Published March, 2002
NI ET AL.:EVALUATION OF GENETIC DIVERSITY IN RICE SUBSPECIES601 Hornes,A.Frijters,J.Pot,J.Peleman,M.Kuiper,and M.Zabeau.Xu,R.Q.,N.Tomooka,and D.A.Vaughan.2000.AFLP markers for
characterizing the Azuki bean complex.Crop Sci.40:808–815.
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Mao.1997.POPGENE,the user-friendly shareware for population Wachira,F.N.,R.Waugh,C.A.Hackett,and W.Powell.1995.Detec-
tion of genetic diversity in tea(Camellia sinensis)using RAPD genetics analysis.Molecular Biology and Biotechnology Center, markers.Genome38:201–210.
University of Alberta,Canada.(http://www.ualberta.ca/?fyeh;veri-Wight,W.1962.Tea classification revised.Curr.Sci.31:298–299.fied September27,2001).
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by RFLP analysis.Theor.Appl.Genet.83:495–499.
Evaluation of Genetic Diversity in Rice Subspecies Using Microsatellite Markers
Junjian Ni,Peter M.Colowit,and David J.Mackill*
ABSTRACT molecular markers can reveal differences among acces-
sions at the DNA level and thus provide a more direct, Molecular markers are useful tools for evaluating genetic diversity
reliable,and efficient tool for germplasm conservation and determining cultivar identity.The purpose of this study was to
evaluate the genetic diversity within a diverse collection of rice(Oryza and management.
sativa L.)accessions,and to determine differences in the patterns of Several types of molecular markers are available for diversity within the two rice subspecies indica and japonica.Thirty-evaluating the extent of genetic variation in rice.These eight rice cultivars of particular interest to U.S.breeding programs include restriction fragment length polymorphism and two wild species accessions(O.rufipogon Griffithand O.nivara(RFLP)(Botstein et al.,1980),random amplified poly-Sharma et Shastry)were evaluated by means of111microsatellite morphic DNA(RAPD)(Welsh and McClelland,1990; markers distributed over the whole rice genome.A total of753alleles Williams et al.,1990),amplified fragment length poly-were detected,and the number of alleles per marker ranged from1
morphism(AFLP)(Vos et al.,1995),and microsatellite to17,with an average of6.8.A positive correlation was found between
or simple sequence repeat(SSR)(Tautz,1989).Of the number of alleles per locus and the maximum number of repeats
these,RFLP and microsatellites are codominant mark-within a microsatellite https://www.doczj.com/doc/915491003.html,pared to indica cultivars,the
japonica group showed significantly higher genetic diversity on chro-ers and their map positions on the rice genome are well mosomes6and7,and considerably lower diversity on chromosome known,while RAPD and AFLP markers involve the 2.All rice cultivars and lines could be uniquely distinguished,and use of random,largely dominant markers.Microsatel-the resulting groups corresponded exactly to the indica and japonica lites are PCR-based markers that are both technically subspecies,with japonica divided into temperate and tropical types.efficient and cost-effective to use and are available for With stepwise discrimination,two subsets of approximately30mark-rice(Chen et al.,1997;Temnykh et al.,2000).Compared ers were identified that produced genetic distance matrices and den-with RFLPs,microsatellite markers detect a signifi-drograms that were the same as those produced by means of all
cantly higher degree of polymorphism in rice(Wu and 111markers.The results suggested that a relatively small number of
Tanksley,1993;Yang et al.,1994),and are especially microsatellite markers could be used for the estimation of genetic
suitable for evaluating genetic diversity among closely diversity and the identification of rice cultivars.
related rice cultivars(Akagi et al.,1997).
The cultivated Asian rice species,O.sativa,is com-R ice has one of the largest ex situ germplasm collec-1988).Indica is the predominant tropical subspecies.
posed of two subspecies,indica and japonica(Oka, tions in the world(Jackson and Juggan,1993).This
The japonica subspecies,consisting of temperate and accessible collection of diverse cultivated and wild rice
tropical types,is widely grown in East Asia,North and germplasm has made great contributions to rice breed-
South America,Australia,Mediterranean North Africa, ing.The development of isozyme and,later,DNA
and Europe,and accounts for about20%of world rice marker technology has provided an efficient tool to
production(Mackill,1995).The genetic diversity of ja-facilitate plant genetic resource conservation and man-
ponica rice is thought to be lower than for indica rice agement.In rice,molecular markers have been used to
(Glaszmann,1987;Zhang et al.,1992).The use of wide identify accessions(Olufowote et al.,1997;Virk et al.,
crosses between different subspecies often results in 1995),to determine the genetic structure and pattern
sterility problems in the hybrids and their progenies, of diversity for cultivars of interest(Akagi et al.,1997;
disruption of favorable linkage blocks and gene combi-Mackill,1995;Yang et al.,1994;Zhang et al.,1992),and
nations,and linkage drag(Ikehashi and Araki,1986). to optimize the assembly of core collections(Schoen
The reduced recombination and distorted segregation and Brown,1995).Compared to morphological analysis,
resulting from wide hybridization may cause difficulties
in selection for desired recombinants during the breed-J.Ni,Dep.of Agronomy&Range Science,Univ.of California,Davis,ing process(Pham and Bougerol,1993).From the view-CA95616-8515USA;P.M.Colowit,USDA-ARS,Dep.of Agron-
point of rice breeders,it is preferable to identify and omy&Range Science,Univ.of California,Davis,CA95616-8515
USA;and D.J.Mackill,International Rice Research Institute,DAPO
Abbreviations:AFLP,amplified fragment length polymorphism; Box7777,Metro Manila,Philippines.Received3Nov.2000.*Corre-
MAS,marker assisted selection;RAPD,random amplified polymor-sponding author(d.mackill@https://www.doczj.com/doc/915491003.html,).
phic DNA;RFLP,restriction fragment length polymorphism;simple
sequence repeat,SSR.
Published in Crop Sci.42:601–607(2002).
602CROP SCIENCE,VOL.42,MARCH–APRIL2002
Table1.List of rice accessions used to study microsatellite Table2.List of microsatellite markers used in the study.Marker marker variation.designations are from Chen et al.(1997)and Temnykh et al.
(2000).
