Genetic Analysis Of The Leaf Traits And Resistance To Citrus Canker Disease In Citron And Its Hybrids

Citrus is the world’s largest fruit.But,citrus bacterial canker disease is difficult to control and cannot be eradicated.In addition,the citrus products in the epidemic area of ulcers have been restricted by the markets of all pest-free areas at home and abroad,seriously affecting the development of citrus industry.Due to this reason,many researchers at home and abroad have conducted lots of research on the prevention and treatment of citrus canker disease.Almost all citrus resources have been shown to be susceptible,and the disease-resistant breeding may be the only way to fundamentally treat citrus canker disease.Through years of screening,our laboratory has selected a unique resistant Xanthomonas citri subsp.citri named citron C-05 from a large number of citrus resources which provide genetic resources and practical guidance for disease-resistant breeding.Based on this,a systematic resistant disease evaluation and genetic diversity analysis were performed on the citron germplasm.Then,through the hybrids between susceptible mono-embryonic‘Shatian’pumelo and citron C-05,a total of 848 hybrids were obtained,explore the genetic trend and correlation of the leaf morphological characters and genetic regularity of resistant citrus bacterial canker disease.The foundation for the exploration of the disease resistance mechanism and resistant gene has been laid.The experimental results are as follows:(1)Eleven citron germplasms were evaluated for their anti-canker disease by relative resistance index and comprehensive disease index.The germplasm was divided into four grades,and the citron Yuan and citron Aiguo are similar to citron C-05 which performed cell death was found.(2)The 14 SRAP primer combinations were used to detect the DNA polymorphism of14 citron resources.70 PCR bands and 33 are polymorphism bands were amplified by the 14primer combinations,and the ratio of polymorphism bands for primer combination is47.14%.The 14 SRAP primer can distinguish all 14 citron germplasms.In addition,when the genetic distance 0.43 was used as the critical value,the citron germplasm could be divided into 7 groups,and the citron C-05 was not clustered with other germplasm.(3)In the hybrids of‘Shatian’pumelo and citron C-05,the traits of leaf tip index,petiole length,leaf shape index,petiole wing width and young leaf color had some genetic trends and correlations,and both were normal distribution,which may be a quantitative characters for multi-gene control;The young leaf color characteristics can be used as morphological markers to those which similar to hybrids between‘Shatian’pumelo and citron C-05 identified(4)Analysis of the genetic regularity of resistance to citrus canker in the hybrids between‘Shatian’pumelo and citron C-05,and the 848 hybrids were divided into 4disease-resistant grades,there were 206 high susceptible and 438 susceptible,134 resistance,and 70 high resistant plants.High susceptible and susceptible were classified as susceptible,and high resistance,resistant plants were classified as resistance.Finally,through the x~2analysis showed that the ratio of susceptible and disease-resistant plants met the separation ratio of 3:1.Therefore,The disease resistance traits of hybrids are controlled by two pairs of genes.