Selecting The Predominant Pathogeny Of Soft Rot And AFLP Marking Of The Resistant Gene In Chinese Cabbage

Chinese cabbage(Brassica rapa L.ssp.pekinensis) originated from China, and is one of the main vegetables in Asia,especially in east-Asia.These years with the development of protected-cultivation technique,continuous cropping is very common,which made the emergency and development of Chinese cabbage soft rot(CCSR) trending rising and cause great loss to the production. Erwinia carotovora is the main pathogeny of soft rot in Chinese cabbage, Erwinia.Carotovora subsp.carotovora(Ecc) is the predominant strain,and it often co-infected with other strains.Now resistantance to soft rot is one of the most important breeding goals of Chinese cabbage.While classic parent materials selsction have to suffer a lot of time procedures and is susceptible to the environment,but by selecting the predominant pathogeny,inoculating and identifying the typical susceptible materials and the resistant ones and marking the anti-CCSR gene can facilitate the selsection of CCSR resistant materials and speed up breeding procedure.Susceptible material 1042 and resistant one 683 were availbale by inoculating the selscted predominant pathogenic strain Erwinia.Carotovora subsp,carotovora.,then the F2 of 683 and 1042 were obtained.By inoculating and according to the method of bulked segregation analysis(BSA) three susceptible and resistant gene pools were constructed to select the AFLP markers tightly linked to the resistant gene.The results are describled below:1.Clected 60 infected samples in chinese cabbage field of Jinan,Qingdao,Weifang,Yantai,Dezhou and Linyi.We obtained 143 strains by isolating,purifying and pathological determinating.2.physiological and biochemical measuring showed that there are four types Erwinia carotovora in the 143 strains,they are Ecc,Eca,Ecw,Ech,their emergence frequency in the field are 70%,11.1%,0.6%and 19.3%respectively, and Ecc is the predominant strain.3.After inoculation with Ecc,each individual of the F₂ population was classified as resistant or susceptible by the method of visual observation. According to the result of identification,the practical ratio of resistant individuals to susceptible individuals was 1:3.17 in the F₂ population,It is in accordance with the ratio of 1:3.Resistance to soft rot in this population is controlled by a pair of recessive gene.4.Three pairs of different resistant pools and susceptible pools were constructed with the preamplification product of the most resistant individuals and the most susceptible individuals.Total 64 pairs of primer combinations which consisted of 8 EcoRI primers and 8 MseI primers were used to screen the AFLP marker by BSA method,As a result we identifed one AFLP molecular markers linked to soft rot susceptible gene.Silver blot showing that the fragment is about 150bp and it stablely existed in each individual of the F₂ population.