Important Genomic Regions Mapping; Transfer Patterns To Derivatives And Effects Analyses In Rice Core Parent Guichao 2

Guichao 2, one of the most important rice core parents in China, has given rise to over thirty elite cultivars, and the total cultivation area of Guichao 2 and its derivatives amount to 14.66 million hectares since 1983. Thus, analyzing and recognizing Guichao 2 on a genomic level will definitely benefit the breeding practice, especially for core parents and for the promotion of hybrid combinations in the future.In the present study, Simple Sequence Repeat marker (SSR) based genome-wide screening and important agronomic characters investigation were performed, and combined with QTLs/gene analysis to learning the genetic structure, the effects of core genomic regions of Guichao 2 and its transfer patterns to its derivatives, and the main results were details as followed:1. Genetic diversity of Guichao 2 and its parents, derivatives was investigated with 425 pairs of polymorphic SSR markers. A total of 1095 alleles were detected among 16 cultivals, and the number of alleles each primer pair ranged between 2-7 with an average of 2.58. The polymorphic information content (PIC) value ranged from 0.12 to 0.83 and averaged 0.38. Genetic similarity (GS) among the 16 cultivars varied from 0.72 to 0.93 with an average of 0.81, indicating that the genetic diversity is not abundant. Guichao 2 and its parents, derivatives could be clustered into two groups with UPGMA cluster analysis based on SSR analysis, and the resuls are according with their pedigrees relationships.2. Origins map of Guichao 2's genetic regions was drawn based on genome-wide screening.371 polymorphic makers constitute 383 genetice regions,42 of them have single origin, and others have multiple origins.42 genetic regions cover chromosome physical distance 24659.154kb,6.63% of whole genome size. For the 42 single origin regions, Chaoyangzaol8 and Guichao 2 contribute more genetic components to Guichao 2 than other parents, and their genetic contribution ratio were 2.00% and 1.46%, respectively. The 42 single origin genetic regions inherited from a given parent or characteristic by Guichao 2, and be thought of important genetic regions of Guichao 2. There were 37 QTLs/gene mapped on these important genetic regions, most of them associated with yield factors, and some of them are related to plant type morphogenesis and resistance to diseases. For example, Glna, a main QTL associated with filled seeds per panicle, which can explain 44% of variation. A drawft gene, d2 mapped on important genetic regions too, and both of them had been cloned successifully. Moreover, some QTLs/gene related to yield factors, espcically associated with thousand grains weight, mapped on the genetic regions characteristic of Guichao 2, and these genetic regions uniquled by Guichao 2 might inherited from the parents dose not be involved in this study.3.3. Results of deliver rules of yield factors and quality traits from Guichao 2 to its derivatives indicates that:thousand grains weight, effective panicle number, tillers number and plant height decrease, while seed setting ratio, filled seeds per panicle and plant weight are increased; as for quality characters, head rice ratio, chalky ratio, chalk size, apparent amylase content and protein content decline, while grain length, length-width ratio, transparency and gel consistency rise, and gelatinization temperature is constant. Otherwise, chalky ratio, chalk size, grain length, length-width ratio and transparency of Guichao 2 are similer to Chaoyangzao 18's, indicating these characters might be inherited from Chaoyangzao 18. Furthermore, some yield factors, seed setting ratio, filled seeds per panicle, tillers number and plant weight for instance, gelatinization temperature and protein content inherits by derivatives from Guichao 2, while most of quality characters of Guichao 2's, such as head rice ratio, chalky ratio, chalk size, rain length, length-width ratio, transparency, gel consistency and apparent amylase content are sifted out in breeding programs due to hardly reach high quality standards.4. Markers developed from starch-synthesis genes were using to test genotype of Guichao 2 and its parents Chaoyangzao 18,Guiyangai 49 and its derivatives. Only 114/113, developed from Pul (gene encoding pullulanase), amplified polymorphic bands among ten cultivars, Chaoyangzao 18-. Qingliuai and Fengqingai are classied into Nipponbare genotype, others are classied into Indica genotype. Other markers did not amplified polymorphism among the ten cultivars, which are grouped into Indica genotype.5 A total of 348 polymorphic markers and 833 polymorphic alleles were detected. In addition,78 genomic regions of Guichao 2 are identified inherited by these derivatives, their contribution ratios ranging from 14.29% to 85.71%, with an average of 41.25%. Moreover,61 genes and quantitative trait loci (QTLs) were found to be located on these genomic regions,35 of them are associated with yield factors, and others mainly involve in stress response, growth and development, resistance to diseases and plant type.