Pathogenicity And Genetic Differentiation Of Pathogens Causing Banana Bacterial Soft Rot And Resistance Of Musa In Different Growth Periods

Banana bacterial soft rot disease is the most serious threat to banana and has been listed as quarantine object in the list of the People’s Republic of China of the Entry plant quarantine pests. In2009, banana bacterial soft rot disease was firstly discovered in Guangdong province, China. The pathogenic bacteria were identified as Dickeya sp.. At present, most of the researches are focus on the culture characters, physiological and biochemical characteristics and prevention technology of this disease. The research of culture character, genetic differentiation and host resistance at the different growth stages of banana were seldom reported.The pathogenicity of14isolates of Dickeya sp. from zhuhai and nansha districts of Guangdong was analysised by methods of pseudostem inoculation in vitro and seeding pot inoculation. The results showed that the two methods made a consistent result of pathogenic classification, and all the isolates could be divided into three types, severe(++++), strong(+++) and medium(++). The study also indicated that the isolates from the same region showed the similar pathogenicity, and the isolates from different regions exhibited different pathogenicity.The genetic variability of Dickeya sp.were studied based on16S rDNA and housekeeping genes gapA、 MDH of Enterobacteriaceae bacteria, sequence analysis and the16S-23S rDNA internal transcribed spacer PCR (ITS-PCR) and bacterial genome sequence repeat PCR (Rep-PCR) methods. The results showed that14isolates of bacteria have the sequence homology above97%with six typic species of Dickeya, and most of the isolates have the homology over99%. Based on the results of bacterial 16S rDNA, these bacteria isolates can be identified belonging to Dickeya. Using two housekeeping genes, gapA and MDH, the high homology was showed among the most of isolates, and genetic differentiation was showd between isolates of Dickeya sp.. Fourting isolates of Dickeya sp. were divided into6groups by ITS-PCR. Using the degenerate primer pair of Box and J3of bacterial repetitive sequences, the Rep-PCR was completed. The results showed that two genetic groups were generated with the genetic distance of0.52and four groups were generated with the genetic distance of0.65. Therefore, the genetic analysis of14isolates of Dickeya sp. showed that genetic differentiation occurred in banana bacterial soft rot pathogen in GuangDong.The research indicated that Musa showed as a moderate susceptible variety among7leading varieties of banana in our country..Due to the nutritional and economic value of Musa, this research choosed a strong virulent isolate (Xj7-1-4) and inoculated it in Musa at the different stage of growth stage resistance. The results show that the dwarf banana resistance differences in these four stages, and the resistance of seedling resistance in to plants and different.