155 Australian Journal of Crop Science    3(3):155-166 (2009)  ISSN: 1835-2707 Genetic dissection of biomass production, harvest index and panicle characteristics in indica-indica crosses of Iranian rice (Oryza sativa L.) cultivars *Hossein Sabouri 1 , Atefeh Sabouri 2 , Ahmad Reza Dadras 3 1 Department of Plant Production, Gonbad High Education Center, P.O. Box 163 Golestan, Gonbad, Iran 2 Department of Agronomy and Plant Breeding, Faculty of Agriculture, University of Guilan, P.O. Box 41635-1314, Rasht, Iran 3 Former student in Azad University of Lahijan *Corresponding author: Saboriho@yahoo.com Abstract Improvement of rice (Oryza sativa L.) yield through breeding requires a good understanding of genetic factors that control component traits. In the current study, traits associated with this multiplicative relationship were investigated in a field trial with F 2 and F 2:3 population of rice. One-hundred-and-ninety-two individuals and families derived from a cross between two genetically divergent high-yielding varieties, Khazar (KHZ, indica type with a large biomass) and Tarommahalli (TAM, indica type with a low biomass), were grown in Rice Research Institute of Iran and Gonbad High Education Center to detect QTLs for biomass and related traits. Result of mapping on F 2 population showed that QTLs controlling GWP (qGWP-3a and qGWP-3b) overlapped with the QTLs for number of SNP (qSNP-3a and qSNP-3b) and the QTL for HI (qHI-3). Five QTLs were mapped for harvest index. These QTLs were showed the large effects on the harvest index and explained 21.35 to 31.28% of the total phenotypic variance. Result of F 2:3 population showed that QTLs controlling GWP (qGWP-2, qGWP-7 and qGWP-12) overlapped with the QTLs for number of SNP (qSNP-2, qSNP-7 and qSNP-12). Clustering of the QTLs for different traits at the same markers interval in both of mapping population was observed for GWP, HI and SNP. These result implied that HI, might partly share a common genetic basis with GWP and SNP. Our result indicated that breeding methods of QTLs pyramiding by using marker-assisted selection could be very useful for the development of new varieties with a high level of grain yield. Keywords: biomass; grain yield; rice (Oryza sativa L.); QTL mapping. Abbreviation: KHZ_ Khazar variety; TAM_ Tarommahalli variety; PH_ plant height; HI_ Harvest index; GWP_ weight of grain panicle; SNP_ spikelet number of panicle; LFL_ length of flag leaf; WFL_ width of flag leaf; BI_ biomass; QTL_ Quantitative trait loci; CIM_ composite interval mapping Introduction Rice (Oryza sativa L.) is the world’s second most important cereal crop that providing half of the feed for world population and more than 90 percent of rice produced is consumed in Asia. Therefore, it is necessary to increase rice production (Yoshida, 1981). Most of the earlier studies have been used potential classic plant breeding method to improve traits contributing to yield (Brondani et al., 2002). Yield, yield components and agronomically useful traits for example rice grain number, grain weight, plant height, biomass and harvest index have continuous phenotypic distributions, implying that many genes with relatively minor effects, termed quantitative traits loci (QTLs) control them (Falconer