| The common cultivated potato (Solanum tuberosum L.) is a tetraploid with tetrasomic inheritance and high heterogeneous genetic base, genetic segregation is more complicated than ones with disomic inheritance. The genetic analysis and improvement of characters, such as tuber processing quality traits and yield components which tend to be quantitatively inherited, are far more difficult than those at diploid potato. Reviewing the earlier studies indicated that a few systematic investigations on genetics of important traits in potato were untaken and most focused on estimates of combing ability for agronomic traits due to limited materials and methodologies available. So it is necessary to exploit existing genetic variation and to dissect agronomic and processing quality traits at diploid level as the diploid potatoes represent an advantage which can simplify the genetic analysis by using diploid genetic model. This method enables a more efficient exploitation of genes of desired characters from 2x species and integration of these genes into tetraploid cultivated potatoes by using of chromosome manipulation and genetic engineering.In the present study, analysis of general combing ability (GCA) and specific combing ablity (SCA), genetic main effects and geneticxenvironment interaction effects, heritability for chipping quality and yield components, and genetic correlations between traits was conducted, using a genetic model, based on 2 year experimental data of quantitative traits of 6 progeny populations from 4 diploid parents in a mating design of Griffing's method IV. A genetic informative segregation population propagated from hybrids of two diploid parents with significant differences in processing qualities and agronomic traits was used to develop molecular genetic linkage maps by AFLP and SSR technologies. Furthermore, quantitative trait loci (QTL) analysis of chipping qualities and yield components was performed. The main conclusions are as follows:1. The significant positive effects of GCA and additive for yield components, and the significant negative effects of GCA, additive and dominance for chipping color were found in the parent of 11379-03. The high significant positive effects of GCA and additive for tuber yield were showed in the parent of CH72.03. And the parent of 08675-21 was with significant negative effects of GCA and additive for tuber chipping color. It was suggested that 11379-03 and CH72.03 be good parents for tuber yield improvement, 11379-03 be also used for chipping color improvement, while 08675-21 be an excellent parent for chipping color but with low tuber yield. Positive effects of SCA and dominance for tuber yield were significant with CH72.03×11379-03, and 08675-21×10875-04 showed significant negative effect of dominance for chipping color.2. The estimated results of genetic effects and heritability for chipping qualities and important agronomic characters indicated that:Performance of tuber dry matter content was controlled by additive minor poly-genes because of the high significant additive effect and relatively low narrow sense heritability (42.5%).Effects of additive and additive x environment interaction, and gene interaction (dominance effect) were of high significant importance for chipping color and tuber set. Additive heritability of chipping color (60.7%) was the highest amongst traits studied, that makes it possible to screen this trait at early breeding generations. Additive heritability of tuber set was 47.1%.Tuber size was with the lowest additive heritability (25.2%) among characters studied in the experiments, while variation of tuber size was affected by effects of additive, gene interaction and dominancexenvironment interaction as well.Effects of additive and gene interaction (dominance) were significant for tuber yield, and the additive effect, with 53.5% heritability, was more important.3. There were strong positive additive genetic correlation between tuber dry matter content and each of chipping color, tuber yield and tuber set. Chipping color was positively associated with tuber yield and tuber size. Tuber yield showed very strong positive additive and dominance genetic correlations with tuber set and tuber weight.4. Based on AFLP and SSR markers, a molecular linkage map of potato was initially developed by using F1 segregating population from the cross between the diploid potato parents of 08675-21 and 09901-01. 152 AFLP and 6 SSR markers were organized into 17 main linkage groups covering a total distance of 946cM. The average interval distance was 5.99 cM between markers. Length of linkage groups varied from 29.0 cM to 89.0 cM and the number of markers linkage to each group ranged from 5 to 22. Using 3 SSR markers, the linkage groups of 12, 14 and 17 were located to chromosome 4, 2 and 9, respectively.5. In the segregating population (02018) derived from 08621-75 x 09901-01, the character of chipping color presented a normal distribution but inclined to one side. It could be concluded that chipping color was a quantitative trait controlled by major genes. Through evaluation in three years, 12 diploid genotypes of 02018-32, 02018-44 and 02018-93 etc. were screened out with light chipping color immediate after harvesting and with desirable agronomic traits. The results of cold chipping experiments showed that the reconditioning of chipping color was easier for the genotypes stored under 6°C for 80 days than those stored under 4℃for 90 days. 6 diploid genotypes of 02018-93, 02018-94, 02018-105, 02018-176, 02018-77 and 02018-248 were identified as good cold chippers through two years experiments being carried out under 4℃/6℃cold-storage and reconditioning at 18℃.6. Interval mapping and multiple-QTL model mapping (MQM) methods were employed in mapping and analyzing of QTL-controlled traits of chipping color, tuber dry matter content, tuber set and tuber size. 39 putative QTL, of which were 19 for chipping color including 3 major gene loci, 13 were for tuber dry matter content including 3 major gene loci, and 7 were for tuber set, were mapped on 10 LGs of the population 02018. None QTLs were determined for tuber size. Accordingly the genetic contributions to traits for each QTL were also estimated.
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