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Physiological and Genetical Studies on Bacterial Blight (Xanthomonas oryzae pv. oryzae) Resistance in Rice (Oryza sativa L.)
白葉枯病之反應情形，結果發現施用高濃度矽肥(150 ppm) 可使感病
The thesis explored mainly the effect of nutrients on the biochemical and physiological characteristics associated with, and the genetic studies of bacterial blight resistance in rice (Oryza sativa L.). The rice materials included susceptible variety such as TN1 TCS10, TC189, and TNG67, and resistant variety (strain) such as TCSW1, TSWY1157, TSWY7, and TKY6287. The clipping inoculation methods of Kauffman et al. (1973) was adopted to evaluate the resistance performance of test rices using the XM42 and XF13 strains of Xanthomonas oryzae pv. oryzae as challenging pathogen. The results obtained are summsrized as follows : 1. Under the hydroponic culture system, the application of silicate at 150 ppm, on the contrarily, greatly enhanced the resistance of both TSWY7 and TN1 plants. An adjunct chemical analysis during the investigation revealed that the enhansive effect of silicate application was clearly associated with the increases of silicon and the decrease of soluble sugar contents among tested rices. 2. In order to explore the physiological characteristics associated with bacterial blight resistance, seedlings of both TSWY7 and TN1 plants were grown by hydroponic culture in a growth chamber as a model system for the resistance evaluation. Artificial inoculation of TSWY7 plants with the XF13 strain of this pathogen generally led to an enhanced rate of ethylene production throughout a four days experimental period. Where plant, the enhancement of pathogenesis related ethylene production was not observed. In accompany with the increased ethylene production, continued increase of peroxidase activity was detected from the soluble protein contents of the XF13 pathogen inoculated TSWY7 plants for 4 days after inoculation. And likewise, the enhanced peroxidase activity was not observed in the compared TN1 plants. 3. In order to explore the genetic behavior of bacterial blight resistance among the Indica and Japonica rices, two sets of diallel crosses were undertaken in which 5 Indica rices (namely TN1, TCS10, TCSW1, TSWY7 and TSWY1157) and 4 Japonica rices (namely TC189, TNG67, TN5 and TKY6287) were used. The disease resistance performance of their F1 progenies were evaluated by challenge inoculation with the XF13 and XM42 strains of X. oryzae pv. oryzae by the clipping method in both greenhouse and field trials. In addition to the diallel crosses, backcrosses were also conducted among two sets of Indica rice crosses (TN1TSWY7, TN1TSWY1157) and two sets of Japonica rice crosses (TKY6287TC189, TKY6287TNG67). The P1, P2, F1, F2, BC1 and BC2 backcrosses progenies were likewise evaluated for their bacterial blight resistance both in greenhouse and field trials as stated above. The resistance performance of all tested rice plants were determined by lesion lengths developed 14 days (for greenhouse trial) or 21 days (for field trial) after artificial inoculation. Statistic analysis of the results obtained from both the diallel crosses trial and the backcrosses trial generally indicated that the resistance of tested rice strains were characteristic of incomplete dominance. The additive and dominance effects both appeared to be significant for the two types of rice varieties tested; and among them, the additive effect was evidently greater than the dominance effect. The heritability of the resistance characteristic was over 80 % in all diallel crosses tested; the maternal effect was clearly not involved. The data obtained from generation mean analysis indicated that the continuous distribution of disease resistance among the F2 progenies of both types test rices were positively skewed. Morever, the disease resistance among the F2 appeared to be confered by genes in a multiplicative way in which the additive and dominance effect were of great importance.
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