| Banana is a typical tropical and subtropical fruit trees, which are widely distributed in tropical and southern subtropical regions. China is one of the world’s major banana producing countries. The banana has a wide range in Guangdong, Hainan, Guangxi, Fujian, Yunnan and Taiwan Province. In recent years, due to changes in climate conditions, the banana industry in Guangdong, Guangxi, Yunnan Province suffered serious chilling threat resulting in the yield and economic loss for the majority of growers. Although some preventive measures against cold damage were established, the results indicated that these measures have a small effect. Therefore banana breeding is a fundamental way to solve the chilling problem of banana. Currently, the major production cultivar of bananas is triploid which can not be to develop new varieties through traditional cross-breeding due to its high level of sterility. The seed degradation and resistance of the existing cultivars are decreased by prolonged intensive cultivation. Radiation mutagenesis technique becomes an important way for creating new banana germplasms and varieties.In this study, regenerative callus and buds of immature male flowers from banana were as explant material to induce mutation by 60Co-γ ray and then screened by low temperature selection (14,10,7,4℃) to obtain a significant mutant resistant to chilling. The mechanism of new chilling germplasm was explored by morphology observation, physiological and biochemical index determination and SSR molecular markers.The reaserch will provide a foundation for future new banana germplasms and varieties. The main results are as follows:1. Five types (40GY,60GY,70GY,80GY,100GY) of radiation doseon were used regeneration explant of immature male flowers from banana. Bud vitality and stress resistance are seriously affected by 80GY and 100GY treatment according to the germination condition under room temperature, the buds number under low temperature, the number and growth of regenerated plants. However, survival buds regenerated plants by 70GY treatment showed good resistance to cold demage under low temperature. This result indicated that 70GY radiation dose is a relatively ideal dosage to obtain bananas chilling mutation.2. Radiation mutagenesis explants (callus and buds) from differentiated seedlings at room temperature exhibit a different damage status at different temperatures. The average chilling injury level appeared a turning points from slow growth to rapid growth under 4℃ stress 3d to 5d. This indicates that banana seedling leaves were damaged greatly at 4℃, so the screening temperature of plantlet to cold tolerance is 4 ℃.3.420 seedlings among buds and tissue culture plantlets after low temperature screening have preliminary cold resistance including 62 seedlings showed good resistance to cold by phenotype analysis.224 plants regenerated after hardening and transplanting were obtained. Survival rate of those was only 51.47%, while the survival rate of control seedlings was 98.67%.4. The growth rate of banana cold tolerance seedlings is lower than that of the control seedlings. Phenotype analysis showed that size, number and high of leaves, plant are smaller than that of the control.5.12 of 40 pairs SSR polymorphic primers were suitable screening for cold tolerance mutant validation,16 selected plants were divided into three categories through cluster analysis. The result suggested that the mutant No.1 had larger variation based on DNA analysis level.6. Cold tolerance seedlings showed strong resistance ability to low temperature and some important physiological indicators of those changed significantly. The POD, CAT activity of the cold tolerance seedlings were significantly higher than that of the control, while the content of MDA of the cold tolerance seedlings was significantly lower than that of the control during low-temperature stress. |
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