| Peanut (Arachis hypogaea) is a plant belonging to the genus groundnuts of leguminous family with planting area is second only to rape.As the major oil crops and economic crops in China,peanut has an important role in the protection of the oil supply system,because of its extremely high nutritional value,economic value and utilization value.Currently,the parental origin of 93.75% of all peanut varieties promoted nationwide are ‘fuhuashegn’ and ‘shitouqi’,or a blood relationship that contains them.Peanut varieties cultivated in Henan province are also mainly derived from a small number of backbone parents,resulting in hardly any breakthrough varieties in recent years.Among them,the lack of excellent germplasm resources and excessive dependence on a small number of backbone parental resources is one of the main reasons that restrict the breeding of new varieties.And traditional breeding techniques and existing germplasm resources have made it difficult to improve breeding efficiency.Therefore,excellent new germplasm creation with excellent agronomic traits,strong adaptability,high combining ability and extensive genetic basis is a common concern for scientists and technologists.Peanut cultivars are allotetraploid(2n=4x=40),including two karyotypes,and the wild species of peanut are diploids.Colchicine could prevent the formation of spindle cells from dividing cells,and have no obvious effect on the structure or replication of chromosomes,is the most effective way to double the number of chromosomes.This experiment used peanut seeds as material to study the optimal concentration and time of colchicine treatment,the effect of colchicine treatment on peanut seed germination and plant biological characteristics,and the mechanism of improving drought tolerance of peanut plants in order to obtain peanut polyploidy plants.The polyploid germplasm will be used to improve the practicality and resistance of peanuts,and then lay the foundation for breeding new germplasm of peanut.The results mainly showed 44 that:1.The seeds of ‘Hua 103’ peanut cultivar(2n=4x=40)were treated with different concentrations of colchicine solution at different hours in order to figure out a proper method and obtain polyploids.Correlative model of different colchicine concentrations and time duration was established by soaking seeds,so as to determine the optimum scheme of the polyploid induction of peanut.This study mainly discussed the mutagenic effect of colchicine on peanut seeds with the aim at finding a theoretical and methodical basis for provide better cross parent for breeding of new peanut varieties.With different concentrations of colchicine(0.02%、0.05%、0.1% and 0.2%)on peanut seeds of different time(12、24、36 and 48 h)treatment induced,effects of colchicine concentration and action time of seed germination and the growth development in peanut seedlings were analysed,The results showed that there was significant inhibitory effect of colchicine on germination ratio and growth rate of peanut,and the inhibition was increased by increasing the concentration and action time of colchicine.The results indicated that the optimal concentration and time of induction was obtained by 0.1% colchicine treatment for 36 h with 29.4% induction rate.In colchicine treatment process,the rate of seeds germination was significantly decreased when treated with colchicine at higher concentration and after longer duration.Moreover,the concentration of colchicine had a stronger effect on plantlet regeneration than time duration.2.Based on the experiment of peanut plant induced by different colchicine concentrations,0.1% colchicine treatment was optimum mutagenic concentration.Compared with the normal diploid plants,the polyploid plants induced by 0.1% colchicine treatment were characterized by thicker and stronger roots,stems and leaves.The color of leaves and base of stems were darker and the plants shown slower growth rate.By the comparison of leaf stomatal parameters among different ploidy peanuts,we find that the size of polyploid peanut leaf stomatal size became larger and the stomatal density decreased.After colchicine doubling treatment,chlorophyll and proline contents in plant leaves increased significantly.The plant ploidy was identified by flow cytometry analysis and chromosome counts of the root-tips,the chromosome number of the polyploid plants increased significantly.The results indicated that the polyploid peanut plants could be identified by phenotype,stomas and chromosome number observation and these new materials could be used in breeding of peanut.3.Increasing drought is widely recognized as one of the most severe environmental factors hampering plant survival and productivity.Polyploidy is reported to show enhanced tolerance to environmental stress.In this work,polyploidy plants of peanut were obtained by colchicine treatment.The variant plant induction was achieved by treatment with 0.1% colchicine.Three treatment plants were submitted to well-watered and water-deficit conditions simulated by polyethylene glycol(PEG)stress via a hydroponics experiment,respectively.The results showed that PEG-induced dehydration significantly repressed plants growth,reduced biomass accumulation,inhibited leaf photosynthetic mechanism,and induced membrane lipid peroxidation in plants.After 2 d of withholding water,contents of malondialdehyde were lower in T3 plants compared with T2 plants,while activities of antioxidant enzymes,such as superoxide dismutase,peroxidase and catalase were stimulated and antioxidants were maintained at high concentrations.T3 treatment plants exhibited less growth inhibition,leaf water loss,and chlorophyll reduction than T2 peanut plants.Photosynthesis analysis indicated that T3 plants had much less reductions than T2 plants under water deficit,suggesting that colchicine contribute to improving photosynthetic performance.Physiological analyses revealed that peanut’ tolerance and acclimation to dehydration stress relates to the control of reactive oxygen species and more powerful antioxidant system during water deficiency were found in T3 plants rather than T2 plants.Taken together,these results indicate that colchicine pretreatment contributes to activating a stronger antioxidant defense system and enhancing the drought tolerance of peanut plant. |
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