Name Origin Subspecies–group
Chromosome Microsatellite marker
Black Gora India Indica
IR40931Philippines Indica1RM5,RM9,RM81A,RM84,RM212,RM220,
IR50R IRRI Indica RM237,RM238A,RM243,RM246,RM259,RM IR36IRRI Indica1,RM23,RM265,RM315,RM302
Hunan Late Indica2China Indica2RM207,RM211,RM233A,RM240,RM250,RM262, N-22India Indica RM263,RM6,RM213,RM341,RM266
GIZA178Africa Indica3RM232,RM251,RM130,RM22,RM135,RM156, GZ5121-5-2-1Africa Indica RM55,RM338,RM60
GZ5470-14-1-2Africa Indica4RM261,RM241,RM142,RM127,RM177,RM317, Teqing China Indica RM348,RM307,RM185
L-202USA-Ca Japonica-tropical5RM153,RM31,RM169,RM173,RM178,RM13,
L-203USA-Ca Japonica-tropical RM291,RM274,RM334
Labelle USA-So Japonica-tropical6RM30,RM3,RM204,RM253,RM136,RM170,
87Y550USA-Ca Japonica-tropical RM340,RM345,RM193
Lemont USA-So Japonica-tropical7RM82,RM234,RM214,RM172,RM51,RM10, Moroberekan Africa Japonica-tropical RM180
Katy USA-So Japonica-tropical8RM152,RM137,RM52,RM126,RM223,RM230, Newbonnet USA-So Japonica-tropical RM337,RM264,RM256
M-103USA-Ca Japonica-temperate9RM215,RM105,RM219,RM160,RM245,RM296, M-201USA-Ca Japonica-temperate RM278
M-202USA-Ca Japonica-temperate10RM228,RM258,RM244,RM239,RM171,RM222, M-203USA-Ca Japonica-temperate RM271,RM311
M-204USA-Ca Japonica-temperate11RM21,RM167,RM202,RM209,RM224,RM229, M-401USA-Ca Japonica-temperate RM254,RM332,RM287
Italica Livorno Italy Japonica-temperate12RM247,RM235,RM155,RM20,RM17,RM313, WC1403Korea Japonica-temperate RM309,RM270
Akitakomachi Japan Japonica-temperate
Koshihikari Japan Japonica-temperate
Yukihikari Japan Japonica-temperate lite primer pairs were chosen to represent the entire rice ge-Arborio Italy Japonica-temperate
nome at about15-to20-centimorgan intervals on the basis Calmochi102USA-CA Japonica-temperate
Calrose USA-CA Japonica-temperate of the published rice microsatellite framework map(Temnykh Taipei309China Japonica-temperate et al.,2000)(Table2).The original sources and motifs for Uz Ros269Russia Japonica-temperate these markers can be found in Temnykh et al.(2000)and in Daegwanbyeo Korea Japonica-temperate
the RiceGenes database(https://www.doczj.com/doc/915491003.html,/rice; S-201USA-CA Japonica-temperate
Hirayana Japan Japonica-temperate verified October2,2001).Polymerase chain reaction(PCR) GIZA176Africa Japonica-temperate analysis followed procedures recommended by the manufac-O.rufipogon Wild relative turer(ABI Prism377GeneScan Chemistry Guide,PE Biosys-O.nivara Wild relative
tems,Foster City,CA)with minor modifications.It was per-
formed in15?L of a mixture containing50ng DNA,330n M use donors of important traits from within the same
of each primer,250?M of each dNTP,and0.6U Taq DNA
polymerase in reaction buffer[20m M TRIS pH8.0,50m M subspecies or cultivar group.For the application of
KCl, 1.5m M MgCl2,0.1mM EDTA,1mM DTT,50% marker assisted selection(MAS)within a subspecies,it
(v/v)glycerol].Fluorescent d CTPs(330n M)labeled with is important to obtain information on the genetic diver-
a rhodamine dye(R110,R6G)was incorporated into PCR sity within a rice subspecies over different genome re-
products to enable detection of the fragments in the ABI377 gions.The excellent attributes of SSR markers and the
automated sequencing system(Perkin-Elmer).The PCR was availability of over300markers in rice(Temnykh et al.,run as follows:(i)an initial denaturation step of3min at94?C,
2000)make it possible to obtain this information.(ii)35cycles of1min at94?C,2min at55?C,1.5min at72?C, Our objectives were to use microsatellite markers to and(iii)a final extension step for5min at72?C.For some evaluate the genetic variation within a diverse collection specific cDNA derived microsatellites,two different annealing of rice accessions,to determine differences in the pat-
temperatures,61and67?C,were employed as described by
Temnykh et al.(2000).PCR products were analyzed on a terns of diversity within two rice subspecies,to distin-
sequencing gel(5%LongRanger,1?TBE buffer,6M urea)in guish different accessions,and to reveal the genetic rela-
an automated ABI377sequencing apparatus(Perkin-Elmer). tionships among them.
Fragment lengths were estimated using internal size standards
by GeneScan Analysis Software.
MATERIALS AND METHODS
Accessions used in the present study included10indica Data Analysis
cultivars,eight tropical japonica cultivars,20temperate japon-
The number of repeats for each allele was determined by ica cultivars,and O.rufipogon and O.nivara,two close rela-
comparing the size of the PCR product with that of IR36 tives of O.sativa(Table1).Accessions were obtained from the
whose repeat number was characterized by Temnykh et al. Rice Germplasm Center at the International Rice Research
(2000).Estimated repeat number was used in the following Institute(IRRI),Philippines,the Rice Experiment Station,
analysis.The number of alleles per locus was based on an Biggs,CA,and the local collection at Davis,CA.
evaluation of the38O.sativa cultivars and didn’t include the
two wild species.The term polymorphism information content DNA Extraction and SSR Analysis
(PIC)was originally introduced into human genetics by
Botstein et al.(1980).It refers to the value of a marker for DNA extraction from rice leaves was as described in Re-
don?a and Mackill(1998).One hundred-eleven rice microsatel-detecting polymorphism within a population,depending on
NI ET AL.:EVALUATION OF GENETIC DIVERSITY IN RICE SUBSPECIES
603
Table 3.Mean values for allele number and PIC of different classes of microsatellite markers within rice and by subspecies.Both polymorphic and monomorphic microsatellites were included in the calculations.
Class of
Number Number of alleles
PIC value microsatellite of markers
markers O.sativa Indica Japonica O.sativa Indica Japonica Genomic libraries 877.41a? 4.62a 4.64a 0.650a 0.651a 0.501a cDNA-derived 24 4.50b 3.38b 2.88b 0.514b 0.456b 0.335b Poly (GA)n type 707.59a 4.66a 4.77a 0.657a 0.657a 0.512a Other 2-bp 7 6.57ab 4.43a 4.14ab 0.652ab 0.663ab 0.497a 3-bp 27 5.22b 3.81a 3.37b 0.546b 0.504b 0.375a 4-bp 2 3.50b 3.50a 1.50b 0.384b 0.500b 0.250a Complex 5 5.60ab 3.20a 3.20b 0.554a 0.460b 0.329a All
111
6.78
4.35
4.26
0.621
0.609
0.465
?Means in a column followed by different letters are statistically different at P ?0.05.
the number of detectable alleles and the distribution of their 1982)and RFLPs (Wang and Tanksley,1989;Zhang frequency.In present study,PIC value of a marker was calcu-et al.,1992).As a measure of the informativeness of lated according to a simplified version after Anderson et al.microsatellites,the average PIC value was 0.62with the (1993):
range of 0.10(RM60)to 0.91(RM204).
