No abstract

Seed shattering is an important factor causing loss of grain yield before and during rice harvest. In the present study, the quantitative trait loci regarding shattering scale, breaking tensile strength (BTS) and abscission layer (AL), the parameters evaluating seed shattering habit by hand gripping, a digital force gauge and observation on AL, respectively, were identified by using an doubled haploid line (DHL) population from a cross between a loose-shattering type Tongil variety, 'Samgang', and a moderately difficult shattering japonica variety, 'Nagdong'. Eight QTLs consisted in four QTLs for shattering scale, two QTLs for AL, each one QTL for pulling and bending strength were detected on six chromosomes, respectively. Among them, Qss1 with flanking markers RM6696 and RM476 explained 31% of phenotype variation in shattering scale. Furthermore, two new QTLs controlling shattering habit, Qss5-2 and Qal5-1, were located on chromosome 5 at the interval 5028−5037 and 5021-RM289. They explained 10% and 12% of phenotype variations, respectively. A total of eleven digenic epistatic loci were identified for four parameters. The identification of QTLs affecting seed shattering habits is favorable to thoroughly dissect the genetic mechanism of the shattering habit and to apply for marker-assisted selection in rice breeding system of specific regions.

Anther culturability of rice is a quantitative trait controlled by nuclear‐encoded genes. The identification of quantitative trait loci (QTL) and associated marker selection for anther culturability is important for increasing the efficiency of green plant regeneration from microspores. QTL associated with the capacity for green plant regeneration in anther culture of rice were mapped on chromosomes 3 and 10 using 164 recombinant inbred (RI) lines from a cross between ‘Milyang 23’ and ‘Gihobyeo’. The quantitative trait locus located on chromosome 10 was detected repeatedly when three anther culture methods were applied and was tightly linked to the markers, RG323, RG241 and RZ400. Associations between these markers and the efficacy of green plant regeneration in 43 rice cultivars and two F2 populations, ‘MG RI036’/‘Milyang 23’, and ‘MG RI036’;/‘IR 36’ were analysed. One of these markers, RZ400, was able to identify effectively genotypes with good (> 10.0%) and poor (< 3.0%) regenerability, based on the marker genotypes in the cultivars and two F2 populations. This marker enables the screening of rice germplasm for anther culturability and introgression into elite lines in breeding programmes.

Rice lipid content as one of important ingredients of functional food and industrial products has become an entirely new target in the rice breeding programs worldwide. A genetic linkage map spanning 12 rice chromosomes with an average interval of 10.51 cM between markers was created using 172 DNA markers, which intended to elucidate genetic basis of lipid content in brown rice by QTL detection. Eight QTLs related to lipid content with LOD from 2.52 to 7.86 were mapped on chromosome1, 2, 3, 5, 6, 7 and 9 using a doubled haploid (DH) population from a cross of 'Samgang/Nagdong' with field experiments for five years. Two QTLs of qLC5.1 and qLC6.1 in the intervals 5014-5024 and 6011-RM19696 were repeatedly detected over four years at average LOD scores of 4.85 and 4.21, respectively. Five of eight QTLs tend to increase the lipid content from 'Samgang' alleles. Epistatic and environmental effects played important roles and explained 42.20% of phenotype variations. Three QTLs of qLC6.1, qLC7.1 and qLC9.1 collectively explained much than 27% of phenotype variations and increased 0.25% of lipid content and, showed much than 85% of selection efficiency for the lines with high lipid contents in the F7 population from a cross of 'Samgang/Nagdong'. Thus it provides the sufficient possibility to realize QTLs pyramiding and to promote process of rice breeding.

During brown planthopper (BPH) feeding on rice plants, we employed a modified representational difference analysis (RDA) method to detect rare transcripts among those differentially expressed in SNBC61, a BPH resistant near-isogenic line (NIL) carrying the Bph1 resistance gene. This identified 3 RDA clones: OsBphi237, OsBphi252 and OsBphi262. DNA gel-blot analysis revealed that the loci of the RDA clones in SNBC61 corresponded to the alleles of the BPH resistant donor Samgangbyeo. Expression analysis indicated that the RDA genes were up-regulated in SNBC61 during BPH feeding. Interestingly, analysis of 64 SNBC NILs, derived from backcrosses of Samgangbyeo with a BPH susceptible Nagdongbyeo, using a cleaved amplified polymorphic sequence (CAPS) marker indicated that OsBphi252, which encodes a putative lipoxygenase (LOX), co-segregates with BPH resistance. Our results suggest that OsBphi252 is tightly linked to Bph1, and may be useful in marker-assisted selection (MAS) for resistance to BPH.