| Iris,a perennial herb of Iridaceae,is one of the famous perennial flowers in the world.It is an ideal plant material for urban greening due to various plant species and flower colors and peculiar flower patterns.China has a wealth of iris germplasm resources,and fully exploiting and utilizing the excellent iris germplasm resources in our country,especially the wild plant resources to speed up the breeding of new varieties is the main direction of the research on germplasm resources of iris in the future.The systematic evaluation of Iris is the basis for further digging the excellent iris germplasm,innovation and seedling growing,and is also the prerequisite for the effective application of iris species in urban landscaping.In this study,some cultivated and wild species of iris in China were used to evaluate the germplasm resources of iris comprehensively and systematically from the aspects of morphology,cytology,physiology and molecular biology.The difference of photosynthetic physiological characteristics and phylogenetic relationship of iris resources were explored and by the analysis of morphological traits,Inter Simple Sequence Repeat(ISSR)and Sequence-Related Amplified Polymorphism(SRAP),their genetic diversity and relationship among iris species(cultivars)were conducted.At the same time,mathematical statistics were used to compare the drought resistance of some iris cultivars and drought-resistant iris resources were screened out.The results were as follows:Firstly,principal component analysis,correlation analysis and cluster analysis were used to investigate the phenotypic characteristics of interspecific and intraspecific iris germplasm resources.The results showed that:27 apparent indexes in 32 iris species or varieties had significant difference,and as could be seen from the principal component analysis results,27 morphological indexes were transformed into five principal components.Compared to other apparent traits,the average coefficient of variation of leaf morphological index was the largest,and the average coefficient of variation of flower internal characters and characters of fruit and seed was smaller,and there was a significant positive correlation between flower diameter,flower height and SW,FW,SL,FL.Based on the genetic distance matrix,32 species(varieties)of iris were divided into three categories by cluster analysis:Iris halophila(Sect.Xyridion Tausch),Iris pseudacorus,Iris lactea Pall(Sect.Limniris Tausch)were divided into one category;20 cultivars of Iris germanica(Sect.Iris)and Iris tectorum(Sect.Crossiris Spach)were grouped into one category;the others were divided into one category.Secondly,the diversity of anatomical characters among iris species was studied by calculating the indexes of stomatal characteristics of 16 species in Iris.The results showed that:The variation of stomatal number and stomatal density was largest in different iris species,and the variation of stomatal width was the least.The stomatal indexes in 16 iris species showed significant differences.By cluster analysis,16 iris species were divided into four categories:The first category included Iris germanica and Iris tectorum;Iris ruthenica,Iris uniflora,were clustered into the second category;The third category included Iris mandshurica,Iris tigridia,Iris scariosa;The others were divided into fourth category.Thirdly,Scanning electron microscope(SEM)was used to observe the normal pollen of representative species of five iris subgenus and the morphological indexes of pollen were determined.Based on the cluster analysis,the genetic relationship of five iris varieties was analyzed.The results showed that:Iris tectorum had the largest pollen grains with the longest polar axis and the equatorial axis.The obviously prominent cristae with less bifurcation on pollen grains' surface were relatively wide and there were the largest distance of cristae and the least density of cristae on pollen grains' surface,while the Iris halophila had the opposite morphology of pollen and parameters of cristae.The five kinds of pollens had wrinkled ornamentation of ditch form,with only one germinal furrow.Except Iris halophila,other iris species had verrucous particles of different sizes and quantities distributed within cristae on the surface of pollen grains.By cluster analysis the five kinds of iris were divided into three categories:The first category included Iris germanica,Iris tectorum,and Iris dichotoma.Iris halophila and Iris lactea were clustered into one category separately.And the first category could be divided into two groups.The first group included Iris germanica and Iris tectorum,Iris dichotoma was grouped into the second group individually.Fourthly,diurnal variation of photosynthetic and fluorescence parameters of representative species of five iris subgenus were measured by LI-6400 and CF Imager,and the physiological and ecological characteristics and differences of photosynthesis were studied.The results showed that:The diurnal variations of Pn in Iris germanica,Iris tectorum,Iris dichotoma and Iris uniflora showed 'double peak'curve.However,the Pn value of the first three iris species recovered slightly in the afternoon,and the photosynthetic 'lunch break' phenomenon was more serious.As could be seen from the diurnal variation of fluorescence parameters,Iris tectorum and Iris uniflora had a higher value of ?PSII at noon than other iris species,and the Fv/Fm value was smaller than that of other iris species.The higher NPQ was still not enough to disperse the absorbed excess light energy and the degree of light suppression was heavier.Fifthly,by analyzing and comparing the numbers of chromosome and karyotypes of representative species of five iris subgenus the differences of karyotype was studied and evolutionary relationships was speculated.The results showed that:As.K and MAR of five iris species showed the trend of 'bidirectional increase',among which MAR and As.K of Iris germanica were the highest,followed by Iris halophila,and MAR and As.K of Iris dichotoma were the lowest.Compared with other iris species Iris dichotoma had the lowest values of LR and MAR.Also it had been found that iris materials showed two kinds of increasing trends.Among them,Iris tectorum and Iris pseudacorus increased faster in the direction of LR,while the Iris germanica and Iris halophila increased faster in the direction of MAR.Sixthly,the pot experiment was conducted to investigate the physiological and biochemical indexes of iris cultivars under continuous drought stress.The drought resistance of iris materials was evaluated and the indexes which could evaluate the drought resistance of iris varieties better were screened out by mathematical statistical analysis.The results showed that:10 iris varieties could be sequenced in the following order according to the levels of drought resistance:'Purple Flower'>'Bloodstone'>'Tawny'>'Golden Baby'>'Bronze Red'>'Navigation Banner'>'Adventure'>'Dwarf Dream'>'Purple Glow'>'White Calyx'.Based on the cluster analysis,10 iris cultivars were divided into three groups namely drought-resistance group,medium drought-resistance group,and low drought-resistance group.Of these,'Purple Flower' and 'Bloodstone' were clustered in the drought-resistance group,demonstrating that they had the highest drought-resistance capability.Meanwhile,the results of stepwise regression analysis showed that POD activity and RWL,MDA could be used as important indexes for the comprehensive evaluation of the drought resistance of the iris cultivars,and drought resistance of iris cultivars could be evaluated using regression formula in general.Seventhly,The ISSR and SRAP molecular markers were used to analyze the genetic diversity of 26 iris cultivars,and the genetic relationship among iris cultivars was studied by the cluster analysis.The results showed that:The polymorphism percentage of ISSR markers was 89.47%,while the polymorphism percentage of SRAP markers reached 96.54%.The results of cluster analysis indicated that the ISSR marker could classify the morphological similar cultivars to a certain extent,and SRAP marker could also make the same species from different regions first cluster into one group on the basis of classifying the similar phenotypic iris varieties,indicating that the SRAP marker used to analyze the genetic diversity of iris cultivars were more accurate than the ISSR marker.However,the results of cluster analysis of ISSR and SRAP not only classified iris species with similar phenotypes,but also isolated two iris species from Shanxi province.It had also been found that Iris germanica 'Bronze Red',Iris germanica 'Indian leader'were clustered into one group and Iris germanica 'Purple Glow',Iris germanica 'White Calyx',Iris germanica 'Black Banner' were gathered together in three kinds of clustering methods,indicating that these varieties had very close relationship. |
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