The microsatellite markers derived from the genomic PIC i ?1?
?n
j ?1
P 2ij
library showed significantly higher genetic diversity than those derived from GenBank sequences (Table 3).Com-where P ij is the frequency of the j th allele for the i th marker,paring microsatellite markers with the different repeat and summed over n alleles.The PROC REG of SAS was motifs,those with GA repeats had the greatest number employed to study the relationship between the maximum of alleles and highest PIC values,while the 3-and 4-bp number of simple repeats and number of alleles or PIC value.motif markers had the lowest number of alleles and PIC Average number of alleles,average PIC value,and average values (Table 3).These results were consistent with genetic distance were computed on the basis of different rice those reported by Cho et al.(2000).
subspecies,chromosomes and microsatellite classes,and the means were compared by the GLM (general linear models)There was a relationship between the number of al-procedure of SAS.The Tukey test was used to compare the leles detected at a locus and the maximum number of means of different classes.
simple repeats within the targeted microsatellite DNA The presence (1)and absence (0)of alleles for each microsa-(r ?0.72,P ?0.001).Thus,the larger the maximum tellite marker were recorded for all accessions and then con-repeat number in the microsatellite DNA,the larger verted to a genetic distance matrix.Genetic distances (Nei the number of alleles detected.A significant correlation and Li,1979)between two entries were computed as
between PIC value and the maximum number of single GD ?1?[2N /(N i ?N j )]
repeats per microsatellite marker was also detected (r ?0.69,P ?0.001).
where N is the number of shared bands and N i and N j are the Most microsatellite primers amplified PCR products total number of bands for entries i and j .A cluster diagram in O.rufipogon (89%)and O.nivara (88%).In the case was constructed based on these distances by the UPGMA (average linkage)method using PROC CLUSTER of SAS of null alleles in these species,PCR amplifications were (SAS Institute Inc.,1989).The centroid,median and single repeated to exclude failed PCR reaction as the cause linkage clustering methods of PROC CLUSTER were also of the null allele.The null alleles can arise from point used to observe consistency of the clustering.Groups deter-mutation (s)in one or both of the primer sites.The low mined from the cluster analysis were used for canonical dis-percentage of null alleles in wild relatives of rice implied criminant analysis using the program PROC CANDISC of that most SSR primers developed for rice could be em-SAS.Squared Mahalanobis distances between class means ployed with O.rufipogon and O.nivara ,the close rela-were computed and the first two canonical variables were tive of O.sativa .For about one fifth of primers capable plotted for all accessions.The program PROC STEPDISC of of being amplified in wild relatives (20of 99in O.rufipo-SAS was used to choose the subsets of microsatellite markers that best represented the information in the total dataset.gon and 22of 98in O.nivara ),it was also noted that Pearson correlation coefficients (PROC REG of SAS)were the band sizes of PCR products of wild relatives were used to evaluate the relationship between genetic distances outside the range of those amplified from O.sativa ,calculated on the basis of sublets and the whole dataset.
suggesting that those alleles identified in wild relatives might be unique and different from those detected in RESULTS AND DISCUSSION O.sativa .
SSR Polymorphism in the Entire Sample
Comparison of Polymorphism between Rice
The 111SSR markers revealed 753alleles in the 38Subspecies and Chromosomes
cultivars.The number of alleles per locus varied widely Although there were fewer indica (10)than japonica among these markers,ranging from 1(RM238A and (28)cultivars included in the present study,the average RM193)to 17(RM204)with an average of 6.8.These number of alleles observed was similar in indica (4.4)to numbers are,on a per locus basis,much larger than that in japonica (4.3).The indica group had significantly those reported from previous studies using other types of markers such as isozymes (Glaszmann,1987;Second,
greater average PIC value (0.609)than the japonica
604CROP SCIENCE,VOL.42,MARCH–APRIL2002
https://www.doczj.com/doc/915491003.html,parison of genetic diversity within the indica and japonica groups based on microsatellite markers on different rice chromosomes.
A)Average number of alleles.B)Average of PIC value.
group(0.465)(Table3).The means of genetic distances tivars,and several studies have been performed to char-between cultivar pairs within the subspecies were also
acterize the extent of genetic diversity and differentia-used to evaluate the genetic diversity of different sub-tion of these two rice groups(Oka,1988;Second,1982; species.The average genetic distance for the indica
Yang et al.,1994;Zhang et al.,1992).Some marker group(0.675)was significantly greater than that for the alleles appeared to be diagnostic for rice subspecies. japonica group(0.484)(F?140.0,P?0.001).The
For eight markers(RM240,RM262,RM130,RM156, conclusion that indica rice has a higher level of genetic RM160,RM245,RM271and RM235),the indica culti-variation than japonica rice is in accordance with previ-
vars had alleles that were not found in the japonica ous reports(Mackill,1995;Yang et al.,1994;Zhang et cultivars.For RM130and RM156on chromosome3, al.,1992).However,it should be noted that several
all the indica cultivars had the same allele,and it was closely related japonica cultivars were included.different from any allele found in the japonica cultivars. There has been extensive interest in characterizing
For RM240,RM262,and RM271,all the japonicas had the genetic differences between indica and japonica cul-the same allele,which was not be found in the indica
NI ET AL.:EVALUATION OF GENETIC DIVERSITY IN RICE SUBSPECIES605
Fig.2.Cluster diagram based on genetic distance calculated from111microsatellite marker alleles of38rice cultivars and two wild accessions. cultivars.In some cases,the allele sizes were sufficiently clude complications caused by different microsatellite
types,one subset including87microsatellite markers different to suggest that these alleles could be assessed
on agarose gels,which would make them attractive for derived from the genomic library and another subset easily identifying subspecies.
including65genomic derived(GA)n microsatellite mark-To our knowledge,there is little information available ers were also used to calculate the means of number of for the difference in genetic diversity of rice subspecies
alleles and PIC value on different chromosomes for the for specific rice chromosomes.In the present study,the two https://www.doczj.com/doc/915491003.html,pared with the results based on number of alleles and PIC value for markers on different
the whole dataset,similar conclusions were drawn from chromosomes for indica and japonica groups were calcu-those two subsets(data not shown).
