Genetic Relationship Identification Of Citron Germplasms Based On Resistance Of Citrus Canker

Citron C-05(Citrus medica L.)is,up to now,the unique citrus genotype identified resistant to citrus canker.This study analyzed the effects of 3 different resuspending buffers on the proliferation of Xcc in different growth periods.The selected resuspending buffer and the appropriate growth period of artificial inoculation Xcc,and accurately evaluated the citron germplasms and its hybrids resistance of citrus canker.It provides the basis for citron germplasms and its hybrids resistance response.The inoculation in vivo was used to further study the disease resistance of the 65 strains of ‘Shatian’ pummelo and Citron C-05 hybrids obtained in the previous period.As genetic diversity exists among different citron genotypes,and diversity may relate to the resistance to the canker disease.It is not clear if there is the relationship between the phylogeny and the degree of resistance to citrus canker.In this study,3 molecular markers were used to analyze the genetic diversity of 14 citrus germplasms and 4 control materials.The phylogenetic relationship between Citron C-05 and other citrus germplasms was identified through analysis.It provides reference for the resistance analysis of citrus canker and further analysis of the resistance mechanism of Citron C-05.The main results are as follows:(1)The optimal buffer and growth period of inoculated Xcc were compared and analyzed.10 mmol Mg SO4 as the best resuspension solution to maintain the activity of Xcc to the greatest extent.To ensure the accuracy of inoculation concentration,inoculation OD600=0.62 With OD600=0.30 as the best growth period,the inoculation should be completed within 4 hours of placement time,and the test duration exceeds 4 hours.Sterile water can be used to resuspend the bacterial solution.(2)According to the analysis of relative resistance index,65 offsprings of Shatian pummelo and Citron C-05 extremely resistant hybrid offspring identified in vitro were inoculated in vivo to further determine their disease resistance.According to the analysis of disease resistance index and morbidity,it is found that there are still types of extremely susceptible diseases,and the area ratio of the lateral veins of the lesions reaches 30-40%.The symptoms are similar to that of Bingtang orange.the resistant type was lower than that of the male parent Citron C-05.(3)Among SRAP and SSR markers,65 special markers unique to single genotype were chosen.American citron and common citron,which have the closest relationship with Citron C-05,show disease resistance,indicating that the relationship between citron and citrus canker disease has a certain correlation.(4)Taken into account of all the three types of molecular markers,it suggested that Muli citron might be a hybrid origin with citron as male and sour orange(C.aurantium L.)as female parent,similar to the origin of lemon(C.limon(L.)Burm.f).Inerdonato was also from a hybrid origin with citron as the male and C.micrantha Wester as the female parent.In summary,through molecular markers,the genetic relationships of 14 citron genotypes were basically understood,which provided a theoretical basis for exploring the relationships between different citron genotypes and Citron C-05.