Pleiotropism of the Photoperiod-Insensitive Allele of Hd1 on Heading Date, Plant Height and Yield Traits in Rice

Abstract

Five populations segregated in isogenic backgrounds and three sets of near isogenic lines (NILs) overlapping in a 362.3-kb region covering heading date gene Hd1 were developed from the indica rice cross Zhenshan97 (ZS97)/Milyang 46 (MY46). They were used to analyze the effects of Hd1 on heading date, plant height and yield traits. In a background of the parental mixtures, the photoperiod-sensitive allele derived from ZS97 functioned in promoting and delaying flowering in the natural short-day and long-day conditions, respectively. In the background of ZS97, no response to the photoperiod was observed, whereas the photoperiod-insensitive allele derived from MY46 functioned in delaying flowering, increasing plant height, and enhancing grain productivity. The additive effects estimated in two NIL sets were 6.14 and 6.14 d for heading date, 4.46 and 5.55 cm for plant height, 10.82 and 11.54 for the number of spikelets per panicle, 6.82 and 8.00 for the number of grains per panicle, and 2.16 and 2.23 g for grain yield per plant, which explained 94.1% and 96.3%, 70.5% and 84.8%, 52.4% and 55.2%, 28.9% and 39.2%, and 36.5% and 26.9% of the phenotypic variances, respectively. Since the photoperiod-insensitive allele of Hd1 confers a long vegetative phase, it is a good candidate for breeding rice varieties with high yielding potential for low latitudes.

Effects ofHd2in the presence of the photoperiod-insensitive functional allele ofHd1in rice

“…1). This population has been used to construct NILs for analyzing the effects of Hd1 (Zhang et al, 2012). It was found that the functional Hd1 ZS97 allele was insensitive to photoperiod in the genetic background of ZS97 but promoted heading by 4.64−6.14 days under NSD and NLD conditions.…”

“…Zhenshan 97 (ZS97) is an early-season rice variety carrying the functional PS allele Se-1 u at the Hd1 locus but has been shown to be photoperiod insensitive (Wei et al, 2012). As compared with Milyang 46 (MY46) carrying photoperiod-insensitive allele Se-1 e , the ZS97 allele promotes heading under both natural short-day (NSD) and natural long-day (NLD) conditions, and meanwhile decreases plant height, spikelet number, grain number and grain yield (Zhang et al, 2012). …”

Overexpression of OsMYB1R1–VP64 fusion protein increases grain yield in rice by delaying flowering time

“…In this study, we found that overexpression of OsMYB1R1-VP64 increased grain yield and plant height in rice by delaying flowering time (Figs 1 and 2). Several rice flowering-related pleiotropic genes such as Hd1, Ghd7, DTH8, and DTH7 were discovered in the last 10 years [4,6,7,9]. These genes delay flowering, increase plant height, and increase grain number.…”

“…Many pleiotropic genes that function in delayed flowering along with higher yield have been investigated. Those genes have been described as Days to heading 7 (DTH7), Early heading date 2 (Ehd2), Heading date 1 (Hd1), Grain number, plant height and heading date 7 (Ghd7), and Days to heading 8 (DTH8) [4,[6][7][8][9]. Under natural long-day (NLD) conditions, Ghd7 delays flowering by about 20 days and causes yield increases of 50%, and both Hd1 and DTH8 delay flowering time with increasing grain number per spike.…”

Functional Characterization of Genes/QTLs for Increasing Rice Yield Potential

“…Increased expression level of Hd3a and RFT1 reduces number of primary branches per panicle in the line combining Hd1 and Ehd1 [65,66]. In addition, Hd1 increases number of spikelets per panicle and grain yield by suppressing Hd3a expression and delaying heading date [67].…”