lated to evaluate the genetic diversity.Both indica and
The information on genetic diversity of rice subspe-japonica groups showed a high level genetic variation cies for specific genomic regions will be quite useful for
rice breeding programs.A major application of this on chromosome11(Fig.1).The number of alleles on
that chromosome was34%higher than the average work is to determine the feasibility of mapping genes based on all12chromosomes,and the average PIC
within the japonica subspecies,and in particular,within values were20%(indica)and30%(japonica)higher.the temperate japonica group,to which most California On the other hand,chromosomes5and8had relatively
cultivars belong.Some traits such as cooking quality lower genetic diversity for both groups(Fig.1).How-cannot be accurately measured in wide crosses,where
the grain quality requirements are completely divergent. ever,diversity of indica and japonica groups differed
on chromosomes2,6,and7.For chromosomes6and The data reported here indicate that it should be possi-7,the indica group showed significantly lower genetic
ble to obtain adequate polymorphism in crosses be-diversity than the japonica group.In contrast,for chro-tween California cultivars and premium quality Japa-mosome2,genetic variation of indica rice was much
nese cultivars such as Koshihikari to map traits of interest. higher than that of the japonica group(Fig.1).To ex-For some traits controlled by the specific loci on chro-
606CROP SCIENCE,VOL.42,MARCH–APRIL2002
Table4.The two microsatellite marker subsets that fully charac-between tropical and temperate japonica types is not terize the rice accessions.firm(Glaszmann and Arraudeau,1986;Mackill,1995). Method Identified markers For indica subspecies,with the same standard(GD?
0.56),10cultivars could be divided into six subclusters Forward RM130,RM334,RM173,RM170,RM84,RM256,
RM241,RM212,RM13,RM237,RM23,RM258,(Fig.2).Considering the high level genetic diversity
RM137,RM291,RM52,RM287,RM229,RM213,in the indica cultivars,GD?0.62was also used for
RM169,RM222,RM60,RM1,RM51,RM127,
subcluster analysis.In this case,the10indica accessions RM302,RM270,RM9,RM81A,RM232,RM207,
RM271could be divided into three subgroups,corresponding to Backward RM5,RM9,RM81A,RM84,RM212RM220,RM237,Indian upland cultivars,Egyptian cultivars,and tropical RM243,RM246,RM259,RM1,RM23,RM265,
RM315,RM302,RM207,RM211,RM233A,Asian lowland cultivars.On the whole,the clustering
RM240,RM250,RM262,RM263,RM6,RM213,results revealed by SSR closely reflected the previously
RM341,RM266,RM232,RM251,RM130,RM22,understood relationship among these rice accessions.
RM135,RM156,RM55,RM338,RM60,RM261,
RM241The indica and the two japonica groups determined
from the cluster analysis were used to perform the ca-
nonical discriminant analysis.The first two canonical mosome6and7,it will be easy for a breeder to transfer variables were plotted to observe the relationship of the the desirable trait using MAS by crossing within japon-three rice cultivar groups(data not shown).By means of ica subspecies.However,for the traits controlled by loci111microsatellite markers,each group could be clearly on chromosome2,it might be difficult to obtain markers distinguished from the others.The squared distances for use in marker-assisted breeding.Furthermore,the between the indica and japonica groups were536(tropi-differences in microsatellite diversity may reflect other cal)and534(temperate)compared to57between tropi-underlying genetic similarities,implying that one might cal and temperate japonica s.
not find sources of new alleles for traits controlled by To identify an efficient subset of microsatellite mark-genes on this chromosome.Resistance to stem rot(Scle-ers,the dataset was subject to STEPDISC analysis.With rotium oryzae Cattaneo)in rice may be an example of forward and backward strategies,two subsets of micro-this.Resistance to this disease was not found among satellite markers,consisting of31and37markers,were japonica cultivars,and was introduced from an accession identified(Table4).Average allele numbers were6.7 of O.rufipogon.One of the important resistance loci and7.0for the forward and backward set compared was mapped on chromosome2(Ni et al.,2001).with6.8for the whole dataset.PIC values were0.58and
0.65for the forward and backward set compared with
Clustering of Rice Cultivars0.62for the whole dataset.The31microsatellites identi-
with Microsatellite Markers fied from FORWARD STEPDISC analysis were evenly
distributed on most of rice chromosomes with the ex-All38cultivated accessions and the two wild relatives
ception of chromosome11,while the37microsatellites could be easily distinguished even though some acces-
from BACKWARD STEPDISC analysis were mainly sions were closely related.The UPGMA cluster diagram
located on chromosomes1,2,3,and4.Both subsets showed two major clusters corresponding to the indica
included the microsatellites derived from the genomic and japonica subspecies,with additional sub-clusters
library and the GenBank sequences.Some markers di-within both indica and japonica clusters(Fig.2).The
agnostic for the rice subspecies,were involved in both same major groups and sub-clusters were observed by
subsets(RM130and RM271in the FORWARD subset, the centroid hierarchical,median hierarchical and single
RM130,RM240,RM262,and RM156in the BACK-linkage clustering methods.
