| Iris L. is one of the largest genera of Iridaceae. The plants are perennial herbs which are more than 300 species in the world, mainly distributed in north temperate regions such as Asia, Europe and North America. There are 64 species, 13 varieties,1subspecies, and 6 forms in China, which is a distribution center of Iris. Iris enjoyed a good reputation for its peculiar flower shapes, gorgeous and plentiful colors in the field of horticultural world. Along with the increase of iris horticultural cultivars, its genetic background is more complex. In this study, 38 different cultivars and species of Iris were selected for the evaluation of genetic diversity and relationship by the morphological marker and ISSR & SRAP. Moreover, some cultivars and species of Iris were selected for the evaluation physiological analysis of high temperature and drought tolerance. The main results are as follows:1. During 29 phenotypic traits of Iris, coefficient of variations are quite differences.By the principal component analysis of phenotypic traits, the results showed that classification based on phenotypic traits, the most important factor is flower character,next is classification by plant types, nutrition organ growth and appendage of petals.On the other hand, contribution of principal component relatively decentralized,accumulation contribution rate growth slowly. It may cause by variables of strong correlation are inadequate concentration, traits belong to multiple species. This indicates that the phenotypic traits of Iris have abundant diversity during the evolution, and it is also the mainly reason of abundant characters variation.2. Both of ISSR and SRAP, the bands were polymorphic(100%), but the number of a detected ISSR bands is higher, each method of polymorphism in PIC values are 1.0,which indicated that the genetic diversity of Iris was rich. Moreover, the conclusion ofgenetic diversity analysis by ISSR or SRAP has high consistency. On the other hand,compare with single molecular marker, multi-molecular markers analysis results more close to the phenotype classification. Mantel verify though genetic distance matrix obtain the result r=0.8052. This shows the combination of two marks method is more reliable, more accurate of presentation of Iris genetic structure. It can also provide a reference of other related researches.3. Recent study shows that there are some obstacles between the hybridization of Iris specie, and the same time, it has very low seeding rate or even fruitless. However, the results showed that Iris‘Gala Madrid’ and Iris‘Nibelungen’ had the longer Genetic distance compare with other I. germanica. Furthermore, they all been clustered with beardless Iris using three kinds of clustering algorithms based on Molecular markers,therefore we assume these two kinds of Iris have Genetic background of beardless Iris highly likely. They could be used to make germplasm innovation of interspecific hybridization advantages parents.4. An experiment was conducted to study the effect of high temperature and drought stress on the antioxidant enzyme activity and non-enzyme substances in ten iris cultivars. Physiological and biochemical indexes, such as activities of peroxidase(POD), superoxide dismutase(SOD), and non-enzyme substances, soluble protein,malondialdehyde(MDA) and proline were tested. The high temperature or drought tolerance of different cultivars of iris was evaluated synthetically by principal component analysis and subordinate function and stepwisemultiple linear regression.The drought tolerance predicting regression equation established by conductivity damage rate(x1), contents of chlorophyll(x3), contents of soluble sugars(x4) and malondialdehyde(x5). The drought tolerance predicting regression equation is D=-439.27+1.744x1+4.913x3+0.5822x4+2.6369x5. The high temperature tolerance predicting regression equation established by activity of SOD(x1) and activity of POD(x2), contents of chlorophyll(x3), contents of soluble protein(x4) and MDA(x5)could be used to evaluate heat tolerance of other iris cultivars. The high temperaturevi tolerance predicting regression equation is D =29.667-0.208x1-2.502x2+0.405x3-1.742 x4-0.036 x5.Based on the drought tolerance predicting regression equation, the result shows that the ranking from highest drought tolerance to the lowest is I.‘Gold boy’,I.‘Tantara’, I.‘Blue Staccato’s Gibeson’, I. germanica, I. confuse, I. sibirica, Iris lactea, I. ‘black knight’, Iris pseudacorus and Iris ensata. The ranking from highest high temperature tolerance to the lowest is Iris ensata, Iris pseudacorus, Iris lactea, I.confuse, I.‘Tantara’, I.‘black knight’, I. ‘Blue Staccato’s Gibeson’, I.‘Gold boy’, I.sibirica and I. Germanica.5.There are existing controversy about the classification of Subgenus Crossiris, in this research, we support it as subgenus of Rodionenko system. On the other hand,after using 3 kinds of clustering methods, it is showed that Iris halophila and Subgenus Linniris clustered into one group. So we suggestd Iris halophila as a Subgenus exist unnecessary, it can be classified to Subgenus Linniri. Iris lactea, Iris pseudacorus, Iris Louisiana all clustered into sub-groups, they have the relatively remote relationship with other Iris, based on their morphologh difference, we suggest divide Subgenus Linniris into some groups.6. Two cultivars of I. ‘Gold Boy’ and I. germanica with high temperature sensitivity and two cultivars of I. ‘Tantara’ and I. ‘black knight’with high temperature tolerance were selected for further analysis. Several physiological responses to high temperatures were investigated, including effects on chlorophyll, antioxidant enzymes,proline and soluble protein content in the leaves of four cultivars. The leaves were sprayed with distilled water, Ca Cl2, or La Cl3. Heat shock factor genes were partially cloned according to the conserved region sequence, and expression changes to high-temperature stress with Ca Cl2 or La Cl3 treatments were thoroughly analyzed.Ca Cl2 slowed the degradation of chlorophyll content and increased proline and soluble protein in I. ‘Gold Boy’ and I. germanica, but had no significant effect on activating peroxidase or superoxide to improve high-temperature tolerance. Geneticexpression of heat shock factor in I. ‘Gold Boy’ and I. germanica, was up-regulated by Ca2+ at later stages of leaf damage under high-temperature stress. La Cl3down-regulated the physiological parameters and expression level of heat shock factor in I. ‘Tantara’ and I. ‘Black Knight’. These results suggest that different I.germanica cultivars have varying high-temperature tolerance, further, that Ca2+regulates their physiological indicators and expression level of heat shock under stress.7. This study examines the tolerance of I. germanica to high-temperature stress;specifically, whether the calcium ion is involved in coordination with other physiological indices including antioxidant contents, chlorophyll, protein content,proline and malondialdehyde, and/or the HSF transcriptional expression during high-temperature stress. Addressing the physiological and molecular mechanisms involved in high temperature tolerance will help researchers develop I. germanica cultivars that can better adapt to climate change. |
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