| Cross breeding was still main methods for breeding new apple cultivars. Genetic evaluation of main characters can provide basic genetic theory for selecting parents and improving efficiency of apple breeding. Molecular marker as a newly appeared technique can enrich the results of normal methods,and supply molecular basics for breeding program. WRKY transcription factors play important roles in plant defense signaling network. Alternaria leaf spot is considered one of the most important limiting factors with apple growth and yield in Weibei loess plateau. Clone and identification a gene related to apple Alternaria f. Mail resistance can provide application in apple genetic engineering. The experiment carried out the evaluation of parental breeding values with Fuji and PinkLady, the genetic variation and selection of fruit traits in apple hybrids by applying of mathematical and statistical methods, the molecular markers on fruit acid / low acid trait by SSR, the comprehensive evaluation and the function of MdWRKY gene with resistance to apple Alternaria f. Mail. The main results were as follows:1. Analysis on the fruit traits of parents and hybrid progenys. The genetic variation of fruit traits were analyzed in 216 hybrids of Fuji×PinkLady. The results showed that Fuji and PinkLady had differences in the fruit traits. The inheritance of fruit skin color was simple qualitative heredity and the red color showed quantitative heredity which was controlled by multi genes. The inheritance trends of fruit shape appeared distinct central variation. The fruit size,SSC and TSC tended to be less than parental mean, which causing the fruit quality of progenies was poor. The hybrids showed coarser flesh, firmer texture, less juice and smaller core size.2. Study on comprehensive selection of fruit traits in apple progenys. Based on the several year average traits and expected breeding goals of Fuji and PinkLady, the selective standards of each trait were drawn up. A set of twelve traits for selection such as single weight, fruit shape, firmness and so on, were formulated as the suitability indicators of hybrids. A five-graded method was adopted to quantitatively evaluate each indicator of hybrid and hierarchic analysis as well as adopted to determine weight of each index. A set of indices as well as quantitative model for evaluating the fruit traits of hybrids were developed. At the same time, according to the improved contingency table method, a model of comprehensive selection of apple traits for high yield was also proposed. The practice proved that two model was useful for apple breeding.3. SSR markers linked to the Ma gene for fruit acidity in apple. A molecular marker linked to the acid gene (Ma) in apple was explored based on the 216 progenies of Fuji×PinkLady by BSA and SSR technique. A total of 102 primers were screened and SSR markers (CH03d12-104+ CH03d12-118) closely linked to Ma gene was identified, and the linking distance of two markers respectively is 3.24cM and 2.31cM. The SSR marker analysis showed that the fruit acid trait was governed by one major gene and one additive gene. Ma was completely dominant to ma. The CH03d12-104 + CH03d12-118 marker was further confirmed in 40 apple varieties which showed concordant rate between the genotype and the phenotype were 97.5%.Simultaneously the potential application of two markers in a marker-assisted quality breeding programme is further discussed.4. Comprehensive evaluation and forecast on physiological indices of Alternaira alternata f. sp. mali (AaM) resistance in F1 hybrids of apple.Based on F1 hybrids of Fuji and PinkLady, the physiological indices of resistance to AaM were comprehensively evaluated and predicted, which were used to value the F1 hybrids'single capacity of AaM resistance to some new independent comprehensive indexes by principal component analysis. The comprehensive value of different F1 hybrids AaM resistance was obtained by using subor-dinative function,So the AaM resistance of different F1 hybrids can be evaluated. Meanwhile, the regression were analyzed between the comprehensive value of AaM resistance and the value of single index to AaM resistance.The results showed that the comprehensive value were higher, the F1 hybrids AaM resistance were better. The net photosynthetic rate, chlorogenic acid content,phenylalanine ammoniumlyase content in apple leaves and thickness of hundred leaves would be used as indexes of evaluating AaM resistance in apple. The analyzed regression indicated the function's square were prominent.The results of Cluster analysis show that strength of the order was the same. The regression predicted Apple hybrids individual resistance.5. Function of MdWRKY gene with resistance to apple Alternaira leaf spot. One MdWRKY was isolated from Qinguan apple, which is resistant to Alternaria leaf spotusing RT-PCR approaches. MdWRKY was 1224bp and encoded a 331 amino-acid protein. Its GenBank accession number is HM859901. The MdWRKY protein was targeted to the nucleus and activated the expression of a reporter gene, consistent with the functioning of a transcription factor. When plants were infected with the pathogen Alternaria alternata f. sp. mali, MdWRKY wasinduced dramatically. Similarly, treatment with hormones SA and MeJA increased transcription significantly. Overexpression in tobacco also enhanced resistance to Phytophthora parasitica var. nicotianae Tucker. These results suggest that MdWRKY is a positive regulator of the defense response in higher plants. |
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