WARD subset).These two subsets of markers were With genetic distance(GD)?0.56as the standard
used to calculate the genetic distances and cluster analy-for a subcluster,the japonica cluster could be divided
sis.All38cultivated accessions and two wild relatives into two groups.One group was the tropical japonica
could still be easily distinguished.A significant correla-cultivars that included three California long-grain culti-
tion between the genetic distances calculated on the vars and four southern U.S.cultivars.The second cluster
basis of the total dataset and those based on the subsets contained temperate japonica cultivars and consisted
was found(for total/forward,r?0.983,P?0.001;for of two subgroups that remained together in different
total/backward,r?0.971,P?0.001).The cluster analy-clustering methods.One subgroup contained typical
ses based on these two subsets corresponded exactly to California medium grain cultivars(M-103,M-201,M-202,
that based on the whole dataset(data not shown).The M-203,M-401,M-204and Calrose).The other subgroup
results suggested that a relatively small number of mi-mainly contained temperate japonica cultivars from
crosatellite markers could be employed to evaluate the East Asia(Akitakomachi,Koshihikari,Yukihikari,and
genetic diversity,to identify different accessions,and to Daegwanbyeo).The remaining temperate japonica ac-
reveal the genetic relationship among them. cessions,however,could not be clustered with these two
subgroups.Morobereban,a tropical japonica cultivar,
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比较级与最高级 1.as...as 与(not) as(so)...as as...as...句型中，as的词性 第一个as是副词，用在形容词和副词的原级前，常译为“同样地”。第二个as是连词，连接与前面句子结构相同的一个句子(相同部分常省略)，可译为“同..... He is as tall as his brother is (tall) . (后面的as 为连词) 只有在否定句中，第一个as才可换为so 改错: He is so tall as his brother.（X） 2.在比较状语从句中，主句和从句的句式结构一般是相同的 与as...as 句式中第二个as一样，than 也是连词。as和than这两个连词后面的从句的结构与前面的句子大部分情况下结构是相同的，相同部分可以省略。 He picked more apples than she did. 完整的表达为: He picked more apples than she picked apples. 后而的picked apples和前面相同，用did 替代。 He walked as slowly as she did.完整表达为: He walked as slowly as she walked slowly. she后面walked slowly与前面相同，用did替代。
3.谓语的替代 在as和than 引导的比较状语从句中，由于句式同前面 主句相同，为避免重复，常把主句中出现而从句中又出现的动词用do的适当形式来代替。 John speaks German as fluently as Mary does. 4.前后的比较对象应一致 不管后面连词是than 还是as,前后的比较对象应一致。The weather of Beijing is colder than Guangzhou. x than前面比较对象是“天气”，than 后面比较对象是“广州”，不能相比较。应改为: The weather of Bejing is colder than that of Guangzhou. 再如: His handwriting is as good as me. 应改为: His handwriting is as good as mine. 5.可以修饰比较级的词 常用来修饰比较级的词或短语有: Much,even,far,a little,a lot,a bit,by far,rather,any,still,a great deal等。 by far的用法: 用于强调，意为“...得多”“最最...”“显然”等，可修饰形容词或副词的比较级和最高级，通常置于其后，但是若比较级或最高级前有冠词，则可置于其前或其后。
The way 的用法 Ⅰ常见用法： 1)the way+ that 2)the way + in which（最为正式的用法） 3)the way + 省略（最为自然的用法） 举例：I like the way in which he talks. I like the way that he talks. I like the way he talks. Ⅱ习惯用法： 在当代美国英语中，the way用作为副词的对格，“the way+ 从句”实际上相当于一个状语从句来修饰整个句子。 1)The way =as I am talking to you just the way I’d talk to my own child. He did not do it the way his friends did. Most fruits are naturally sweet and we can eat them just the way they are—all we have to do is to clean and peel them. 2）The way= according to the way/ judging from the way The way you answer the question, you are an excellent student. The way most people look at you, you’d think trash man is a monster. 3）The way =how/ how much No one can imagine the way he missed her. 4）The way =because
人教版（新目标）初中英语形容词与副词的比较级与最高级 （一）规则变化： 1．绝大多数的单音节和少数双音节词，加词尾-er ，-est tall—taller—tallest 2．以不发音的e结尾的单音节词和少数以-le结尾的双音节词只加-r，-st nice—nicer—nicest , able—abler—ablest 3．以一个辅音字母结尾的重读闭音节词或少数双音节词，双写结尾的辅音字母，再加-er，-est big—bigger—biggest 4．以辅音字母加y结尾的双音节词，改y为i再加-er，-est easy—easier—easiest 5．少数以-er，-ow结尾的双音节词末尾加-er，-est clever—cleverer—cleverest, narrow—narrower—narrowest 6．其他双音节词和多音节词，在前面加more，most来构成比较级和最高级 easily—more easily—most easily （二）不规则变化 常见的有： good / well—better—best ; bad (ly)/ ill—worse—worst ; old—older/elder—oldest/eldest many / much—more—most ; little—less—least ; far—farther/further—farthest/furthest
用法： 1．原级比较：as + adj./adv. +as（否定为not so/as + adj./adv. +as）当as… as中间有名字时，采用as + adj. + a + n.或as + many / much + n. This is as good an example as the other is . I can carry as much paper as you can. 表示倍数的词或其他程度副词做修饰语时放在as的前面 This room is twice as big as that one. 倍数+as+adj.+as = 倍数+the +n.+of Your room is twice as larger as mine. = Your room is twice the size of mine. 2．比较级+ than 比较级前可加程度状语much, still, even, far, a lot, a little, three years. five times,20%等 He is three years older than I (am). 表示“（两个中）较……的那个”时，比较级前常加the（后面有名字时前面才能加冠词） He is the taller of the two brothers. / He is taller than his two brothers. Which is larger, Canada or Australia? / Which is the larger country, Canada or Australia? 可用比较级形式表示最高级概念，关键是要用或或否定词等把一事物（或人）与其他同类事物（或人）相分离 He is taller than any other boy / anybody else.
大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基础上变化的。分为规则变化和不规则变化。 规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加 -er 和 -est 构成。 great (原级) (比较级) (最高级) 2) 以 -e 结尾的单音节形容词的比较级和最高级是在词尾加 -r 和 -st 构成。wide (原级) (比较级) (最高级) 3)少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和 -est 构成。 clever(原级) (比较级) (最高级) 4) 以 -y 结尾,但 -y 前是辅音字母的形容词的比较级和最高级是把 -y 去掉,加上 -ier 和-est 构成. happy (原形) (比较级) (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该辅音字母然后再加 -er和-est。 big (原级) (比较级) (最高级) 6) 双音节和多音节形容词的比较级和最高级需用more 和 most 加在形容词前面来构成。 beautiful (原级) (比较级) (比较级) difficult (原级) (最高级) (最高级) 常用的不规则变化的形容词的比较级和最高级: 原级------比较级------最高级 good------better------best many------more------most much------more------most bad------worse------worst far------farther, further------farthest, furthest 形容词前如加 less 和 least 则表示"较不"和"最不 形容词比较级的用法: 形容词的比较级用于两个人或事物的比较,其结构形式如下: 主语+谓语(系动词)+ 形容词比较级+than+ 对比成分。也就是, 含有形容词比较级的主句+than+从句。注意从句常常省去意义上和主句相同的部分, 而只剩下对比的成分。
The way的用法及其含义（二） 二、the way在句中的语法作用 the way在句中可以作主语、宾语或表语： 1.作主语 The way you are doing it is completely crazy.你这个干法简直发疯。 The way she puts on that accent really irritates me. 她故意操那种口音的样子实在令我恼火。The way she behaved towards him was utterly ruthless. 她对待他真是无情至极。 Words are important, but the way a person stands, folds his or her arms or moves his or her hands can also give us information about his or her feelings. 言语固然重要,但人的站姿,抱臂的方式和手势也回告诉我们他(她)的情感。 2.作宾语 I hate the way she stared at me.我讨厌她盯我看的样子。 We like the way that her hair hangs down.我们喜欢她的头发笔直地垂下来。 You could tell she was foreign by the way she was dressed. 从她的穿著就可以看出她是外国人。 She could not hide her amusement at the way he was dancing. 她见他跳舞的姿势，忍俊不禁。 3.作表语 This is the way the accident happened.这就是事故如何发生的。 Believe it or not, that's the way it is. 信不信由你, 反正事情就是这样。 That's the way I look at it, too. 我也是这么想。 That was the way minority nationalities were treated in old China. 那就是少数民族在旧中
英语比较级和最高级的用法归纳 在学习英语过程中，会遇到很多的语法问题，比如比较级和最高级的用法，对于 这些语法你能够掌握吗？下面是小编整理的英语比较级和最高级的用法，欢迎阅读！ 英语比较级和最高级的用法 一、形容词、副词的比较级和最高级的构成规则 1.一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级 在后面加-est; (1)单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest (2)双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2.以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st; 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3.在重读闭音节(即：辅音+元音+辅音)中，先双写末尾的辅音字母，比较级加-er，最高级加-est; 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4.以“辅音字母+y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est; 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5.其他双音节词和多音节词，比较级在前面加more，最高级在前面加most; 如：bea utiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily 注意：(1)形容词最高级前通常必须用定冠词 the，副词最高级前可不用。 例句： The Sahara is the biggest desert in the world. (2) 形容词most前面没有the，不表示最高级的含义，只表示"非常"。 It is a most important problem. =It is a very important problem.
