| The application of allelopathy is an alternative weed control method that could be incorporated into an integrated weed management package, thereby reducing the dependence on herbicides and extending the commercial life of valuable chemicals. Progresses had made in rice allelopathy, but it is also possible to identify a range of researchable areas that still need attention, such as laboratory screening, the mechanism of allelopathy expression under environment stresses, identifying allelochemicals really responsible for weed reduction in the field, searching for the gene involving in rice allelopathy, etc.In this paper, the best bioassay methods was detected by comparing three laboratory screening methods for rice allelopathy, the genetic polymorphism of allelopathic rice was detected by using RAPD and ISSR, then allelochemicals in the leaf extraction and in exudation of rice accessions concerned were identified by GC-MS, at the same time, function proteomic approach was employed to analyze the molecular mechanism of allelopathy in rice induced by the stresses of accompanied weeds barnyargrass (Echinochloa crus-galli L.) .The results were summarized as follows:1 Relay co-cultured with agar (RCA) was significantly different from relay co-cultured with silica (RCS) and cultured with root-exudation (CRE). The average IR of concerned rice on barnyardgrass was 44.0% in RCA, being 91.3% and 86.4% higher than that in RCS and CRE respectively. If a rice accession showing high inhibitory activity on weed in RCA, its average IR in the three screening methods was high. Vice versa. It therefore suggested that RCA could effectively detect the distinct difference in allelopathic potential among rice cultivars tested.2 The considerable variations in allelopathic activity among 57 rice accessions introduced from 10 countries or areas were detected by RCA bioassay method, and five accessions strongly inhibiting the growth of barnyardgrass were characterized. The genetic polymorphism of allelopathic rice detected by RAPD and ISSR approaches indicated that those accessions from the same geographical location were clustered into one group. It was also found that some rice accessions with higher allelopathic potential were clustered together, implying that the genes conferring allelopathy in those rice accessions might be isolocus. However, some rice accessions with different allelopathic potential clustered into the same group performed lower level of generic polymorphism which was attributed to oriented selection for other traits in breeding program.3 The analysis on the substances related to allelopathy showed that the substances de novosynthesized in the tissue of rice were different from those released from rice roots. It was considered that substances released from rice might be decomposed by microbe or reacted biotically and abiotically with the soil prior to interacting with the target weeds. It was inferred that Lemont had lower allelopathic potential than PIS 12777 because of the absence of phenolic acids and the interaction among the substance in the exudation from rice roots.4 The different phenolic acids which were used in orthogonally gyral regression experiment had different impact on root growth inhibition of barnyardgrass. The cinnamic acid had strongly affected the growth of barnyardgrass, while the impact of vanillic acid on 1R was different from the other 4 phenolic acids. Whether the action of a mixture of phenolic acids is additive or antagonistic depends on the concentration of compounds in the mixture. At the low concentration level, the interaction of salicylic and cinnamic acid, salicylic and p-hydrobanzonic acid were additive. At the high level of concentration, the data generally supported the fact of antagonistic activities between them.5 The physiobiochemical mechanism of allelopathic rice under environment stresses was studied in this paper. The result indicated that the activity of PAL in the leaf of PI312777 displayed the trends of growing higher with the increasing of the... |
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