Abstract
Although flowering in rice has been extensively investigated, few studies focused on genetic interactions. Flowering evaluation of two recombinant inbred line (RIL) populations involving photo-insensitive rice cultivars, Bengal and Cypress, and a weedy rice accession, PSRR-1, under natural long-day (LD) conditions, revealed six to ten quantitative trait loci (QTLs) and a major QTL interaction. In addition to the validation of several previously cloned genes using an introgression lines (IL) population of PSRR-1, a few novel QTLs were also discovered. Analysis of the marker profiles of the advanced backcross lines revealed that Hd1 allele of PSRR-1 was responsible for the photoperiodic response in the near-isogenic lines (NILs) developed in both cultivar backgrounds. Based on the phenotypic and genotypic data of the NILs, and NIL mapping population and the transcript abundance of key flowering pathway genes, we conclude that Hd1 and its interaction with a novel gene other than Ghd7 play an important role in controlling flowering under LD conditions. Our study demonstrates the important role of genetic interaction that regulates flowering time in rice and the need for further investigation to exploit it for breeding adaptable rice varieties.
Highlights
Flowering time is a complex agronomic trait governed by both genetic factors and environmental cues[1,2]
The current study focused on the elucidation of the genetic interaction involved in the flowering transition in response to photoperiod using unique genetic materials such as recombinant inbred line (RIL) and introgression line (IL) populations, and near-isogenic lines (NILs) developed from crosses involving two photo-insensitive cultivars and a weedy rice accession
We used both RIL34 and IL35 populations developed from crosses involving cultivated and weedy rice, which allowed assessment of the magnitude of the QTL effects on phenotype as well as discovery of a genetic interaction
Summary
Flowering time is a complex agronomic trait governed by both genetic factors and environmental cues[1,2]. Ghd[7] is an important member of the flowering pathway that regulates plant height, heading date, and grain number[16]. It delays flowering under LD by repressing Ehd[1] transcription. Since the time of transition from the vegetative to flowering stage is vitally important for maximizing productivity, elucidation of the new genetic determinants and their interactions controlling this transition is essential to breed new high yielding rice varieties adapted to a specific cropping season or agroclimatic region. We further demonstrated that early flowering and photo-insensitivity in weedy rice was due to genetic interaction between Hd1 and a novel gene other than Ghd[7] on chromosome 7
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