| 1.QTL mapping of grain shape and grain weight in riceGrain weight is an important determinant of grain yield in rice,and grain shape determines grain weight.In order to explore new QTL for grain shape and grain weight in rice,a Geng/japonica(GJ)breeding population was used to identify QTL for grain shape related traits.The main results are as follows:1.1 The F2 and F3 populations both consisting of 200 lines were developed from a cross between a salt-tolerant material D123 as the male parent and a dominant genic sterile line with the background of Huang-huai GJ background as the female parent.120 polymorphic molecular markers were screened from the parent D123 and a mixed pool of F2 lines,and were used to perform genotyping of each F2 line.A genetic linkage map with a genetic length of 1639.5 c M was constructed,which covered all 12 chromosomes.1.2 QTL mapping of grain shape and grain weight was conducted using the composite interval mapping(CIM)method,with a combination of the constructed genetic linkage map and phenotypic data of F2 and F3 generations.A total of 35 QTL were detected in F2 and F3 populations.Nine QTL for grain length were detected,which were distributed on chromosome 1,2,5,6,8 and 12 respectively.Among those,q GL2 and q GL8 were repeatedly detected in two populations.The increasing allele of q GL2 was derived from the dominant genic male sterile material,which explained 14.34% and 12.35% of the phenotypic variation in the two populations,respectively.The increasing allele of q GL8 came from the salt-tolerant parent D123,which explained 12.09% and 21.88% of the phenotypic variation in the two populations respectively.q GL1 was only detected in the F3 population,and the increasing allele came from the parent D123,explaining 21.28% of the phenotypic variation.Nine QTL for grain width were detected,which were distributed on chromosome 1,4,5,6,8 and 11 respectively.Among those,q GW1 and q GW4 were repeatedly detected in two populations.The increasing allele of q GW1 came from the parent D123,which explained10.85% and 5.37% of the phenotypic variation in the two populations respectively.The increasing allele of q GW4 came from the dominant genic male sterile material,which explained6.43% and 9.33% of the phenotypic variation in the two populations respectively.q GW6-1 and q GW6-2 were only detected in the F3 population,and both the increasing alleles were from D123,which explaining 13.32% and 15.53% of the phenotypic variation respectively.Ten QTL for grain width were detected,which were distributed on chromosome 2,4,5,6and 8 respectively.Among those,q LWR2 and q LWR5 were repeatedly detected in two populations.The increasing allele of q LWR2 came from the dominant genic male sterile material,which explained 11.8% and 10.42% of the phenotypic variation in the two populations respectively.The increasing allele of q LWR5 came from the parents D123,which explained7.75% and 4.18% of the phenotypic variation in the two populations respectively.q LWR4-1 was only detected in the F2 population,which explaining 23.61% of the phenotypic variation.Seven QTL for grain weight were detected,which were distributed on chromosomes 1,2,4and 8 respectively.Among those,q TW1-2 and q TW2 were repeatedly detected in two populations.The increasing allele of q TW1-2 came from the parents D123,which explained33.82% and 34.28% of the phenotypic variation in the two populations respectively,and was confirmed as the cloned gene GL1 by sequencing.The increasing allele of q TW2 came from the dominant genic male sterile material,which explained 8.45% and 4.09% phenotypic variation respectively.The detected QTL in this study could provide valuable genetic resources for the basic research of rice grain shape and grain weight and the genetic improvement of rice yield and quality.2.Development of salt tolerance markers in riceImproving the salt tolerance of rice with salt-tolerant genes is helpful to popularize rice planting in saline-alkali land.In order to promote the improvement of salt tolerance of rice varieties,molecular markers for four salt-tolerance related genes with natural variation,namely Os HAK21 and Os PAO3 controlling salt-tolerance germination,and SKC1 and Os ARF18 controlling salt tolerance at seedling stage,were developed,and then were used to evaluate the genotypes of rice germplasm and varieties preserved in our group.The main results are as follows:2.1 Haplotype analysis of the four salt-tolerant genes were analyzed,based on the gene full-length sequences of 38 rice germplasm materials with high-quality reference genomes and the sequences of elite allele reported by predecessors.Five main haplotypes of gene Os HAK21 were classified,and the elite haplotype Hap A was carried by GJ rice varieties represented by Nipponbare.Five main haplotypes of Os PAO3 gene were classified,and the elite haplotype Hap C was carried by some xian/indica(XI)rice varieties represented by 9311.Four main haplotypes of SKC1 gene were classified,and the elite haplotype Hap D was carried by some XI rice varieties represented by Zhenshan 97.Three main haplotypes of gene Os ARF18 were classified,and the elite haplotype Hap A was carried by GJ rice varieties represented by Nipponbare.2.2 Molecular markers consisting of In Del,CAPS or d CAPS were developed respectively for the elite haplotype of each salt-tolerant gene,according to the information of specific variations.The CAPS marker HAK21 IN2 was developed for gene Os HAK21 based on the T/C variation at site +1251 of the second intron,and the coupled restriction enzyme was Dra I.The d CAPS marker PAO3 E9 was developed for gene Os PAO3 based on the A/G variation at site+3474 of exon 9,and the coupled restriction enzyme was Eco R I.The d CAPS marker SKC1 5U was developed for gene SKC1 based on the A/G variation at site-1250 of the 5’UTR,and the coupled restriction enzyme was Eco R I.The In Del marker ARF18 5U was developed for gene Os ARF18 based on the 514 bp In Del at site-2858 of the 5’UTR.Genotyping of 19 selected representative germplasm materials were conducted using these four markers,and the results were satisfactory.2.3 Haplotypes of salt-tolerant genes were analyzed in 76 germplasm resources from different countries and 70 GJ rice varieties approved by northern provinces of China,using the four markers.Results showed that the elite haplotypes of Os ARF18 and Os HAK21 were mainly distributed in GJ rice,while those of SKC1 and Os PAO3 were mainly distributed in XI rice.The salt-tolerant markers developed in this study and the germplasm materials with evaluated salt-tolerant genotypes can provide valuable molecular markers and donor materials for improving salt tolerance of rice. |
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