Photoperiod-sensitivity genes shape floret development in wheat.

Thomas I Pérez-Gianmarco,Fernanda G González,Gustavo A Slafer

doi:10.1093/jxb/ery449

Abstract

Lengthening the pre-anthesis period of stem elongation (or late-reproductive phase, LRP) through altering photoperiod sensitivity has been suggested as a potential means to increase the number of fertile florets at anthesis (NFF) in wheat. However, little is known about the effects that the Ppd-1 genes modulating plant response to photoperiod may have on reproductive development. Here, five genotypes with either sensitive (b) or insensitive (a) alleles were grown in chambers under contrasting photoperiods (12 h or 16 h) to assess their effects. The genotypes consisted of the control cultivar Paragon (three Ppd-1b) and four near-isogenic lines of Paragon with Ppd-1a alleles introgressed from: Chinese Spring (Ppd-B1a), GS-100 (Ppd-A1a), Sonora 64 (Ppd-D1a), and Triple Insensitive (three Ppd-1a). Under a 12-h photoperiod, NFF in the genotypes followed the order three Ppd-1b > Ppd-B1a > Ppd-A1a > Ppd-D1a > three Ppd-1a. Under a 16-h photoperiod the differences were milder, but three Ppd-1b still had a greater NFF than the rest. As Ppd-1a alleles shortened the LRP, spikes were lighter and the NFF decreased. The results demonstrated for the first time that Ppd-1a decreases the maximum number of florets initiated through shortening the floret initiation phase, and this partially explained the variations in NFF. The most important impact of Ppd-1a alleles, however, was related to a reduction in survival of floret primordia, which resulted in the lower NFF. These findings reinforce the idea that an increased duration of the LRP, achieved through photoperiod sensitivity, would be useful for increasing wheat yield potential.

Highlights

The yield potential of wheat (Triticum aestivum) is closely 1989; González et al, 2003b) and that yield is mostly sinkrelated to the number of fertile florets at anthesis (NFF), given limited during grain filling (Fischer, 2007; Serrago et al, 2008; that most fertile florets set grains (Fischer, 1983; Siddique et al, González et al, 2014)
The results demonstrated for the first time that Ppd-1a decreases the maximum number of florets initiated through shortening the floret initiation phase, and this partially explained the variations in NFF
The duration of the late-reproductive period (LRP) was altered by Ppd-B1, but no impact on spike dry weight at anthesis (SDWa) was observed, resulting in no response in fertile florets per spike when compared to photoperiod-sensitive lines.The second report (Prieto et al, 2018) explored more combinations of Ppd-1a alleles, including Ppd-A1a for the first time.This study showed that, in general, the presence of Ppd-1a alleles reduced floret fertility, mainly associated with floret survival, but the results were not fully consistent between growing seasons

Summary

Introduction

The yield potential of wheat (Triticum aestivum) is closely 1989; González et al, 2003b) and that yield is mostly sinkrelated to the number of fertile florets at anthesis (NFF), given limited during grain filling (Fischer, 2007; Serrago et al, 2008; that most fertile florets set grains (Fischer, 1983; Siddique et al, González et al, 2014). Depending on the position of the spikelet within the spike, between 6 to 12 floret primordia per spikelet are initiated (Langer and Hanif, 1973; Sibony and Pinthus, 1988) but usually only 30–45% reach the fertile floret stage (Langer and Hanif, 1973; Kirby, 1988; González et al, 2011).The availability of assimilates for spike growth during the pre-anthesis period of stem elongation, when florets develop, determines floret survival (Fischer and Stockman, 1980; Kirby, 1988; Ghiglione et al, 2008; González et al, 2011; Ferrante et al, 2013). More in-depth research has shown that photoperiod affects the dynamics of floret development: the shorter the photoperiod, the longer the duration of floret development, which allows some labile florets to complete their development, increasing spike fertility (Craufurd and Cartwright, 1989; Miralles et al, 2000; González et al, 2003a, 2005b)

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