定冠词the的用法： 定冠词the与指示代词this ,that同源,有“那(这)个”的意思,但较弱,可以和一个名词连用,来表示某个或某些特定的人或东西. (1)特指双方都明白的人或物 Take the medicine.把药吃了. (2)上文提到过的人或事 He bought a house.他买了幢房子. I've been to the house.我去过那幢房子. (3)指世界上独一无二的事物 the sun ,the sky ,the moon, the earth (4)单数名词连用表示一类事物 the dollar 美元 the fox 狐狸 或与形容词或分词连用,表示一类人 the rich 富人 the living 生者 (5)用在序数词和形容词最高级,及形容词等前面 Where do you live?你住在哪? I live on the second floor.我住在二楼. That's the very thing I've been looking for.那正是我要找的东西. (6)与复数名词连用,指整个群体 They are the teachers of this school.(指全体教师) They are teachers of this school.(指部分教师) (7)表示所有,相当于物主代词,用在表示身体部位的名词前 She caught me by the arm.她抓住了我的手臂. (8)用在某些有普通名词构成的国家名称,机关团体,阶级等专有名词前 the People's Republic of China 中华人民共和国 the United States 美国 (9)用在表示乐器的名词前 She plays the piano.她会弹钢琴. (10)用在姓氏的复数名词之前,表示一家人 the Greens 格林一家人(或格林夫妇) (11)用在惯用语中 in the day, in the morning... the day before yesterday, the next morning... in the sky... in the dark... in the end... on the whole, by the way...
More than的用法 A. “More than+名词”表示“不仅仅是” 1)Modern science is more than a large amount of information. 2)Jason is more than a lecturer; he is a writer, too. 3) We need more than material wealth to build our country.建设我们国家，不仅仅需要物质财富. B. “More than+数词”含“以上”或“不止”之意，如： 4)I have known David for more than 20 years. 5)Let's carry out the test with more than the sample copy. 6) More than one person has made this suggestion. 不止一人提过这个建议. C. “More than+形容词”等于“很”或“非常”的意思，如： 7)In doing scientific experiments, one must be more than careful with the instruments. 8)I assure you I am more than glad to help you. D. more than + (that)从句，其基本意义是“超过（=over）”，但可译成“简直不”“远非”.难以，完全不能（其后通常连用情态动词can） 9) That is more than I can understand . 那非我所能懂的. 10) That is more than I can tell. 那事我实在不明白。 11) The heat there was more than he could stand. 那儿的炎热程度是他所不能忍受的 此外，“more than”也在一些惯用语中出现，如： more...than 的用法 1. 比……多，比……更 He has more books than me. 他的书比我多。 He is more careful than the others. 他比其他人更仔细。 2. 与其……不如 He is more lucky than clever. 与其说他聪明，不如说他幸运。 He is more （a）scholar than （a）teacher. 与其说他是位教师，不如说他是位学者。 注：该句型主要用于同一个人或物在两个不同性质或特征等方面的比较，其中的比较级必须用加more 的形式，不能用加词尾-er 的形式。 No more than/not more than 1. no more than 的意思是“仅仅”“只有”“最多不超过”，强调少。如： --This test takes no more than thirty minutes. 这个测验只要30分钟。 --The pub was no more than half full. 该酒吧的上座率最多不超过五成。-For thirty years，he had done no more than he （had）needed to. 30年来，他只干了他需要干的工作。 2. not more than 为more than （多于）的否定式，其意为“不多于”“不超过”。如：Not more than 10 guests came to her birthday party. 来参加她的生日宴会的客人不超过十人。 比较： She has no more than three hats. 她只有3顶帽子。（太少了） She has not more than three hats. 她至多有3顶帽子。（也许不到3顶帽子） I have no more than five yuan in my pocket. 我口袋里的钱最多不过5元。（言其少） I have not more than five yuan in my pocket. 我口袋里的钱不多于5元。（也许不到5元） more than, less than 的用法 1. （指数量）不到，不足 It’s less than half an hour’s drive from here. 开车到那里不到半个钟头。 In less than an hour he finished the work. 没要上一个小时，他就完成了工作。 2. 比……（小）少 She eats less than she should. 她吃得比她应该吃的少。 Half the group felt they spent less than average. 半数人觉得他们的花费低于平均水平。 more…than,/no more than/not more than (1)Mr．Li is ________ a professor; he is also a famous scientist． (2)As I had ________ five dollars with me, I couldn’t afford the new jacket then． (3)He had to work at the age of ________ twelve． (4)There were ________ ten chairs in the room．However, the number of the children is twelve． (5)If you tel l your father what you’ve done, he’ll be ________ angry． (6)－What did you think of this novel? －I was disappointed to find it ________ interesting ________ that one． 倍数表达法 1. “倍数+形容词（或副词）的比较级+than+从句”表示“A比B大（长、高、宽等）多少倍” This rope is twice longer than that one.这根绳是那根绳的三倍（比那根绳长两倍）。The car runs twice faster than that truck.这辆小车的速度比那辆卡车快两倍（是那辆卡车的三倍）。 2. “倍数+as+形容词或副词的原级+as+从句”表示“A正好是B的多少倍”。
