Initial flowering date (IFD) is closely related to mature period of peanut pods.  In present study, a population of recombinant inbred lines (RIL) derived from the cross between Silihong (female parent) and Jinonghei 3 (male parent) was used to map QTLs associated with IFD.  The RIL population and its two parental cultivars were planted in two locations of Hebei Province, China from 2015 to 2018 (eight environments).  Based on a high-density genetic linkage map (including 2 996 SNP and 330 SSR markers) previously constructed in our laboratory, QTLs were analyzed using phenotypic data and the best linear unbiased prediction (BLUP) value of initial flowering date by inclusive composite interval mapping (ICIM) method.  Interaction effects between every two QTLs and between individual QTL and environment were also analyzed.  In cultivated peanut, IFD was affected by genotypic factor and environments simultaneously, and its broad sense heritability (h2) was estimated as 86.8%.  Using the IFD phenotypic data from the eight environments, a total of 19 QTLs for IFD were detected, and the phenotypic variation explained (PVE) by each QTL ranged from 1.15 to 21.82%.  Especially, five of them were also detected by the BLUP value of IFD.  In addition, 12 additive QTLs and 35 pairs of epistatic QTLs (62 loci involved) were identified by the joint analysis of IFD across eight environments.  Three QTLs (qIFDB04.1, qIFDB07.1 and qIFDB08.1) located on chromosome B04, B07 and B08 were identified as main-effect QTL for IFD, which had the most potential to be used in peanut breeding.  This study would be helpful for the early-maturity and adaptability breeding in cultivated peanut.

 

Heading date is a crucial agronomic trait.  However, rice usually delays heading due to the photoperiod, temperature, hormones or age.  The present research was conducted to analyze the mechanism controlling heading date in F₁ hybrid rice.  We constructed two test-crossing populations using two introgression lines (ILs), P20 and P21 coming from SH527/FH838 as the male parent, respectively, and male sterile line Jin23A as the female parent.  Meanwhile, the F₁ hybrids of H20, obtained by mating P20 with Jin23A and having no heading, and H21, from the crossing between P21 and Jin23A having normal heading, were both observed under long days.  Here, we analyzed the photoperiodic response of F₁ hybrids by transcriptome and metabolome profiling.  The greater differences displayed in the transcriptome and the metabolome were caused by photoperiod (exogenous) instead of genes (endogenous).  The coping mechanism resulted from long days (LD) in H20, leading to differences in the circadian rhythm and glutathione metabolism relative to other samples.  The circadian oscillator and GSH/GSSG cycle typically regulate ROS homeostasis, and both of them are responsible for modulating ROS in H20 under LD condition.  Both circadian rhythm genes and the reported genes related to heading date function via the DHD1/OsMFT1-Ehd1-RFT1-OsMADS14/OsMADS18 pathway and the glutathione metabolism pathway by regulating oxidative reduction processes.  Both pathways are involved in the heading process and they interacted through the oxidative reduction process which was induced by photoperiod regulation, and all of them collectively modulated the heading process.  The results of this study will be helpful for unraveling the mechanism of F₁ hybrid responses to unheading under LD condition.