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以色列“进化峡谷”野生二棱大麦种子休眠与幼苗抗旱研究(英文)



全 文 :书第29卷 第1期
 2011年3月 
   
四川农业大学学报
Journal of Sichuan Agricultural University
   
Vol.29 No.1
Mar.2011
  收稿日期:2010-11 -22
基金项目:以色列Bona Terra基金项目; 贵州省第六批优秀青年科技人才培养计划(2006-2010)。
责任作者:程剑平(E-mail:agr.jpcheng@gzu.edu.cn)
doi:10.3969/j.issn.1000-2650.2011.01.001
以色列“进化峡谷”野生二棱大麦
种子休眠与幼苗抗旱研究
严 俊1,2,3,王 莹2,Y.Gutterman2,E.Nevo3,程剑平1
(1.贵州大学麦作研究中心,贵阳 550025;
2.本·古里安大学艾伯特·卡兹国际沙漠学院,以色列 思德博克 84990;
3.海法大学进化研究所,以色列 海法 31905)
摘要:野生二棱大麦是栽培大麦的祖先。广泛分布于“新月沃地”及中东地中海气候地区的野生二棱大麦有深度休
眠和幼苗抗旱的重要特性。以色列“进化峡谷”是模拟研究非洲和欧洲不同生境生物进化与多样性的天然实验室。
通过对“进化峡谷”3个微环境的野生二棱大麦种子休眠和幼苗抗旱的研究表明,起源于峡谷南坡(干热的非洲坡)
大麦种子休眠深度大于北坡(冷湿的欧洲坡),峡谷底部居中;而对于幼苗抗旱力则恰好相反,北坡大于南坡,底部仍
居中。大麦种子休眠深度与幼苗抗旱力呈正相关。结果分析显示,微环境在野生二棱大麦种子休眠和幼苗抗旱特
性的自然选择与进化中起明显的决定作用,这两个特性在“进化峡谷”并未受物种内部迁移的影响,而与以色列相应
区域有一致的表现。
关键词:休眠;抗旱;以色列;野生二棱大麦;微环境
中图分类号:S512.3;S330.3+3  文献标志码:A  文章编号:1000-2650(2011)01-0001-05
Caryopsis Dormancy and Seedling Drought Tolerance of Wild Barley,
Hordeum spontaneumatEvolution Canyon Microsite,Israel
JUN Yan1,2,3,YING Wang2,Yitzchak Gutterman2,Eviatar Nevo3,CHENG Jian-ping1
(1.Institute of Triticeae Crops,Guizhou University,Guiyang 550025,China;
2.Albert Katz International School for Desert Studies,Ben-Gurion University of the Negev,
Sede Boker Campus 84990,Israel;
3.Institute of Evolution,University of Haifa,Mount Carmel,Haifa 31905,Israel)
Abstract:Wild barley,Hordeum spontaneum,is the progenitor of cultivated barley(H.vul-
gare).The depth of caryopsis dormancy(germinability)and seedling drought-tolerance are ex-
tremely important characteristics of H.spontaneumin the Mediterranean climate.The dormancy
depth and seedling drought tolerance of wild barley were investigated at three microsites ofEvo-
lution Canyon,Israel.The south-facing slope(SFS)presents the xeric and warmer habitat,the
north-facing slope(NFS)presents the mesic and cooler conditions,and the ecological factors at
the bottom area of the canyon are between SFS and NFS.The obtained results showed that
caryopses from SFS had significantly deeper dormancy than those from the NFS.Moreover,the
seedling revival ability after periods of drought resistance was also significantly higher in
caryopses colected from the SFS than from NFS sites,whereas the dormancy and seedling revival
ability at the bottom of the canyon showed an intermediate inter-slope pattern.Thus,dormancy
depth is positively and significantly correlated with seedling revival after drought.These results
    四川农业大学学报 第29卷
display that the microhabitat environment is the dominant adaptive factor in the natural selection
for seeds dormancy as wel as seedlings drought tolerance of wild barley,and it overrides any in-
ters-lope migration and paralels regional patterns across Israel.
Key words:dormancy;drought tolerance;Israel;wild barley(Hordeum spontaneum);microhabitat
  Wild barley,Hordeum spontaneum,the pro-
genitor of cultivated barley(H.vulgare),is wide-
spread across the near east fertile crescent and
eastern Mediterranean regions[1].Occupied a di-
verse habitats ranging from mesic Mediterranean to
xeric desert in Israel,wild barley exhibits variation
in various traits due to its richness in adaptive di-
versity[2].Caryopsis dormancy and drought-toler-
ance are extremely important survival strategies of
H.spontaneumin the Mediterranean climate[3-4].
The caryopses of H.spontaneumhave developed a
deep dormancy (after-ripening)strategy[5]which
can regulate the proper time and percentage of ger-
mination based on caryopses'evolutionary back-
ground information and current situation[3-4].
Seedlings are able to survive/revive from long peri-
ods of unpredictable desiccation[6].They are able
to develop new adventitious roots and develop into
normal seedlings,even after dehydration to the o-
riginal weight of the caryopsis before wetting for
periods of one to three weeks[7].Both of these
strategies act as survival/revival mechanisms that
ensure plants complete their life cycles under un-
predictable environmental conditions.Better un-
derstanding of relevant mechanisms of dormancy,
and the relationship between the seed dormancy
and its environmental conditions,wil help geneti-
cist and breeders control the dormancy level in
proper time and proper percentages as required[8].
The Evolution Canyon is a Mediterranean
microsite at lower nahal Oren,mount Carmel,Is-
rael[9].It is a summer dry valey.The inter-slope
distance is 100mat bottom and 400mat the top.
Both slopes share the same regional evolutionary
history,geology and climate[10],but differ in the
microclimate of the sites[11].The two contrasting
environmental slopes of Evolution Canyon pro-
vide an ideal site for evolutionary studies on genet-
ic adaptation and incipient speciation.Therefore,
this canyon is an extraordinary natural microscale
evolutionary laboratorie[12].H.spontaneumis an i-
deal plant for the study of the influences of the mi-
cro-environmental factors on the genotypic differ-
ences of plants.The objective of the present study
was to study the relationship between the dorman-
cy depth and seedling drought tolerance of H.
spontaneumat the local natural laboratories,the
Mediterranean microsite designated Evolution
Canyon in Israel.
1 Materials and methods
1.1 Evolution Canyon
The Evolution Canyon is a Mediterranean
microsite at lower nahal Oren,mount Carmel,Is-
rael[9].The tropicalAfrican slopes,or south-fa-
cing slope(SFS)presents xeric and warmer habi-
tat,whereas theEuropean slopes,or north-fa-
cing slope(NFS)represents mesic and cooler habi-
tat.The ecological factors at the bottom area of
the canyon are between the SFS and NFS(Fig.1).
Figure 1 Evolution Canyon
1.2 Plant materials
Caryopses of wild barley were colected at
three sites(NFS,Bottom and SFS)in May,and
then stored them at the gene bank in Institute of e-
volution,university of Haifa.Caryopses were
sown in a field of loess soil with the addition of
compost and drip-irrigation in November.The
fuly mature spikes were harvested in May next

