ARS | Publication request: Genetic Dissection of Transgressive Flowering Time QTL dth1.1

Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings/Symposium
Publication Acceptance Date: January 15, 2008
Publication Date: March 1, 2008
Citation: Maas, L.F., Ravenscroft, D., Poleczwak, L., McClung, A.M., McCouch, S.R. 2008. Genetic dissection of transgressive flowering time QTL dth1.1. In: Proceedings of the 32nd Rice Technical Working Group Meetings, February 18-21, 2008, San Diego, CA. 2008. CDROM.Proceedings.

Technical Abstract: Transgressive variation in quantitative traits is observed when the descendents of a sexual cross segregate with a range of phenotypes more extreme than that of their parents. The phenomenon of transgressive variation, coupled with selection, drives much of the continued progress achieved through plant breeding. In a previous study, 11 QTLs affecting flowering time were identified in an advanced backcross quantitative trait locus (AB-QTL) study with the wild accession O. rufipogon (IRGC 105491) as the donor parent and the tropical japonica cultivar Jefferson as the elite recurrent parent (Thomson et al. 2003). One of these transgressive loci, days to heading 1.1, (dth1.1), was consistently detected in several studies using interspecific crosses (Thomson et al. 2003; Septiningsih et al., 2003) but not detected in studies using intraspecific crosses (Li et al. 1995; Yamamoto et al. 1998). Within the contiguous sequence across the dth1.1 region, six flowering time candidate genes were identified. Five of these candidate genes had similarity with the protein sequences of Arabidopsis flowering time genes Gigantea (GI), Flowering Locus T (FT) [FTL and FT-L8], and Embryonic Flower 1 (EMF1) and one had similarity to PNZIP, a light regulated leucine (Leu) zipper gene from the Pharbitis nil (Thompson et al. 2006). The objective of the current study is to determine which genes or gene combinations in the dth1.1 region are responsible for the transgressive early flowering phenotype. Segregating NIL families have been used to select lines with individual or combinations of O. rufipogon alleles at the candidate gene loci and to study the contribution of each in the Jefferson background. Preliminary field and control environment data reveal that at least two of the candidate genes must be present in order to reproduce the transgressive flowering phenotype, as lines with a single candidate gene locus have similar flowering as the recurrent parent Jefferson. Expression analysis of all five candidate genes underlying dth1.1, plus heading date genes on chromosome 6, Hd1 and Hd3a, will allow us to establish a model of how these genes interact to determine flowering in rice and provide novel genetic variation for increasing earliness in elite US materials.