Abstract
Appropriate flowering time is crucial for successful grain production, which relies on not only the action of individual heading date genes, but also the gene-by-gene interactions. In this study, influences of interaction between Hd1 and Ghd7 on flowering time and yield traits were analyzed using near isogenic lines derived from a cross between indica rice cultivars ZS97 and MY46. In the non-functional ghd7ZS97 background, the functional Hd1ZS97 allele promoted flowering under both the natural short-day (NSD) conditions and natural long-day (NLD) conditions. In the functional Ghd7MY46 background, Hd1ZS97 remained to promote flowering under NSD conditions, but repressed flowering under NLD conditions. For Ghd7, the functional Ghd7MY46 allele repressed flowering under both conditions, which was enhanced in the functional Hd1ZS97 background under NLD conditions. With delayed flowering, spikelet number and grain weight increased under both conditions, but spikelet fertility and panicle number fluctuated. Rice lines carrying non-functional hd1MY46 and functional Ghd7MY46 alleles had the highest grain yield under both conditions. These results indicate that longer growth duration for a larger use of available temperature and light does not always result in higher grain production. An optimum heading date gene combination needs to be carefully selected for maximizing grain yield in rice.
Highlights
Flowering time is a pivotal factor in the adaption of cereals to various ecogeographic environments and agricultural practices, which is controlled by an intricate genetic network
Effects of Hd1 and Ghd7 on heading date (HD) were investigated using three populations derived from the rice cross Zhenshan 97 (ZS97)/Milyang 46 (MY46)//MY46///MY46
The R1-near isogenic lines (NILs) population was tested under both the natural short-day (NSD) and natural long-day (NLD) conditions, and the R2-F2 and R2-NIL populations were tested in NLD conditions only
Summary
Flowering time is a pivotal factor in the adaption of cereals to various ecogeographic environments and agricultural practices, which is controlled by an intricate genetic network. Florigens are at the core of the network, which are encoded by Hd3a and RFT1 in rice [1,2]. The expression of Hd3a and RFT1 are regulated by two important pathways mediating by Hd1 and Ehd, respectively [3]. The function conversion of Hd1 is related to PhyB, Se5, Ghd and Ghd8 [4,5,6,7,8]. Function loss of any of these genes attenuates the conversion and maintains Hd1 as an activator under any day-length conditions. Ehd activates florigen genes expressions to promote flowering under both the SD and LD conditions [9]. Ehd likely acts as a signal integrator, and its expression is regulated by many genes [3]. Recent studies revealed that Hd1 represses expression of Ehd through interaction with Ghd or DTH8 [6,7,8]
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