第1期 严 俊(等):以色列“进化峡谷”野生二棱大麦种子休眠与幼苗抗旱研究    
year.Freshly harvested caryopses were stored sep-
arately by ecotype in brown paper bags at 5℃un-
til analysis.The caryopses were used in al of the
experiments.
1.3 Heat-treatment of caryopses and dormancy
break
Freshly harvested caryopses were stored at 5
℃for five months and then transferred to 40℃for
0,14,28,42and 56days.From October to Feb-
ruary next year,six replicates of 40caryopses from
each of the heat-treated caryopsis groups were wet-
ted with 4mL distiled water in a 90-mm-diameter
Petri dish on one piece of Whatman No.1filter pa-
per,and kept at 15℃in the dark for 7days.Dor-
mancy break (measured as germination percent-
age)was checked three times,on days 2,4,and 7
of the incubation[13].A viability test using TTC
(2,3,5-Triphenyl-2H-tetrazolium chloride)was
done with non-germinated caryopses.
1.4 Seedling drought tolerance
Each group of the germinating caryopses were
removed according to the day of germination and
dried in separated and open Petri dishes,on filter
paper,in laboratory conditions(R.H.0%~10%,
at 25~30℃)for four weeks.In such conditions,
around 30days are required until the seedlings
completely dry out[6].The young seedlings(2or 3
days after germination,when the adventitious
roots were ca.3~5cm long)that were exposed to
this drought stress,were rewetted to check their
revival ability after 4weeks of drying.The seed-
lings were rewetted and moved to a dark chamber
at 15℃for 5days.On the fifth day,the revival
percentage was noted after checking regrowth and
the appearance of adventitious roots.Only the
seedlings that were able to develop into normal
plants were calculated[13].
1.5 Statistical analysis
JMP 6.0(SAS Institute)software was used
to perform ANOVA and correlation analyses.
Tukey-Kramer's honest significant difference
(HSD)test was used to compare means of al pairs
(significance level,5%).
2 Results and discussion
2.1 Dormancy depth of caryopses
Remarkably differences in the dormancy depth
of wild barley caryopses were observed among the
three sites.For three treatments of 14,28and 42
days under 40℃,the caryopsis germination after
four days wetting from NFS was significantly high-
er(P<0.05)than those from SFS and the bottom
(Fig.2).The lower the germination rate,the
stronger was the dormancy.Therefore,caryopses
from SFS had deeper dormancy than those from
NFS and the bottom.This local result atEvolu-
tion Canyonparalel the regional results across Is-
rael[5,16].The lower dormancy is an attribute to
the mesic genotypes,whereas the higher dormancy
to the xeric genotypes.In areas with long,hot and
dry summers folowing the season with rain and
mild temperatures,many plants have developed
seeds with primary dormancy[4,17].Like the barley
inhabiting the SFS,the caryopses of barley colect-
ed from the Negev desert and Dead sea reached
lower germination percentages[18].
  Bars represent standard deviation error.Letters a-
bove bars indicate significant differences (P<0.05;
Tukey-Kramer HSD test).Table data represent the ger-
mination percentages(the same as below).
Figure 2 Comparison of germination%
(dormancy depth)of wild barley caryopses among
the three sites of theEvolution Canyon transects
2.2 Revival ability of seedlings
According to one-way ANOVA,there were
significant differences in the revival rates of the