“tｈｅwａｙ+从句”结构的意义及用法 首先让我们来看下面这个句子: Ｒead the foｌloｗｉnｇpassagｅａnd talkａbout ｉt wi ｔh your classmaｔes．Try tｏｔeｌl whaｔyｏu thiｎk ｏf Tom aｎd ｏｆｔhe ｗay the chiｌｄrenｔrｅated ｈim. 在这个句子中，ｔhe waｙ是先行词,后面是省略了关系副词that或in whｉch的定语从句。 下面我们将叙述“the ｗaｙ+从句”结构的用法。 1.tｈe wａy之后，引导定语从句的关系词是tｈat而不是hoｗ,因此，<<现代英语惯用法词典＞＞中所给出的下面两个句子是错误的：Ｔhｉs is ｔｈeｗayｈowｉtｈａppened. This is the way how he ａlwａｙs treats me. 2．在正式语体中,thaｔ可被in which所代替;在非正式语体中，ｔhat则往往省略。由此我们得到theｗay后接定语从句时的三种模式：1) tｈe ｗaｙ＋ｔhａt-从句２）the way +ｉn whiｃh－从句3) the ｗay +从句 例如：Ｔｈe way(in whiｃh ，thａt) ｔhｅｓｅｃomｒade ｓloｏｋａｔｐrobｌems is wrong．这些同志看问题的方法
不对。 Ｔｈｅｗａy(that ,ｉn ｗhiｃh)yoｕ’ｒe doinｇit is comple ｔeｌy crａzy.你这么个干法,简直发疯。 Wｅａdmiｒｅd him for thｅｗay ｉｎｗhｉch he fａｃeｓdiｆficultieｓ． Waｌlａｃe ａｎd Ｄarwiｎｇreed ｏn the way ｉｎwhi ｃh ｄｉfｆｅrｅnt forms ｏf life had ｂegｕn.华莱士和达尔文对不同类型的生物是如何起源的持相同的观点。 Thｉs is ｔｈe ｗaｙ（tｈａｔ) hｅdｉd it. I lｉkeｄｔhe waｙ(ｔhat) ｓｈeｏｒganized ｔhe ｍeetｉng． 3.theｗay(tｈat)有时可以与hｏw(作“如何”解）通用。例如： That’s tｈe ｗaｙ(tｈaｔ) shｅspoke. = Tｈat’s how shｅspoke.
初中英语比较级和最高级讲解与练习 形容词比较级和最高级 一．绝大多数形容词有三种形式,原级,比较级和最高级, 以表示形容词说明的性质在程度上的不同。 1. 形容词的原级: 形容词的原级形式就是词典中出现的形容词的原形。例如: poor tall great glad bad 2. 形容词的比较级和最高级: 形容词的比较级和最高级形式是在形容词的原级形式的基 础上变化的。分为规则变化和不规则变化。 二．形容词比较级和最高级规则变化如下: 1) 单音节形容词的比较级和最高级形式是在词尾加-er 和-est 构成。 great (原级) greater(比较级) greatest(最高级) 2) 以-e 结尾的单音节形容词的比较级和最高级是在词尾加-r 和-st 构成。 wide (原级) wider (比较级) widest (最高级) 3) 少数以-y, -er, -ow, -ble结尾的双音节形容词的比较级和最高级是在词尾加 -er 和-est构成。 clever(原级) cleverer(比较级) cleverest(最高级)， slow(原级) slower(比较级) slowest (最高级) 4) 以-y 结尾,但-y 前是辅音字母的形容词的比较级和最高级是把-y 去掉,加上-ier 和-est 构成. happy (原形) happier (比较级) happiest (最高级) 5) 以一个辅音字母结尾其前面的元音字母发短元音的形容词的比较级和最高级是双写该 辅音字母然后再加-er和-est。 原形比较级最高级原形比较级最高级 big bigger biggest hot hotter hottest red redder reddest thin thinner thinnest 6) 双音节和多音节形容词的比较级和最高级需用more 和most 加在形容词前面来构 成。 原形比较级最高级 careful careful more careful most careful difficult more difficult most difficult delicious more delicious most delicious 7)常用的不规则变化的形容词的比较级和最高级: 原级比较级最高级 good better best 好的 well better best 身体好的 bad worse worst 坏的 ill worse worst 病的 many more most 许多 much more most 许多 few less least 少数几个 little less least 少数一点儿 （little littler littlest 小的） far further furthest 远（指更进一步，深度。亦可指更远） far farther farthest 远（指更远，路程）
表示“方式”、“方法”，注意以下用法： 1.表示用某种方法或按某种方式，通常用介词in(此介词有时可省略)。如： Do it (in) your own way. 按你自己的方法做吧。 Please do not talk (in) that way. 请不要那样说。 2.表示做某事的方式或方法，其后可接不定式或of doing sth。 如： It’s the best way of studying [to study] English. 这是学习英语的最好方法。 There are different ways to do [of doing] it. 做这事有不同的办法。 3.其后通常可直接跟一个定语从句(不用任何引导词)，也可跟由that 或in which 引导的定语从句，但是其后的从句不能由how 来引导。如： 我不喜欢他说话的态度。 正：I don’t like the way he spoke. 正：I don’t like the way that he spoke. 正：I don’t like the way in which he spoke. 误：I don’t like the way how he spoke. 4.注意以下各句the way 的用法： That’s the way (=how) he spoke. 那就是他说话的方式。 Nobody else loves you the way(=as) I do. 没有人像我这样爱你。 The way (=According as) you are studying now, you won’tmake much progress. 根据你现在学习情况来看，你不会有多大的进步。 2007年陕西省高考英语中有这样一道单项填空题： ——I think he is taking an active part insocial work. ——I agree with you_____. A、in a way B、on the way C、by the way D、in the way 此题答案选A。要想弄清为什么选A，而不选其他几项，则要弄清选项中含way的四个短语的不同意义和用法，下面我们就对此作一归纳和小结。 一、in a way的用法 表示：在一定程度上，从某方面说。如： In a way he was right.在某种程度上他是对的。注：in a way也可说成in one way。 二、on the way的用法 1、表示：即将来(去)，就要来(去)。如： Spring is on the way.春天快到了。 I'd better be on my way soon.我最好还是快点儿走。 Radio forecasts said a sixth-grade wind was on the way.无线电预报说将有六级大风。 2、表示：在路上，在行进中。如： He stopped for breakfast on the way.他中途停下吃早点。 We had some good laughs on the way.我们在路上好好笑了一阵子。 3、表示：(婴儿)尚未出生。如： She has two children with another one on the way.她有两个孩子，现在还怀着一个。 She's got five children，and another one is on the way.她已经有5个孩子了，另一个又快生了。 三、by the way的用法
