Isolation And Identification Of Pathogen Causing Root Rot Of Caladium Bicolor And The Transformation Of Broad-Spectrum Resistance Gene AtNPR1

As an ornamental plant,Caladium bicolor has metamorphic tubers.It is famous for broad leaves,bright colors and various shapes.Caladium bicolor is vulnerable to root rot caused by pathogen in the field,leading to the harm of the plants and the decrease of the yield.Temperature and humidity are the important occurrence factors of root rot disease.Chongqing has a high temperature and humidity in the late spring or early summer,it is the key factor influence the safy of Caladium bicolor.In this paper,these problems were discussed for the introduction of Caladium bicolor in Chongqing.First we observed the symptoms of root rot on Caladium bicolor,and identified the pathogen of the disease;Second the transformation conditions of Caladium bicolor was optimized,then the AtNPR1 gene was drived into Caladium bicolor in order to enhance the plant resistance.The main results of this study are as follows:1.The symptoms of root rot disease on Caladium bicolor.Root rot of Caladium bicolor disease occured in April became severity from May to June.The symptoms of the overground parts: It was found that the leaves become yellow with brown necrosis spots and the petioles bend outwards;As the disease developing,the leaves became wilting from outside to inside and the new leaves growed slowly.The symptoms of the underground parts: first,the spot occurred on the base of the rhizome,and then the roots and stem rotted with the colour of brown.2.Isolation and identification of pathogen of root rot disease on Caladium bicolor.The pathogens were obtained through the routine separation in the affected parts.Then thry were proved the pathogen of the root rot disease on Caladium bicolor according to Koch’s rule.After that the pathogens were identified as Rhizoctonia solani AG4 fusion flora according to morphological characteristic and rDNA-ITS gene sequence analysis.3.The genetic transformation system of Caladium bicolor was optimized.The leaves of Caladium bicolor were put on different concentrations of Kanmycin to choose a suitable concentration for screening,the Kanmycin concentrations are determined to be 150 mg/L;The leaves were treated with different treatment methods to choose a suitable way for regenerating,the treatment method was determined to be 0.05 MPa with 15 min to regenerate.4.The transgenic plants were obtained.A total of the 500 leaves of Caladium bicolor were transformed with AtNPR1 gene using the optimized genetic transformation system.A total 120 resistant plants were obtained.And there were 29 PCR positive plants,the transformation percentage was 5.8%.At the same time,eleven of the PCR positive plants can be stained blue through GUS tissue staining.The transgenic plants were obtained.5.The growth situation of transgenic plants.We found that some of transgenic plants grow up slower than the wild-type,but there were no other changes in biological6.Evaluation of disease resistance of transgenic plants.The transgenic plants showed different resistance to Rhizoctonia solani,and three of them showed significant resistance.