    四川农业大学学报 第29卷
subsequent young seedlings from a long period(4
weeks)of drought.The seedling revival ability
was significantly higher(P<0.05)in caryopses
colected from the SFS than those from the NFS
sites,whereas the seedling revival ability at the
bottom of the canyon showed an intermediate inter-
slope pattern (Fig.3).This result was similar
with results from previous study on barley[5,13],e-
ven on some desert plants[4,14].In areas with peri-
ods of drought during the season with rain,some
plant species have developed adaptations,strate-
gies and mechanisms of seedling drought tolerance
whereby young seedlings may survive after periods
of drought.Plant species of the Poaceae with such
strategies include desert plants such as Schismus
arabicus,from the Saharo-Arabian phytogeograph-
ic region,and Leymus racemosus (Lam.)Tzvel
(wild rye)and Psammochloa villosa (Trin.)Bor.
from the sand desert of the Ordos Plateau of Chi-
na,as wel as Irano-Turanian and Mediterranean
plants,such as Hordeum spontaneum C.Koch
(wild barley)and Triticum dicoccoides (Ascher-
son et Graevner)Aaronsohn (wild wheat)[13-15].
Aridity stress is considered to be a major ecological
factor affecting genetic differentiation of wild bar-
ley at both regional and local levels[19-20].In the re-
cently,Yang et al[21]studied the expression diver-
sity of the drought resistant dehydrin 1 gene
(Dhn1)between the SFS and the NFS ofEvolu-
tion Canyon .The dehydrin gene family belongs
to the leagroup,and it is one of the most studied
drought-inducible gene families.Their study found
that the earlier response of the Dhn1expression
was observed 9hafter dehydration in genotypes
from the SFS,suggesting that the genotypes on
the SFS were indeed more resistant than the sensi-
tive genotypes on the NFS.Therefore,seedling
drought tolerance of H.spontaneum was deter-
mined by adaptive climatic,drought selection pres-
sures.The adaptation of wild barley to drought
environments has accumulated rich adaptive genetic
diversities for drought tolerance in wild barley,
which is an excelent genetic resource for crop im-
provement[22].
Figure 3 Differences in the revival rates of
H.spontaneumseedlings derived from three sites
after exposure to four weeks of drought
2.3 Dormancy depth and revival ability in terms of
drought tolerance
A trade-off between breaking of dormancy of
caryopses and revival ability of young seedlings of
H.spontaneum was found among xeric and mesic
populations at the macro-scale in Israel[13].AtE-
volution Canyon microsite,the effects of various
sites on caryopsis germination and seedling revival
rates were statisticaly significant(P<0.000 01)at
the opposite direction(Fig.4).Thus,dormancy
depth is positively and significantly correlated with
seedling revival ability after drought.Dormancy is
considered to be an ecological adaptation strategy
for coping with natural hazards[3-4,23]. The
caryopses of H.spontaneumfound in xeric areas in
Israel have developed the characteristic of deep
dormancy[3-4,16,18,24].There were the similar results
in the studies on seeds of Psammochloa villosa
(Poaceae)[25]and Brochvpodium distachyon[26].
From a risk avoidance point of view,the longer the
period of dormancy breaking,the higher fitness of
plants exposed to arid environmental conditions,
characterized by highly unpredictable amounts and
distribution of rain[4,16].The trade-off relationship
between the two traits may imply that faster ger-
mination consumes more energy stored in the seeds
and hence the energy left for drought tolerance of
young seedlings is low[13].The general pattern is
that when the environmental conditions to which

第1期 严 俊(等):以色列“进化峡谷”野生二棱大麦种子休眠与幼苗抗旱研究    
wild barley is exposed are more stressful(drier),
the caryopses of the barley reach lower percentages
of germination but their young seedlings have
higher revival ability from drought[5-6,13,15].These
results reveal that the microhabitat environment is
the dominant adaptive factor in the natural selec-
tion for caryopsis germination and seedling drought
tolerance of wild barley,H.spontaneum,and it o-
verrides any inter-slope migration and paralels re-
gional patterns across Israel.
Figure 4 Effect of three sites on caryopses
germination and seedling survival
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(本文审稿:王际睿;责任编辑:巩艳红;英文编辑:李清源)