Dissertation > Agricultural Sciences > Plant Protection > Pest and Disease Control > Horticultural Crops Pest and Disease Control > Vegetable pests > Melons, pests and diseases > Cucumber pests and diseases

Study on Inheritance and Molecular Markers of Resistance to the Root-Knot Nematode (Meloidogyne incognita) in Cucumber Introgression Lines

Author ZhangYanXia
Tutor ChenJinFeng
School Nanjing Agricultural College
Course Olericulture
Keywords cucumber introgression line southern root-knot nematode(Meloidogyne incognita) inheritance SSR molecular marker
CLC S436.421
Type Master's thesis
Year 2011
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The root-knot nematode is a serious pest, found all over the world, and can causes sever yield losses in many significant economic crops. According to investigation, root-knot nematode can cause yield losses of forty crops from the world above 100 billion dollars approximately, over 20 percent about vegetable, peanut, tobacco and fruit tree. In 1885, root-knot nematode was found firstly in cucumber root by Britainic Scientist Berkeley, at present it is reported to have 90 different species. Root-knot nematode can cause yield reduce 11 percent in 24 vegetables. Cucumber is one of the most susceptible vegetables, then root-knot nematodes(Meloidogyne incognita) is the major pathogeny for cucumber. Resistant breeding is the most basic and effective method to resolve the problem, for there are no efficient measures to prevent and control the disease by now. The resource of resistant germplasm and genetic analysis of resistance are the precondition and base, the work of collecting and screening the resistance resource has been carried on at the home and abroad. In this study, we obtain a resistant material of interspecific cucumber introgression line by screening, the parents and F2 populations were analyzed inheritance to Meloidogyne incognita, which derived from resistant parent’10-1’and susceptible parent ’beijingjietou’, utilizing SSR markers, marker-assisted selection was performed in F2 population of 10-1 x beijingjietou. The results are as follows:1. Tests for resistance to Meloidogyne incognita of 14 cucumber introgression lines were carried out at seedling stage through artificial inoculation. The results revealed that there were no immune materials to Meloidogyne incognita, and two accessions were moderate resistance, by purification of 10-1, we obtain two resistant materials,10299F-4 and 10299F-5, The disease index was 2.0 respectively.2. By analyzing phonotype data of F2 population originated from resistant parent 10-1 and susceptible parent’beijingjietou’ after inoculating, we found among 139 F2 individuals, the resistant plants account for 109, meanwhile, the number of susceptible plants is 30. Though X2 test X20.05,1=0.69<X20.05=3.84. consistent with the 3R:1S ratio of separation, it is proved that the resistance to Meloidogyne incognita in cucumber introgression line10-1 is dominant and controlled by one major gene.3. Nine SSR primers were found to linkage to Meloidogyne incognita resistance gene likely by screening between two parents and resistant and susceptible pools, these nine SSR primers are validated using F2 individuals. The results showed that only two SSR primers are linked to resistant gene, utilizing mapmarker3.0 to analyze data, we found that the genetic distance with Meloidogyne incognita resistance gene was 23.2cM and 28.8cM.4. Two SSR primers which linked to resistant gene were amplified among resistant parent, susceptible parent and Cucumis hystrix Chakr. The special band which is about 150bp appeared in resistant parent and Cucumis hystrix Chakr, but this band was not amplified in susceptible parent. These two bands were recycled and cloned,sequences of the two fragments were determined by blast analyses, the results showed that these two sequences had high homology with Cucumis hystrix Chakr., a band amplified from SSR13237 showed high sequence identity(89.33%) with band originated from Cucumis hystrix Chakr., the other band from SSR23265 exhibited extremely high sequence identity(95.57%), this results indicated that resistant parent 10-1 is originated from interspecific hybridization, and we speculateed that the fragments from wild sour cucumber may be relative to resistance to southern root-knot nematode.

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