Biological Evaluation And Prediction Of Powdery Mildew Resistence On Red Clover After Neutron Radiation

Via studying the effects of neutron radiation on seed germination, seedling growth characteristics, root tip cells, agronomy characteristics, physiological and biochemical indexes of Trifolium pratense cv. Minshan. Main results were as follows:1. Germination rate were positively correlated with radiation dosage, and root length and bud length were negatively correlated with radiation dosage, while the radiation dosage was from 0 to 58.386 Gy. Lower dosage (11.01 to 29.31Gy) promoted root length, germination rate and plant height; Higher dosage (>29.31Gy) promoted seed germination and bud length, but prohibited seedling rate and plant height. 29.31Gy was the most suitable dosage for seed germination and seeding growth Minshan red clover.2. Mutation types, such as micro-nuclear, small nuclear, nuclear budding and nuclear distortion etc appeared. Mutation types, such as dual-core, nuclear budding and nuclear sag also appeared in a few cells. Fast neutron radiation had significant effect on root tip nuclei of red clover, lower dosage (<11.01Gy) had promoting and stimulating effect on root tip mitosis of red clover; higher dosage (> 58.386Gy) had a certain inhibition on mitosis of radicle tip cells, affected the internal structure of nuclear, chromosomal and DNA genetic material, and ultimately inhibited seed germination and growth.3. Fast neutron radiation had a certain effect on growth stage and growing period of red clover. Along with the increasing of radiation dosage, growth stage delayed and growing period increased, while the dosage was from 17.704Gy to 58.386Gy.4. After being radiated with different dosage of fast neutron, natural plant height at different growth stages reduced at a certain degree, and reduction degree increased with the ncreasing of radiation dosage. Lower dosage (11.01 to 17.704Gy) was helpful for the increasing of natural plant of seedling, but higher dosage (≥29.31Gy) inhibited the normal growth of plants. During the entire growing period, absolute plant height decreased with the increasing of radiation dosage. Radiation had any effectes on shooting structure of red clover. Normal plants (with no radiation) were prostrate, but they showed half prostrate and vertical structure strong while radiated. 5 Lower radiation dosage (11.01 to 29.31Gy) promoted branching of red clover, but higher radiation dosage prohibited branching strongly.6 Studies showed that chlorophyll a content in leaf of red clover was significantly negatively correlated with disease resistence. The lower the content, the stronger the resistence was. Fast neutron radiation inhibited the synthesis ability of chlorophyll a in red clover seedlings, their chlorophyll a content were lower than the control. Fast neutron radiation promoted the synthesis ability of chlorophyll b in red clover seedlings, and so their absorbing ability to weaker and scattering light improved. Total chlorophyll content in each treatment was lower than the control to a certain degree, and with the increasing of radiation dosage, total chlorophyll content decreased gradually. The ratio of Chla to Chlb was lower than the control. Results of this experiment showed that fast neutron radiation was useful for improving the performance of red clover to resist on powdery mildew.7 Fast neutron radiations had certain destructive effect on the biomembrane of red clover seedling and made MDA content increased. The most serious demage occurred in higher dosage, and it led to peroxidation.8 Free proline contents in red clover had any relation with with the resistance to powdery mildew. Radiation activated the defense responsing system of red clover; it was useful for the formation of systemic resistance and increasing of disease resistance. Free proline content increased after fast radiation, and with the increasing of radiation dosage, free proline content increased.9 Low dosages (0 ~ 11.01Gy) could improve the osmotic adjustment ability of red clover, it made the soluble sugar content in seedlings increased, promoted its germination and growth, and it was useful for increasing the resistance to powdery mildew.10 Studies shown that soluble proteins in plants had any correlation with disease resistance and protein content in resistant types was lower than the susceptible types. After fast neutron radiation, protein content in red clover leaf declined. With the increasing of radiation dosage, decreasing degree of soluble protein content increased gradually. This result showed that fast neutron radiation was useful for enhancing soluble protein structure, improving protease activity and enhancing disease resistance indirectly.11 It was useful for biochemical marker via POD zymography analysis on extraction from root, stem and cotyledon of red clover and among different dosages. It could provide a theoretical basis for breeding variety resisting to powdery mildew and studying disease resisting mechanism of red clover.