Study On Heat-resistant Somaclonal Variants Of Tea-applied Chrysanthemum

Tea-applied chrysanthemum is popular, for it not only has special value on drinking but also has precious value on medicine. Tea-applied chrysanthemum can well grow under warm and cold climate but can not stand high temperature. Its optimum growing temperature is 18～21℃. In Wuhan, temperature in summer often reach above 38℃, and this high temperature can directly or indirectly affect the physiological and biochemical metabolism of tea-applied chrysanthemum, thus inhibiting the growth and development of tea-applied chrysanthemum and hampering its introduction, cultivation and promotion severely. As the continued effectiveness of tea-applied chrysanthemum is validated, the marketing demand of quantity and quality is increasing. As a result, tea-applied chrysanthemum with traditional breeding methods can not meet the needs in producing and living. In this experiment, Chrysanthemum morifolium cv Hangbaiju, Chrysanthemum morifolium cv Boju, Chrysanthemum morifolium cv Gongju, Chrysanthemum morifolium cv Shennongxiangju, four kinds of chrysanthemum were chosen as materials, their lethal temperature and heat resistance were explored. Meanwhile, in order to obtain new varieties of heat resistant chrysanthemum, the study combined heat stress and osmotic stress methods to select heat resistant chrysanthemum somaclonal variants in vitro. The main results and conclusions are as follows:1. Lethal temperature and heat resistance of tea-applied chrysanthemum.After a series of graded trials under heat stress, conductance measurement and analysis was done on open field and tissue culture seedlings of the four kinds of tea-applied chrysanthemum, it is discovered that the relation between temperature and cell injury rate showed typical "S" curve through significant verification. Half-lethal temperature LT50 was determined by high-temperature inflection point through logistic equation, the order of half-lethal temperature under heat stress of open field seedlings of those four kinds of chrysanthemum is:Chrysanthemum morifolium cv Shennongxiangju51.83℃, Chrysanthemum morifolium cv Hangbaiju51.39℃, Chysanthemum morifolium cv Boju57.00℃, Chrysanthemum morifolium cv Gongju55.67℃,; the order of half-lethal temperature under heat stress of tissue culture seedlings of those four kinds of chrysanthemum is:Chrysanthemum morifolium cv Shennongxiangju44.37℃, Chysanthemum morifolium cv. Hangbaiju47.83℃, Chrysanthemum morifolium cv Boju47.57℃, Chrysanthemum morifolium cv Gongju46.09℃,. The order of heat resistance strength of open field and tissue culture seedlings of those four kinds chrysanthemum are the same, the order of heat resistance is:H>B>G>S.2.In vitro selection of the heat-resistant somaclonal variants in tea-applied chrysanthemum.When stress temperature is 36℃, the time reaching half-lethality is 15d and the concentration of exogenous SA is 1mg/L, browning rate of the four kinds of tea-applied chrysanthemum was the lowest,37.33%,48.00%,57.33%,66.67% respectively.When stress temperature is 38℃, the time reaching half-lethality is 9d, and the concentration of exogenous SA is 1mg/L, browning rate of the four kinds of tea-applied chrysanthemum was the lowest,32%,45.33%,65.33%,70.67% respectively. Compared with 36℃,38℃and 40℃heat stress treatment,40℃selection presses too much, while 38℃heat treatment takes shorter time to achieve half-lethality than 36℃, which not only saves time but also avoid physiological and biochemical adaptation due to low stress and long incubation time. Therefore, in order to allow operating and controlling of selection in vitro conveniently, to improve the efficiency of selection and to obtain the true heat-resistant variant,38℃is appropriate as stress temperature to select heat-resistant variants of tea-applied chrysanthemum which is more suitable for cultivation and growth in high-temperature region,9d is the appropriate time, and a concentration of lmg/L of salicylic acid is the appropriate selection pressure.38℃high temperature stress combined with the concentration of 1 mg/L of salicylic acid osmotic stress of the material after processing 9d can be used as indicators of selection in vitro.Using four kinds of aseptic tea-applied chrysanthemum's leaves as explants, in the induction and differentiation medium containing a concentration of 1mg/L of SA,25℃incubation for 2d, and then placed them under 38℃heat stress for 9d, and then transferred materials to non-SA inducing and differentiation medium for three weeks, temperature should be set to 25℃. No variants of H and S appeared.B access to selected Department of variant plants B1,B2,B3,G was selected variant plants obtained Department of G1,G2.3. Initial identification of heat-resistant somaclonal variants. Under room temperature and high temperature conditions, the proline content, SOD activity and MDA content in variants had significant differences from wild species. The free proline content and SOD activity are higher in variants than in wild species, while MDA content decreased in variants compared with wild species. Through comparison of variants and wild species in proline content, SOD activity and MDA content in trends and patterns of variation, it shows that variants are better heat resistant.