Studies On Effects And Physiological Mechanism Of Male Sterility Induced By Chemical Herbicides In Brassica Napus L.

Rapeseed, one of the most successfully heterosis-utilized crops, is the second most important oil crop in the world. At present, the main approaches of heterosis utilization in rapeseed consisted of cytoplasmic male sterility, nuclear male sterility, self incompatibility and utilization of chemical hybridizing (CH). Chemical hybridizing way, with more flexibility in parental choice, much shorter time in breeding cycle, higher male sterile rate (100%), has become a hot spot in heterosis utilization of rapeseed breeding. However, the key to use the CH successfully is to screen out the excellent chemical reagent. In this study, the effects on male sterility of rapessed(Brassica napus L.) induced by four chemicals (tribenuron-methyl, flumetsulam, quizalofoppethyl and nicosulfuron) were determined. The chemical hybridizing agent—tribenuron-methyl utilized on Brassica napus L. from Si-chuan region was preliminarily selected as the most effective one; Further, the influences on flower morphology, agronomic characters and male sterility induced by different concentrations and doses of tribenuron-methyl, the timing of spraying and frequency of spraying were determined respectively; Meanwhile, tribenuron-methyl added with washing powder, acetochlor, pyrazosulfuronethyl and indole butyric acid(IBA) respectively, was determined and effective combinations on male sterility were screened out. The main research results were as follows:1. Sulfonylurea herbicide tribenuron-methyl was screened out with the best effect of inducing male sterility both spraying on the leaf and smearing onto the stem in Brassica napus L.; while the other three kinds of chemicals had no effect on male sterility in this experiment when the concentration of flumetsulam was lower than1.0μg/mL, or the concentrations of quizalofoppethyl and nicosulfuron were lower than5.0μg/mL respectively.2.0.30μg/mL tribenuron-methyl was sprayed onto leaves of rape in bolting period with1.5-2mm length bud, and the second spraying was about10days later, and8-10mL solution per plant, making the sterile plants rate more than90%;15-20mL solution was sprayed on per plant, and0.05μg/mL-0.10μg/mL tribenuron-methyl could induce100%of sterility plant rate and no phytotoxicity, achieving the whole flowering infertility.0.30μg/mL tribenuron-methyl smeared onto the stem twice induced91.16%of full sterility plant rate,100%of sterility plant rate, and the sterile period lasted for25days. The spraying of tribenuron-methyl were best utilized when the length of bud was1.5-2mm (microspore mononuclear period) or3-4mm in Brassica napus L. Full sterility plant rate reached100%in the plants sprayed on the leaves only once by0.15μg/mL tribenuron-methyl with0.2%-0.5%washing powder,0.30μg/mL tribenuron-methyl with0.02%acetochlor, or0.30μg/mL tribenuron-methyl with0.30μg/mL pyrazosulfuronethyl respectively when the length of bud was1.5-2mm and there was no obvious phytotoxicity; However, plants induced by tribenuron-methyl with IBA promoted fertile pollen grains production unexpectedly. All the four chemicals blended with0.15μg/mL and0.30μg/mL tribenuron-methyl sprayed on the leaves twice resulted in very obvious phytotoxicity.3. After0.30μg/mL tribenuron-methyl induction, the length of filament of99-35was decreased from8.04mm to2.87mm, and the length of filament of09QB48-54was decreased from7.84mm to3.42mm. Filament length variations were significant between the plants with and without tribenuron-methyl induction; but corolla diameter, anther length, pistil length, petal length or petal width showed no significant difference between the plants with and without tribenuron-methyl induction.4. Along with the increasing concentration of tribenuron-methyl, plant height, main inflorescence length, the number of primary branches, the number of siliques of main sequence, the number of total siliques gradually reduced, in other words, they were negatively correlative with the concentration of tribenuron-methyl.0.05μg/mL tribenuron-methyl induced100%of sterility plant rate, agronomic characters of plants induced by tribenuron-methyl and CK were not significantly different; the seeds setting percentage was not basically affected; and the main agronomic traits also showed very obvious phytotoxicity symptoms after tribcnuron-methyl treatment (0.15μg/mL and above).5. After different concentration of tribenuron-methyl induction, soluble protein content in leaves and buds of Brassica napus L. were almost lower than CK; POD enzyme activity were higher than those of CK. Free proline content and SOD enzyme activity in leaves were both lower than CK at the8th day, but at the13th or21th day, the variations seemed irregular. As to the buds, free proline content was higher than those of CK, and SOD enzyme activity was lower than CK at the8th day; but both free prolinc and SOD enzyme activity were higher than those of CK at the13th or21th day.