| In recent years, with the continuous expansion of squash cultivating, virus disease became more serious especially in the year of high temperature and drought, which causing enormous losses in yield and quality. The typical symptom is fold and blistering, even distortion, lopsided ill-leaf , shorting plant, there are motley with light green and deep green, and some of the motley are yellowed. Among the strains, CMV is the most predominant. CMV is transmitted in a non-persistent manner by over 60 aphid species. Attempts to control vector with insecticides have been unsuccessful. The development of virus-resistant varieties is likely to be the most effective, environmentally friendly and sustainable approach to control virus disease. It is important to identify resistance genes effective against the virus, to obtain information on their mode of inheritance and to incorporate these into improved cultivars. Molecular markers are considered to be one of the most useful tools to assist in the selection of strain-specific. The study was carried out using a F2 population from a cross between resistant inbred line and susceptible inbred line. Bulked segregant analysis (BSA) was applied to identify RAPD markers linked to the resistance to CMV. The main results are as follows: 1. The morphological characters of the viruses were observed by electron microscotnv(EM),The types of virus in our samples is CMV by identified with ELISA. 2. The resistance to CMV were studied by field natural identification . Segregation ratio obtained was 1:3,χ2=0.0176 and less than χ20 05(df=I) =3.84.This indicates that the resistance to CMV is controlled by a major gene as well as a recessive gene . 3. The optimum reaction system of RAPD in squash was studied in order to ensure stability and reproducibility of RAPD . After testing some important influencing factors of RAPD in squash ,the results showed that in 25ul RAPD reaction system the optimum concentration were 3 mmol/L MgCl2, 0.2 mmol/L dNTPs, Taq DNA polymerase 1.0U ,primer 15 ng/μl ,template DNA 10 ng/μl .The PCR amplification procedure used in this study was as follow : pre-denature at 94℃for 5 min, then 94℃30s,37℃30s 72℃90s,for 40 cycles, finally extended at 72℃for 5 min. 4. K01, K02 and F2 population of K01×K02 containing 76 individual plants were used for molecular mapping of the resistance gene by bulked segregant analysis. 520 random primers and 310 double primers with arbitrary sequences were chosen for RAPD amplication .It was found that the polymorphism between the R-bulk and S-bulk could be detected by 6% and 5% of the primers as well as two RAPD markers S439 and S19+S345 were linked to the resistance gene of k01 with the overcross value of 7.5% and 11.8%,genetic distance of 7.1 cM and 11.7 cM.
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