| Watermelon (Citrullus lanatus) is an important fruit vegetable. China is the biggest watermelon producer of area and output in the world. While the large-scale production makes the continuous cropping obstacle of watermelon is becoming more prominent, which eventually leads to the Fusarium wilt and other soil-borne diseases been much severe. The watermelon Fusarium wilt belongs to Fusarium oxysporum f.sp. niveum which could infects the vascular system, been the most serious disease of watermelon production in the world, and has become a major obstacle restricting watermelon production. New watermelon varieties with fine quality and disease resistant are urgently needed in watermelon industry. Therefore, breeding new varieties of high-quality and disease resistant is very important practically On the basis of extensive collection and evaluation of germplasm resources with resistance to Fusarium wilt, by means of molecular markers and genetic analysis to resistant gene,3 innovation watermelon cultivers which highly resistant to Fusarium wilt and 2 new varieties with high quality and resistance to Fusarium wilt were breeded.The results are as follows:1. Seven diploid watermelon cultivars with different levels of resistance to Fusarium wilt were selected to make combinations and analysis the resistant inheritance using Griffing’s diallel crossing system Ⅱ. The results showed that the resistant inheritance of diploid watermelon to fusarium wilt was controlled by dormant polygene and conformed to the additive-dominance model and the former effect was more important than the latter. The susceptibility was partially dominant to resistance. The dominant gene showed the effect of increasing susceptibility; while the dormant gene showed the effect of decreasing susceptibility. Numbers of dormant genes were more than that of the dominant genes in all the parents. The resistant inheritance of watermelon to fusarium wilts differred in cross combinations made from different watermelon material. The resistance to fusarium wilt race 1 was inherited dominantly by single gene existing gene interaction in all cross combinations of high resistant varieties of Calhoun Gray and Sugarlee.Fifty one tetraploid watermelon gemplasm resources were inoculated with Fusarium wilt in seeglling stage, which only 2 moderate resistant materals were getton.The combinations of 3 tetraploid and 4 diploid watermelon cultivers were made with incomplete diallel mating method (NCⅡ). The inoculated evaluation of resistant to Fusarium wilt and variance analysis results of combining ability to parents and tetraploid F1 hybrids indicated that the resistance of tetraploid F1 hybrids was controlled by additive and non-additive heredity components and the former was more important relatively than the later. The additive heredity component of tetraploid female parent was more important than that of diploid male parent.2. The concentration of Mg2+, dNTPs, and primer in RAPD and ISSR systems for watermelon genomic DNA assay was optimized.’Sumi No.5’was used as an analyzed sample. The screened optimization system of RAPD for watermelon genomic DNA was 20μL, which contained primer 0.4 μmol·L-1, dNTPs 200 μmol·L-1, Mg2+ 2.0 mmol·L-1, DNA 20ng, 1×buffer, Taq E 1.0U. The optimization system of ISSR was 16μL, which contained primer 0.25 μmol·L-1, dNTPs 160 μmol·L-1, Mg2+ 1.0 mmol·L-1, DNA 20ng, 1 ×buffer, Taq E 0.64U.The above optimized RAPD and ISSR systems were applied to analysis the polymorphism of watermelon mapping parents of 2 high resistant to Fusarium wilt F1 hybrids which parents have greet difference both in area and origin. The results of mapping parents’64-1(?)-3’(female parent of’Sumi No.5’, from U.S.A) and’6(?)-2’(male parent of’Sumi No.5’, from Taiwan, China) showed that the RAPD primers polymorphism rate was 14.67%; ISSR primers polymorphism rate of ISSR analyses was 12.23%. In mapping parents’23(?)-1’(female parent of’Kangbingsumi’, from China) and’4-1(?)-2’(male parent of’Kangbingsumi’, from U.S.A), the RAPD primers polymorphism rate was 16.77%. These showed that the genetic background of watermelon mapping parents tested was narrow although the parents of 2 F1 hybrids have greet difference both in area and origin.Genetic diversity of 35 watermelon resistant germplasms was inoculated and evaluated with Fusarium wilt and analyzed by using SRAP molecular marker technique. The results shown that the polymorphic rate is 58.88%. The average numbers of amplified band for each primer is 9.67. Moreover, the cluster analysis results of the 35 cultivars using NTSYS software showed that cultivars from the same place in the same resistance grade clustered together. Cluster analysis of different disease resistant of watermelon materials using SRAP markers at DNA level could not only reflect the genetic relationship of these materials, but also the resistant genetic relationship and their origin.3. Buy using Calhoun Gray as a resistant material,3 yellow flesh and small fruit type watermelon lines with high resistant to Fusarium wilt was selected by using crossing, backcross, successively self-pollination and disease resistant screening. The innovation watermelon line’R-2-1-2’harbors high general combining ability in fruit sugar content, high resistant ability to Fusarium wilt race 1 which controlled by a single dominant gene.By using inoculation with Fusarium wilt and molecular marker techniques,2 new watermelon varieties of’Zaokangjingxin’ and ’Sumi No.5’with fine quality and high resistant to Fusarium wilt were breeded, which have evaluated and proved by the Committee of crop varieities approval of Jiangsu provence in 2004 and 2005 respectively and released 133000 hm2.’Zaokangjingxin’ has granted variety rights of plant (Jiali-CNA20040616.7)4. The esterase, peroxidease and polyphenoloxidase and seed protein of Watermelon hybrids’Sumi No.5’,’Zaokangjingxin’,’Kangbingsumi’and their parents at the stage of dry seeds, sprouting and 5 days seedlings germinated were studied by gradient-PAGE. The results showed that there was an obvious band of POD that could effectively distinguish hybrids from its parents in 5 days seedlings germinated of’Zaokangjinxin’.Two molecular marker systems, RAPD (Random Amplified Polymorphic DNA) and ISSR (Inter-Simple Sequence Repeat), which based on polymerase chain reaction, were used to evaluate genetic purity of 2 watermelon hybrids’Kangbingsumi’ and ’Sumi No.5’,which highly resistant to Fusarium wilt. Genomic DNA from the F1 hybrids and their corresponding parental lines was analyzed with RAPD primers and ISSR primers. In ’Kangbingsumi’,3 female parent-specific markers,4 male parent-specific markers, and 2 male and female parent-specific markers simultaneously were selected respectively, which can be applied successfully for testing the genetic purity of this hybrid. In’Sumi No.5’,4 RAPD female parent-specific bands,1 male parent-specific band were selected. There were only 2 ISSR female parent-specific bands useful to test the hybrid’Sumi No.5’purity. We found that ether one female parent-specific primer or one male parent-specific primer or one codominant primer could be an efficient implement for testing the genetic purity of hybrid seeds. |
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