Detection Of Leifsonia Xyli Subsp. Xyli In Introduced Cultivars Of Fruit Cane And Genetic And Physiological Differences From Donors And Their Irradiation Lines Using Co⁶⁰

Fruit Cane is a sort of chewing cane, due to the less cultivar, much seedling disease and leading to serious variety degradation. For asexual reproduction crops, irradiation breeding using Co⁶⁰-gamma ray has the advantages of genetic variation stability and high breeding efficiency etc. Therefore, following researchs will be carried out in this study.?1?To provide the basis for fruit cane virus-free seedling production, Leifsonia xyli subsp.xyli will be detected andtheir DNA sequences will be analyzed in six introduced cultivars of fruit cane.?2? To provide theoretical basis for fruit cane radiation breeding, genetic variation of donors and their irradiation lines will be studied using ISSR and SCo T molecular markers based on different genotypes of fruit cane irradiated by Co⁶⁰ gamma-ray.?3? To provide materials for breeding high yield, good quality and stronge resistance fruitcane clutivars, main protective enzymes, enzyme that related to sucrose synthesis and soluble osmotic substances will be detected and compared between fruitcane donors and their irradiation lines to select some irradiation lines with physiological indexes of up regulation. The main resaech results were as follows:?1? PCR and nested-PCR was used to detect Leifsonia xyli subsp.xyli?Lxx?, the causal bacterium of sugarcane stunting disease?RSD?, for seven cultivars of fruit cane, including Qianzhe 08-1497, Qiantang No.5, Yunnan hongpi, Guangdong huangpi, Qianzhe08-688, Qiantang No.3 and Badila. The nucleotide sequences from the second round amplified products of nested-PCR in fruitcane cultivars of Guangdong huangpi, Yunnan hongpi, Qiantang No 3 and Badila?isolates number followed Lxx-Gd-gz1, Lxx-Gd-gz2, Lxx-Gd-gz3 and Lxx-Gd-gz4? were determined and analyzed. The results showed that detection rate of RSD bacteria was 20%?1/5? only in Qianzhe 08-688 and Lxx detection rate was 0% in the remaining six fruit cane cultivars by using PCR detection. However, Lxx detection rate was 0% only in Qianzhe 08-1497, detection rate of Lxx was 75% in Qiantang No.5 and Guangdong huangpi, detection rate was 100% in Yunnan hongpi, Qianzhe 08-688, Qiantang No. 3 and Badila using nested-PCR detection. The intergenic transcribed spacer?ITS? regions of 16s-23 s r DNA of isolates Lxx-Gd-gz1, Lxx-Gd-gz2, Lxx-Gd-gz3 and Lxx-Gd-gz4 shares almost 100% nucleotide identity each other and shares almost 99% nucleotide identity with isolates from Brazil, Australia, USA?Luisanna? and China?Yunnan province, Fujian province and Zhanjiang city, Guangdong province?. It was indicated that the genetic stability of Lxx was extremely high, and the variation was minimal.?2? Eleven SCo T polymorphic primers and 13 ISSR polymorphic primers were screened from 40 SCo T primers and 50 ISSR primers, respectively. A total of 101 bands were amplified by SCo T using 11 polymorphic primers, of which, 82 bands were polymorphic, the polymorphism was 81.19%, the average single primer amplified bands number was 9.18, the average number of alleles Na was 1.8119, the average effective number of alleles?Ne? was 1.4948, the average gene diversity index H was 0.2912, the average Shannon's information index?I? was 0.4348. A total of 103 bands were amplified using 13 screened ISSR polymorphic primers, of which, 82 bands were polymorphic bands, the average polymorphic rate was 79.61%, the average number of amplified bands were 7.92 by single primer, the average number of alleles Na was 1.7961, the average effective alleles?Ne? was 1.5839, the average gene diversity index H was 0.3240, the average Shannon's information index?I? was 0.4702. These polymorphic parameters showed that SCo T and ISSR markers were suitable for further application in genetic diversity research in fruit cane. According to the unweighted pair group method arithmetic averages?UPGMA? clustering analysis based on SCo T, ISSR and SCo T+ISSR data sets, different degree of genetic variation was produced between three cultivars of fruitcane, including Badila, Qingpi fruit cane and Guizhou fruit cane, and their irradiation lines irradiated by Co⁶⁰ gamma-ray using dose of 50 gy with 30 min. At the same time, the genetic basis of Badila was close to Qingpi fruit cane, farther to Guizhou fruit cane was also confirmed.?3? Physiological indexes of irradiation lines derived from three fruitcane cultivars were randomly up or down in the department of seedling, tillering and jointing stage according to comparison of main protective enzymes, enzyme that related to sucrose synthesis and soluble osmotic substances. For example, Badila irradiation line No.1, Qingpi irradiation line No. 2, Qingpi irradiation line No. 5 and Guizhou irradiation line No. 4 and 5 were up in some physiological indexes. It will provide materials to further breed high quality and stronge resistance fruit cane cultivar.