Ppd-1Remodels Spike Architecture by Regulating Floral Development in wheat

Abstract

The determination of spike architecture is critical to grain yield in wheat (Triticum aestivum), yet the underlying mechanisms remain largely unknown. Here, we measured 51 traits associated with spike architecture and floral development in 197 wheat accessions with photoperiod sensitive and insensitive alleles. We included five distinct allele combinations at the Photoperiod-1 (Ppd-1) loci. A systematic dissection of all recorded phenotypes revealed connections between floral development, spike architecture and grain yield. Modifying the durations of spikelet primordia initiation did not necessarily affect spikelet number. In addition, Ppd-1 loci clearly influenced rachis dry weight, pointing to the rachis vascular system as a potential target for higher yield. Ppd-1 displayed opposite effects on the durations of pre and post-anthesis phases. Ppd-1 controlled carpel size, but not anther size. Finally, the photoperiod-insensitive alleles of Ppd-1 triggered floral degeneration. In parallel, we profiled the spike transcriptome at six stages and four positions in three Ppd-1 genotypes which consists of 234 samples. Integrating phenotypic and expression data suggested that loss of function in Ppd-1 loci delayed floral degeneration by regulating autophagy and extended floret development by regulating genes in different families. Therefore, we concluded that Ppd-1 remodels spike architecture by regulating floral development in wheat. Appleyard, 1987). During WA stage, the meristematic dome initiates 7-9 floret primordia within each individual spikelet (1-3 primordia fewer than the maximum number) (Kirby and Appleyard, 1987). The lemmas of florets 1 and 2 at the base of the spikelet completely enclose the anther and ovary (Kirby and Appleyard, 1987). At the GA stage, the meristematic dome completes the initiation of floret primordia, so that after this stage no more floret primordia will be produced ; the glumes almost completely cover all but the tips of the florets. The spike length peaks at the YA stage (Guo et al., 2018); glumes are fully formed, and the lemmas of the first three florets are visible. At the TP stage, the first awn is visible (Zadoks et al., 1974), at HD stage, half of the spike emerges from the last leaf blade (Zadoks et al., 1974). Finally, at the AN stage, yellow anthers appear along the spike (Zadoks et al., 1974).Spike architecture is a complicated trait, that is determined by multiple factors. Spike fertility index (i.e. the ratio between grain number per spike and weight of spike chaff) is a critical metric of assimilate distribution between grains and spike chaff (e.g. glume, lemma, palea, rachis). Grain number per spikelet along the main inflorescence also influences spike shape. Spikelet density (the ratio between spike length and spikelet number) also indicates spike compactness. Spikelet fertility (the ratio between fertile and total spikelet number) informs on the proportion of aborted spikelets. In addition, grain size traits (thousand-kernel weight-TKW, grain area, grain width, grain le...

Effects of genetic components of plant development on yield-related traits in wheat (Triticum aestivum L.) under stress-free conditions

“…In the wheat PPD-D1 gene, it is the insensitivity allele that enhances plant development both under short and long photoperiods, which results in these pleiotropic effects ( Prieto et al., 2018 ). PPD1 may influence several yield-related traits including the seed number per ear and thousand kernel weight and, as a final result, grain yield itself, but the experimental data are more controversial in this aspect ( Liu et al., 2020 ; Gol et al., 2021 ; Jung et al., 2021 ; Achilli et al., 2022 ; Fernández-Calleja et al., 2022 ; Ding et al., 2022 ). The magnitude of the differences in yield-related traits between the insensitive and sensitive allele type groups may depend strongly on the type of the genetic populations (bi-, multiparental, or association panels) and/or on the environmental conditions of the experimental setup (controlled or field-grown experiments with seasonal and location effects in the case of the latter).…”

“…The start and speed of intensive stem elongation accelerate with a higher rate in insensitive genotypes as the ambient temperature level arises. Under favorable conditions, however, those same attributes can be disadvantageous for yield formation, which explains the strong environmental dependence of PPD1 on grain yield ( Liu et al., 2020 ). Thus, the indirect effects of PPD1 on yield-related traits may appear mostly as causal consequences of altered plant developmental patterns under unfavorable growing conditions that occur at any time from the start of the intensive stem elongation for any of the two PPD1 allele phases ( Fernández-Calleja et al., 2022 ).…”

“…Worland et al (1998) stated that photoperiod insensitivity may benefit grain yield in years and locations with hotter and drier summers. Several experiments revealed the importance of the PPD-D1 insensitivity allele in abiotic stress tolerance, mostly via avoiding the stressful periods through accelerated plant development, which led to earlier heading and ripening with a decreased seed number per spike and, in some cases, higher thousand kernel weight (Liu et al, 2020;Alipour and Abdi, 2021;Dreisigacker et al, 2021). In this process, not only is the photoperiod an important environmental indicator but also the ambient temperature during the phase of intensive stem elongation (Gonzaĺez et al, 2005b;Borraś-Gelonch et al, 2012;Kiss et al, 2017).…”

Pleiotropic effect of Ppd-D1a on earliness, yield and yield components of bread wheat under well-watered and rain-fed conditions

“…The effect of Ppd-D1a on grain yield is tightly dependent on target environment, so that Ppd-D1a associated with yield disadvantage in the UK (-1.8%) and yield advantage in Germany (+ 7.7%) and Yugoslavia (+ 33%) (Worland et al 1998). Moreover, insensitive allele to photoperiod, Ppd-D1a, affected grain yield in a range of + 3 to -5% under greenhouse condition (Liu et al 2020), and by 8.2 under eld condition in China (Chen et al 2018). On average, Ppd-D1a reduced heading time by 5.14 days via shortening the vegetative phase, in the present study.…”