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One hundred and sixty-seven rice varieties/laudraces from 23 different rice-growing countries were used for studying the relationship between the amylose content (AC %) and paste viscosity parameters (RVU) through Pearson correlation. AC and paste viscosity parameters were measured using Auto Analyser and Rapid Visco Analysers respectively. Based on all five RVA pasting properties, i.e. peak viscosity (PV), minimum viscosity (MV), breakdown (BD), final viscosity (FV) and setback (SB), the simple paired t-test (at P ¼ 0.05) was carried out to identify varieties that showed non-significant differences (similar) from the check variety, separately for each of the four AC groups, e.g. Waxy rice AC (0-8%, n ¼ 21) -ÔIR29Õ (Philippines); Low AC (8.1-16%, n ¼ 58) -ÔKoshihikariÕ (Japan); Intermediate AC (16.1-24%, n ¼ 64) -ÔLocal SadriÕ (Iran); high AC (>24.1%, n ¼ 24) -ÔKasalathÕ (India). Significant variation among the rice varieties for AC and pasting properties were observed. Means of the AC and the viscosity parameters including PV, MV, BD, FV and SB were 15.8, 416.1, 180.3, 235.8, 380.9 and 200.6 RVU respectively. Significant correlations existed between AC and paste viscosity parameters at AC group level. The paste viscosity parameters, i.e. PV, BD and SB are important within an AC group as far as cooking quality is concerned. In the low AC group, ÔKoshihikariÕ (check) was most preferred by Japanese consumers, which was used for identifying 16 varieties that showed non-significant differences for pasting properties with it. Some of the important Japanese varieties were ÔTodorokiwaseÕ, ÔOwarihatamochiÕ, ÔSasanishikiÕ, ÔReimeiÕ and ÔKinuhikariÕ. These varieties had good cooking quality with low AC, high PV and BD with low SB. In contrast, the Iranian cultivar ÔLocal SadriÕ with good cooking quality had intermediate levels of AC and SB while recording high PV and BD. The varietal diversity for pasting properties available within each AC group may allow the breeder to make effective selections for improving the cooking quality according to consumer choice.

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Tagging of restorer genes for wild abortive (WA) CMS source by studying a 222 individual plants from a F 2 population of a cross between IR58025A £ IR42686R. The restorer line IR42686R that was used in this study had been previously derived through random mating composite population (RMCP) involving 12 parents facilitated by IR36 genetic male sterility. Four Rf genes were tagged to simple sequence repeats (SSR) markers on chromosomes 1, 7, 10, 12 by recessive class analysis. The recombination frequency between a positive marker and Rf locus was calculated using maximum likelihood estimator assuming that all the 46 extremely sterile individual plants were homozygous at the targeted Rf locus. The recombination frequency between the marker and the restorer trait were converted to genetic distances using Kosambi function. A new Rf locus designated as Rf7 on chromosome 12 was found to be linked to RM7003 at a genetic distance of 13.3 cM (LOD 6.12). We report here Wrst, a new molecular marker (RM 6344) linked to Rf4 locus on chromosome 7 that was previously mapped by trisomic analysis. RM443 and RM315 were Xanking the Rf3 gene at a genetic distance of 4.4 (LOD 10.29) and 20.7 cM (LOD 3.98) on chromosome 1, respectively. The Rf6 was Xanked on both side with SSR markers RM258 and RM591 at a genetic distance of 4.4 (LOD 10.29) and 23.3 cM (LOD 3.39) located on chromosome 10. The random mating composite population is an excellent breeding approach to develop superior restorer lines and for pyramiding diVerent Rf genes of diVerent CMS systems. Rf genes tagged with closely linked SSR markers would be facilitating marker assisted selection (MAS) in hybrid rice breeding program by reducing time and workload for identifying potential restorers.

Genetic background effect and environmental sensitivity are two major obstacles for markerassisted breeding (MAB) of complex traits. Background-independent (BI) loci for 1000-grain weight (TGW) and grain shape (GS) were detected over three seasons using a set of reciprocal introgression lines (ILs) from Lemont x Teqing cross with parents having distinctive GS but equal TGW. Reciprocal ILs in advanced (F^^.^g) generations were genotyped using 142 polymorphic simple sequence repeat (SSR) markers on 64 chromosome bins. Nineteen bins of BI loci significantly associated with TGW and/or GS that were identified consistently over multiple seasons and additive effects were in the opposite directions at the same loci between two backgrounds. These 19 bins could be classified into three types: Type I includes four genetic overlapping bins affecting both TGW and GS, Type II includes nine genetic overlapping bins controlling GS component traits, and Type III includes six bins for single GS component. Among them, five stably expressed BI loci (bins 2.2, 2.5, and 3.7 for grain length [GL] and bins 5.2 and 7.4 for grain width [GW]) found consistently over three seasons would be the first choice for MAB. Secondary choice would be the loci that expressed over at least over two seasons and include bins 1.2, 3.3, 4.3 for GL and bins 7.1 and 11.5 for GW. Two related key traits, one for yield (TGW) and the other for grain quality (GS), can now be fully utilized through marker-aided transfer or pyramiding of the identified BI loci in rice iÇiryza sativa L.) improvement programs.

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