FINE-SCALE GENETIC AND PHYSICAL MAPPING OF A RICE PHOTOPERIOD SENSITIVITY GENE, HD3

¹ Institute of the Society for Techno-innovation of Agriculture, Forestry and Fisheries, Tsukuba, Ibaraki 305-0854, Japan

² National Institute of Agrobiological Resources, Tsukuba, Ibaraki 305-8602, Japan

³ Bio-oriented Technology Research Advancement Institution, Omiya, Saitama 331-8537, Japan

Eleven quantitative trait loci (QTLs) controlling heading date in rice were identified based on analysis of a population derived from a cross between japonica cultivar Nipponbare and indica cultivar Kasalath. In a previous study, QTL Hd3, which was identified as a photoperiod sensitivity gene, was located between restriction fragment-length polymorphism (RFLP) markers R1952 and C1032 on chromosome 6. To narrow the genomic region of Hd3, we used linkage analysis with 792 segregants and RFLP markers located around Hd3. Progeny testing was performed under short-day conditions on segregants in which recombination occurred around Hd3. As a result, we constructed a fine-scale genetic map of the Hd3 region. We screened a Kasalath genomic cosmid library and a Nipponbare genomic P1-derived artificial chromosome (PAC) library to construct a physical map of the Hd3 region. Cosmid contigs do not yet cover the whole of this region. Linkage analysis using expressed sequence tags and cosmid end clones as RFLP markers enabled us to narrow the target region. We isolated 4 PAC clones in this region, 2 of which covered Hd3. Sequencing analysis of the selected PAC clone and screening of the Kasalath genomic cosmid library are in progress to identify the positional candidate gene for Hd3.