Evaluation Of The Resistance To Citrus Canker Disease Of Lemon And Its Self-crossed Seedlings

Citrus canker disease has the disadvantages of being difficult to control and cannot be eradicated,which seriously affects the development of the citrus industry.Breeding and using resistant varieties may be the only way to fundamentally treat citrus canker.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 has cell necrosis occurs after inoculation of citrus canker,which is a typical HR response,indicating that citron C-05 has an immune response to citrus canker disease in the ETI layer,and there is a resistance gene.Lemon is the hybrid of citron and is the main high-acid citrus variety.In order to explore whether the lemon has acquired the resistance gene of citrus canker in the process of genetic evolution,in this study,systematic evaluation of citrus canker disease was performed on different lemon varieties.A self-crossing group of 459 strains was established for the lemon variety ’Eureka’,which has the largest cultivated area.The zygotic embryos in the self-crossing progeny were found,and the self-crossing progeny were identified by in vitro injection to identify the resistant citrus canker,which provided resources for the disease-resistant breeding of citrus canker,and laid a theoretical foundation for the subsequent mining of disease resistance genes.The experimental results are as follows:(1)11 lemon varieties were evaluated for anti-citrus canker disease by injecting in vivo.It was found that the ’Continella’,’D’Amalfi’,’Femmninello SR’ had a defensive reaction during the invasion of citrus cankers,and the other types of lemons compared with the ’Continella’ and ’Sorrento’ More resistant to citrus canker disease.According to the disease index analysis,it is found that ’Sorrento’ is a more susceptible grade;the comprehensive disease index of ’Chaparro’,’Fior d’arancio’ and ’Interdonato’ is higher than that of the extremely susceptible variety ’Bingtang Orange’.(2)Eight pairs of SSR primers were identified by SSR molecular markers to identify the self-crossing progeny of ’ Eureka’ lemon,and 76 zygotic embryo progeny were identified from 459 self-crossing progeny.(3)Analysis of leaf morphological differences between zygote embryo seedlings and nucleus embryo seedlings revealed that leaf shape index,leaf tip index,wing length,wing width and petiole length could not be used to distinguish ’ Eureka ’ lemon.The zygotic embryo and the nucleus embryonic morphological markers.The variation of the leaf length of the ’ Eureka ’ lemon zygotic embryo seedlings was greater than that of the bead embryo seedlings,but no directional variation occurred.(4)433 strains of ’Eureka’ lemon self-crossing progeny were identified for in vitro susceptibility to citrus canker disease,including 13 resistant plants,357 susceptible plants,and 63 susceptible plants,the ratio was 1:46.Comparing the unidentified self-crossing progeny with the traits of the zygotic embryo seedlings,it was found that the ratio of the zygotic embryo seedlings to citrus canker was 1:10,the type of susceptible plants is significantly more than that of unidentified self-crossing progeny and the pearl embryo seriously affected the ’ Eureka ’ lemon to the citrus canker.The genetic law of disease resistance is analyzed,and zygotic embryos may still exist in unidentified self-crossing progeny.