| Rice bacterial blight(BB)has been a worldwide disease caused by gram-negative bacterium Xanthomonas oryzae pv.Oryzae(Xoo),which easily broke out in high temperature and high humidity environment,and severely affected the production of rice in southern areas of China.Many studies have shown that one of the effective of methods to prevent bacterial blight was to cultivate and plant rice varieties containing a broad-spectrum disease resistance gene or a combination of multiple disease resistance genes.Shanlan upland rice is a general name for a series of endemic varieties which has special agronomic characteristics.Under the traditional drying cultivation method the yield was lower,while under flooding cultivation,the yield increased significantly compared to drying cultivation method.Bacterial blight was not easy to spread under the drying cultivation method,but when cultivated under flooding cultivation method,bacterial blight spread easily and quickly.In order to explore the characteristics of Shanlan upland rice’s resistance to rice bacterial blight,17 varieties of Shanlan upland rice were used as materials and planted in the field and greenhouse with flooding and drying cultivation methods at the same time in this experiment.The functional marker method was used to detect its resistance genes.In the field,the resistance of Shanlan upland rice to Haikou local races of BB was observed and the yield was measured under flooding and drying cultivation methods.In the greenhouse,the resistance of Shanlan upland rice to 2 Philippine races of BB,PXO99(P6)and PXO145(P7),was evaluated under two cultivation methods,and the leaf length-width ratio and vascular bundle structure were observed under different cultivation methods.Finally,the various factors affecting Shanlan upland rice’s resistance to BB were analyzed.The result of this study will provide theoretical foundation for detecting effective bacterial blight resistant genes and choosing proper rice varieties and cultivation method.The research result was as following.(1)The results showed that the total disease index of 17 varieties in flooding cultivation method was 50.75 higher than that under drying cultivation condition in the field during the tillering stage.12 species of varieties showed higher bacterial blight disease index under flooding cultivation method than that under drying cultivation method in the field.Nevertheless,the total yield under flooding cultivation method was 3.05% higher than that under drying cultivation mode.(2)In the greenhouse,2 Philippine races of BB were inoculated to 17 species of varieties of Shanlan upland rice in the early tillering stage.After inoculating 17 varieties with P6,only 1 variety showed resistance,8 varieties showed medium resistance and 8 varieties were susceptible under flooding cultivation,while 2 varieties were resistant and 3 varieties showed susceptibility under drying cultivation method.After inoculation with P7,7 varieties showed resistance and 2 were susceptible under flooding cultivation method.And 9 varieties showed resistance and only 1 was susceptible under drying cultivation.The resistance was affected by different cultivation methods and the resistance was stronger under drying cultivation condition than that flooding cultivation condition.Most varieties had stronger resistance to P7 than to P6.(3)Combined with molecular markers which tightly linked to the resistance gene cloned to analyze 17 Shanlan upland rice varieties,the result showed that 16 varieties contained Xa1 gene and 5 varieties contained Xa27 gene.However,all varieties did not contain resistance genes xa13 and Xa21.Different varieties had resistance to bacterial blight to different degree.However,the Changshanmanuo which contained no above-metioned resistant gene had good resistance.It was speculated that this variety contained undetected resistance genes of rice bacterial blight.(4)The leaf length-width ratio measured in the greenhouse was only positively correlated with the resistance after inoculation with P7 in drying cultivation.The varieties with slender leaves had stronger resistance to P7 in drying cultivation.However,the leaf length-width ratio was not related to the resistance to P7 during flooding cultivation and the resistance to P6 under the two cultivation modes.The lengthwidth ratio was not correlated with resistance to P6 under two cultivation methods.(5)Malondialdehyde(MDA)was related to resistance.4 varieties were chosed to measure.Before inoculating P6,the MDA content was low in leaves and MDA content was lower under flooding cultivation than that under drying cultivation.After inoculating P6,the MDA content of leaves got higher under drying cultivation and it rose faster than that under the flooding cultivation method. |
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