Comparative efficiency of pedigree, modified bulk and single seed descent breeding methods of selection for developing high-yielding lines in rice (Oryza sativa L.) under aerobic condition

The knowledge about the relative efficiency of the different breeding methods may greatly help the plant breeder in selecting abetter method to be adopted in a particular crop. In the present experiment, the comparative efficiency of three selectionmethods, viz., pedigree, modified bulk and single seed descent (SSD) were assessed in F3, F4, F5 and F6 generations of a crosscombination Moroberekan/IR20 of rice. Bulk population showed superiority over pedigree for grain yield, panicle length, numberof panicles, number of tillers and harvest index in F3 generation. Pedigree method was found to be superior over bulk and SSDfor grain yield per plant in F4 and F5 generations. In the three breeding methods, mean values of grain yield showed directionalshift across the generations. In F6 generation, the pedigree-derived lines showed higher superiority over mean value than linesderived from SSD and modified bulk for grain yield, number of panicles and harvest index. No significant differences existedbetween pedigree and modified bulk-derived F6 lines for grain yield and harvest index. Inter-generation correlation coefficientswere significant and positive between all the generations for grain yield, number of tillers and number of panicles. Significantand positive correlations were observed between these three characters across generations supporting the intergenerationcorrelation results. Visual selection based on the number of tillers and number of panicles per plant was very effective forincreasing yield in bulk and pedigree methods

Identification of QTL for growth- and grain yield-related traits in rice across nine locations of Asia

Rice double-haploid (DH) lines of an indica and japonica cross were grown at nine different locations across four countries in Asia. Genotype-by-environment (G x E) interaction analysis for 11 growth- and grain yield-related traits in nine locations was estimated by AMMI analysis. Maximum G x E interaction was exhibited for fertility percentage number of spikelets and grain yield. Plant height was least affected by environment, and the AMMI model explained a total of 76.2% of the interaction effect. Mean environment was computed by averaging the nine environments and subsequently analyzed with other environments to map quantitative trait loci (QTL). QTL controlling the 11 traits were detected by interval analysis using MAPMAKER/QTL. A threshold LOD of > or = 3.20 was used to identify significant QTL. A total of 126 QTL were identified for the 11 traits across nine locations. Thirty-four QTL common in more than one environment were identified on ten chromosomes. A maximum of 44 QTL were detected for panicle length, and the maximum number of common QTL were detected for days to heading detected. A single locus for plant height (RZ730-RG810) had QTL common in all ten environments, confirming AMMI results that QTL for plant height were affected the least by environment, indicating the stability of the trait. Two QTL were detected for grain yield and 19 for thousand-grain weight in all DH lines. The number of QTL per trait per location ranged from zero to four. Clustering of the QTL for different traits at the same marker intervals was observed for plant height, panicle number, panicle length and spikelet number suggesting that pleiotropism and or tight linkage of different traits could be the possible reason for the congruence of several QTL. The many QTL detected by the same marker interval across environments indicate that QTL for most traits are stable and not essentially affected by environmental factors. (Résumé d'auteur

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