Genetical Analysis And QTL Mapping For Plant Height Related Traits In Rice (Oryza Sativa L.)

Genetical analysis and molecular mapping for beneficial genes in rice are among major topics in rice genetic and breeding researches. In the present study, two new semidwarf genes were found from Chinese landrace, Qian-nong (QN) and Te-ai (TA), respectively. The ralationship between semidwarf or dwarf gene and resistance to bakanae disease was analyzed, quantitive traits loci(QTL) mapping for resistance to bakanae disease, heading synchrous and plant height uniformity were carried out using the doubled haploid (DH) population.1. Genetical analysis of dwarfism in two local varieties. Results indicated that the dwarfism in QN and TA were controlled by two recesive dwarf genes, respectively, one of which was allelelic to sd-1 and the other was non-allelic to sd-1. Two lines XQA (Xin-qian-ai) and XTA (Xin-te-ai) possessing new semi-dwarf genes sd-q(t) and sd-e(t) were isolated respectively from QN and TA.2. Allelism test between sd-q(t) and other genes conferring dwarfism or semi-dwarfism indicated that sd-q(t) was non-allelic to d-29, d-32, d-59, sd-g, sd-6 and d-1.3. The response to gebberellic acid (GA₃) and PP₃₃₃ of rice varieties/lines carrying different dwarf genes and gene combinations were studied at seedling stage. Among the dwarf genes tested, the new semi-dwarf gene sd-q(t) was insensitive to GA3, whereas most of the others were sensitive. The order of sensitivity to GA3 from the higher to the lower ranked as: d-c(t), D-53, sd-1 (indica), i-sd-1, sd-1 and sd-e(t) combination (TA), d-29, multi-gene combination, d-1, Sd-1 (tall plant), sd-6, d-32, sd-g, sd-q(t) and sd-1 and sd-q(t) combination (QN). And in PP333 tested, sd-q(t), sd-g and eui are the most sensitivity, and multi-gene combination variety 83N1041 and DM107-4 with d-59 are the most insensitivity. The results suggested that use GA3 or PP333 was useful for screening some dwarf genes un-allelic to sd-1 at seedling stage are effective.4. Agronomic traits such as fertility, grain weight and grain number per panicle were investigated by useing NILs conducted from different dwarf genes with ZX5T as back-crossed parent. NILs with d-32, sd-g, sd-6 and sd-q(t) semi-dwarf gene had better agronomic traits, suggesting that those genes would be utilized in rice breeding to replacement the sd-1 gene.5. A total of 32 rice genotypes carrying different dwarf or semi-dwarf genes were inoculated with the fungus Fusarium moniliforme, Sheldon or treated with 50mg/L GA₃ in order to select resistant resources to rice bakanae disease from the dwarfism materials. The elongated length of the seedlings was measured, and the death percentage of the seedlings after transplanted to field was also counted. Results indicated that significant correlation between elongated length of the seedling treated by GA3 and bakanae fungus was found. Rice materials carrying dwarf gene such as sd-1 were not only sensitivity to GA3 but also susceptive to rice bakanae disease. However, materials carrying dwarf gene d-1 were insensitive to GA3 but susceptive to bakanae. All materials carrying d-29, sd-6 or sd-q(t) genes showed resistant to bakanae. The present study indicated that dwarf and semi-dwarf rice materials might be useful resources for improvement of bakanae resistance in rice breeding programs.6. A japonica/indica doubled haploid (DH) population ,derived from Chunjiang06 and TN1, was used to analyze QTL for resistance to rice bakanae disease by artificial inoculation at the budding stage. Both of the parents were susceptible to bakanae disease. Two QTL (qB1 and qB10) were detected on chromosome 1 and 10, respectively, and both of the two QTL showed additive effects.7.Simultaneous heading of plants within the same rice variety, termed as heading synchrony (HS), is an important factor affecting simultaneous ripening of the variety. Uniformity in the height of main stem and tillers is a key factor affecting ideal plant type, contributing to the super high-yield rice breeding. Understanding the genetic basis of the heading synchrony and plant height uniformity (PHU) may contribute to breeding good plant type varieties with simultaneous heading and ripening. In the present study, a japonica/indica doubled haploid (DH) population, derived from a cross between Chunjiang 06 (a good HS variety) and TN1 (a poor HS variety) was used to analyze quantitative trait locus (QTL) for HS, panicle height uniformity (PHU) and other related traits, such as early heading date (EHD), heading date (HD),late heading date (LHD) and panicle number per plant (PN). A total of ten QTL for the five traits distributed on 7 rice chromosomes were detected. One QTL, qHs8, was detected for HS, which explained 27.7% of the total genotypic variance. The qHs8 allele from CJ06 could reduce the heading difference by 3.3 days. Three QTL, qPhu4, qPhu10 and qPhu12 were detected for PHU, which explained 41.9% of the total genotypic variance. Two QTL for EHD located in the chromosomes 8 and 9, shared similar regions for the two QTL for HD and LHD. Two QTL for panicles number (PN) located on the chromosome 4 and 5, explained 34.2% of the total variations. Results of this study may be useful for marker assisted breeding for the improvement of the heading synchrony and panicle layer uniformity.