形容词比较级和最高级的形式 一、形容词比较级和最高级的构成 形容词的比较级和最高级变化形式规则如下 构成法原级比较级最高级 ①一般单音节词末尾加 er 和 est strong stronger strongest ②单音节词如果以 e结尾，只加 r 和 st strange stranger strangest ③闭音节单音节词如末尾只有一个辅音字母， 须先双写这个辅音字母，再加 er和 est sad big hot sadder bigger hotter saddest biggest hottest ④少数以 y, er(或 ure), ow, ble结尾的双音节词， 末尾加 er和 est(以 y结尾的词，如 y前是辅音字母， 把y变成i，再加 er和 est，以 e结尾的词仍 只加 r和 st) angry Clever Narrow Noble angrier Cleverer narrower nobler angriest cleverest narrowest noblest ⑤其他双音节和多音节词都在前面加单词more和most different more different most different 1) The most high 〔A〕mountain in 〔B〕the world is Mount Everest，which is situated 〔C〕in Nepal and is twenty nine thousand one hundred and fourty one feet high 〔D〕 . 2) This house is spaciouser 〔A〕than that 〔B〕white 〔C〕one I bought in Rapid City，South Dakota 〔D〕last year. 3) Research in the social 〔A〕sciences often proves difficulter 〔B〕than similar 〔C〕work in the physical 〔D〕sciences. 二、形容词比较级或最高级的特殊形式：
比较级和最高级 1.在形容词词尾加上―er‖ ―est‖ 构成比较级、最高级： bright（明亮的）—brighter—brightest broad（广阔的）—broader—broadest cheap（便宜的）—cheaper—cheapest clean（干净的）—cleaner—cleanest clever（聪明的）—cleverer—cleverest cold（寒冷的）—colder—coldest cool（凉的）—cooler—coolest dark（黑暗的）—darker—darkest dear（贵的）—dearer—dearest deep（深的）—deeper—deepest fast（迅速的）—faster—fastest few（少的）—fewer—fewest great（伟大的）—greater—greatest hard（困难的,硬的）—harder—hardest high（高的）—higher—highest kind（善良的）—kinder—kindest light（轻的）—lighter—lightest long（长的）—longer—longest loud（响亮的）—louder—loudest low（低的）—lower—lowest near（近的）—nearer—nearest new（新的）—newer—newest poor（穷的）—poorer—poorest quick（快的）—quicker—quickest quiet（安静的）—quieter—quietest rich（富裕的）—richer—richest short（短的）—shorter—shortest slow（慢的）—slower—slowest small（小的）—smaller—smallest smart（聪明的）—smarter—smartest soft（柔软的）—softer—softest strong（强壮的）—stronger—strongest sweet（甜的）—sweeter—sweetest tall（高的）-taller-tallest thick（厚的）—thicker—thickest warm（温暖的）—warmer—warmest weak（弱的）—weaker—weakest young（年轻的）—younger—youngest 2.双写最后一个字母,再加上―er‖ ―est‖构成比较级、最高级： big（大的）—bigger—biggest fat（胖的）—fatter—fattest hot（热的）—hotter—hottest red（红的）—redder—reddest sad（伤心的）—sadder—saddest thin（瘦的）—thinner—thinnest wet（湿的）—wetter—wettest mad（疯的）—madder—maddest 3.以不发音的字母e结尾的形容词,加上―r‖ ―st‖ 构成比较级、最高级：able（能干的）—abler—ablest brave（勇敢的）—braver—bravest close（接近的）—closer—closest fine（好的,完美的）—finer—finest large（巨大的）—larger—largest late（迟的）—later—latest nice（好的）—nicer—nicest ripe（成熟的）—riper—ripest
The way的用法及其含义（一） 有这样一个句子：In 1770 the room was completed the way she wanted. 1770年，这间琥珀屋按照她的要求完成了。 the way在句中的语法作用是什么？其意义如何？在阅读时，学生经常会碰到一些含有the way 的句子，如：No one knows the way he invented the machine. He did not do the experiment the way his teacher told him.等等。他们对the way 的用法和含义比较模糊。在这几个句子中，the way之后的部分都是定语从句。第一句的意思是，“没人知道他是怎样发明这台机器的。”the way的意思相当于how；第二句的意思是，“他没有按照老师说的那样做实验。”the way 的意思相当于as。在In 1770 the room was completed the way she wanted.这句话中，the way也是as的含义。随着现代英语的发展，the way的用法已越来越普遍了。下面，我们从the way的语法作用和意义等方面做一考查和分析： 一、the way作先行词，后接定语从句 以下3种表达都是正确的。例如：“我喜欢她笑的样子。” 1. the way+ in which +从句 I like the way in which she smiles. 2. the way+ that +从句 I like the way that she smiles. 3. the way + 从句(省略了in which或that) I like the way she smiles. 又如：“火灾如何发生的，有好几种说法。” 1. There were several theories about the way in which the fire started. 2. There were several theories about the way that the fire started.
英语语法---比较级和最高级的用法 在英语中通常用下列方式表示的词:在形容词或副词前加more(如 more natural,more clearly )或加后缀 -er(newer,sooner )。典型的是指形容词或副词所表示的质、量或关系的增加。英语句子中，将比较两个主体的方法叫做“比较句型”。其中，像“A比B更……”的表达方式称为比较级；而“A最……”的表达方式则称为最高级。组成句子的方式是将形容词或副词变化成比较级或最高级的形态。 一、形容词、副词的比较级和最高级的构成规则 1．一般单音节词和少数以-er，-ow结尾的双音节词，比较级在后面加-er，最高级在后面加-est； （1）单音节词 如：small→smaller→smallest short→shorter→shortest tall→taller→tallest great→greater→greatest （2）双音节词 如：clever→cleverer→cleverest narrow→narrower→narrowest 2．以不发音e结尾的单音节词，比较在原级后加-r，最高级在原级后加-st； 如：large→larger→largest nice→nicer→nicest able→abler→ablest 3．在重读闭音节（即：辅音＋元音＋辅音）中，先双写末尾的辅音字母，比较级加-er，最高级加-est； 如：big→bigger→biggest hot→hotter→hottest fat→fatter→fattest 4．以“辅音字母＋y”结尾的双音节词，把y改为i，比较级加-er，最高级加-est； 如：easy→easier→easiest heavy→heavier→heaviest busy→busier→busiest happy→happier→happiest 5．其他双音节词和多音节词，比较级在前面加more，最高级在前面加most； 如：beautiful→more beautiful→most beautiful different→more different→most different easily→more easily→most easily