Abstract
BackgroundRice (Oryza sativa L.) is a staple food crop worldwide. Its yield and quality are affected by its tillering pattern and spikelet development. Although many genes involved in the vegetative and reproductive development of rice have been characterized in previous studies, the genetic mechanisms that control axillary tillering, spikelet development, and panicle exsertion remain incompletely understood.ResultsHere, we characterized a novel rice recombinant inbred line (RIL), panicle exsertion defect and aberrant spikelet (pds). It was derived from a cross between two indica varieties, S142 and 430. Intriguingly, no abnormal phenotypes were observed in the parents of pds. This RIL exhibited sheathed panicles at heading stage. Still, a small number of tillers in pds plants were fully exserted from the flag leaves. Elongated sterile lemmas and rudimentary glumes (occurred occasionally) were observed in the spikelets of the exserted panicles and were transformed into palea/lemma-like structures. Furthermore, more interestingly, tillers occasionally grew from the axils of the elongated rudimentary glumes. Via genetic linkage analysis, we found that the abnormal phenotype of pds manifesting as genetic incompatibility or hybrid weakness was caused by genetic interaction between a recessive locus, pds1, which was derived from S142 and mapped to chromosome 8, and a locus pds2, which not yet mapped from 430. We fine-mapped pds1 to an approximately 55-kb interval delimited by the markers pds-4 and 8 M3.51. Six RGAP-annotated ORFs were included in this genomic region. qPCR analysis revealed that Loc_Os080595 might be the target of pds1 locus, and G1 gene might be involved in the genetic mechanism underlying the pds phenotype.ConclusionsIn this study, histological and genetic analyses revealed that the pyramided pds loci resulted in genetic incompatibility or hybrid weakness in rice might be caused by a genetic interaction between pds loci derived from different rice varieties. Further isolation of pds1 and its interactor pds2, would provide new insight into the molecular regulation of grass inflorescence development and exsertion, and the evolution history of the extant rice.
Highlights
Rice (Oryza sativa L.) is a staple food crop worldwide
In this study, histological and genetic analyses revealed that the pyramided pds loci resulted in genetic incompatibility or hybrid weakness in rice might be caused by a genetic interaction between pds loci derived from different rice varieties
The identification of recombinant inbred line (RIL) pds with abnormal phenotypes RIL pds was observed in an F2:3 family derived from a cross between two indica rice cultivars, 430 and S142 with normal plant architecture and normal panicle development
Summary
Rice (Oryza sativa L.) is a staple food crop worldwide. Its yield and quality are affected by its tillering pattern and spikelet development. At the transition from the vegetative to the reproductive phase of plant growth, the shoot apical meristem (SAM) acquires inflorescence meristem (IM) identity and initiates lateral branch or flower development. The AMs initiated in the leaf axils develop into tillers on the main culms, whereas the axillary primordium produced by the IM gives rise to ten or more primary branches. The IM degenerates, leaving a degenerated point at the base of the uppermost lateral branch of the rice inflorescence, or panicle (Additional file 1: Figure S1A, D) [1]. The few meristems at the base of the primary branch acquire secondary branch meristem identity and develop into secondary panicle branches, while the other AMs grow into lateral spikelets. Following the maturation of reproductive organs (stage In8), the uppermost internode of the tiller rapidly elongate and the inflorescence protrudes from the sheath of flag leaf [3]
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