THREE MAJOR GENES, INCLUDING SE-1, FROM NATURALLY OCCURRING VARIANTS CONTROLS A CRITICAL PHOTOPERIODIC RESPONSE OF FLOWERING IN RICE (ORYZA SATIVA)

Authors: GU, XING-YOU - NDSU; CHEN, ZONG-XIANG - YANGZHOU UNIVERSITY,CHINA; Foley, Michael

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/18/2004
Publication Date: 8/19/2004
Citation: Gu, X-Y., Chen, Z., Foley, M.E. 2004. Three major genes, including Se-1, from naturally occurring variants controls a critical photoperiodic response of flowering in rice (Oryza sativa). [Abstract]. Plant Genomics in China V. Page No. 60.

Interpretive Summary: Differentiation in the photoperiodic response of flowering has been key to the evolution and wide geographic distribution of Asian cultivated rice. Rice is an essentially short-day plant, although all temperate and an overwhelming majority of tropical varieties exhibit only quantitative flowering responses to daylengths in excess of a critical period. We screened rice crosses in which the hybrid F1s flower later than the late-flowering parents and identified hybrid genotypes that cannot flower under a daylength of 14 h. Genetic analysis revealed that a set of three genes assembled from both parents were responsible for the critical response by complementation and quantitatively regulated flowering responses by other epistases. One of these genes is allelic to the locus Se-1, which is 1.7 cM away from the RFLP marker RG64 in the mapping population. Wild-type alleles at the three loci have been introduced into the genetic background of a day-neutral breeding line by seven generations of backcrossing and phenotypic identification under the 14 h daylength. Segregation patterns for the critical and quantitative responses in the seven generations confirmed the trigenic model, suggesting that these genes act in a linear manner to repress transition from the vegetative to reproductive phases under long daylengths. This set of genes also provides a model to understand the genetic mechanism underlying hybrid vigour, which is usually an obstacle to the use of heterosis, and the selection for early maturation in rice breeding.

Technical Abstract: Differentiation in the photoperiodic response of flowering has been key to the evolution and wide geographic distribution of Asian cultivated rice. Rice is an essentially short-day plant, although all temperate and an overwhelming majority of tropical varieties exhibit only quantitative flowering responses to daylengths in excess of a critical period. We screened rice crosses in which the hybrid F1s flower later than the late-flowering parents and identified hybrid genotypes that cannot flower under a daylength of 14 h. Genetic analysis revealed that a set of three genes assembled from both parents were responsible for the critical response by complementation and quantitatively regulated flowering responses by other epistases. One of these genes is allelic to the locus Se-1, which is 1.7 cM away from the RFLP marker RG64 in the mapping population. Wild-type alleles at the three loci have been introduced into the genetic background of a day-neutral breeding line by seven generations of backcrossing and phenotypic identification under the 14 h daylength. Segregation patterns for the critical and quantitative responses in the seven generations confirmed the trigenic model, suggesting that these genes act in a linear manner to repress transition from the vegetative to reproductive phases under long daylengths. This set of genes also provides a model to understand the genetic mechanism underlying hybrid vigour, which is usually an obstacle to the use of heterosis, and the selection for early maturation in rice breeding.