), Hangzhou, Zhejiang Province. China.