Dynamics of leaf and spikelet primordia initiation in wheat as affected by Ppd-1a alleles under field conditions.

Helga Ochagavía,Gustavoa Slafer,Paula Prieto,Roxana Savin,Simon Griffiths

doi:10.1093/jxb/ery104

Helga Ochagavía, Gustavoa Slafer + Show 3 more

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https://doi.org/10.1093/jxb/ery104

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Abstract

Wheat adaptation is affected by Ppd genes, but the role of these alleles in the rates of leaf and spikelet initiation has not been properly analysed. Twelve near isogenic lines (NILs) combining Ppd-1a alleles from different donors introgressed in A, B, and/or D genomes were tested under field conditions during two growing seasons together with the wild type, Paragon. Leaf initiation rate was unaffected by Ppd-1a alleles so the final leaf number (FLN) was reduced in parallel with reductions in the duration of the vegetative phase. Spikelet primordia initiation was accelerated and consequently the effect on spikelets per spike was less than proportional to the effect on the duration of spikelet initiation. The magnitude of these effects on spikelet plastochron depended on the doses of Ppd-1 homoeoalleles and the specific insensitivity alleles carried. Double ridge was consistently later than floral initiation, but the difference between them was not affected by Ppd-1a alleles. These findings have potential for selecting the best combinations from the Ppd-1 homoeoallelic series for manipulating adaptation taking into consideration particular effects on spikelet number.

Highlights

Flowering time is critical for adaptation of wheat to the many regions in which it is grown (Braun et al, 2010)
In order to validate our determinations made from individual plants of each plot sampled repeatedly through the growing season, we compared the number of spikelets per spike determined through the dynamics of primordia initiation with the same variable measured in the plot sample taken at anthesis.We observed that the number of spikelets per spike determined averaging the many individual plants we sampled from terminal spikelet to anthesis was the same value that we determined in the larger sample taken at anthesis
The rate of primordia production and its reciprocal were calculated from plotting the total number of primordia against thermal time for each particular genotype and in each growing season.The relationships are illustrated for the average of all near isogenic line (NIL) with single, double, or triple doses of Ppd-1a alleles always compared with wild-type Paragon with Ppd-1b alleles in all three genomes (Fig. 3), but the reciprocal of both slopes are offered for each individual case (Table 2)

Summary

Introduction

Flowering time is critical for adaptation of wheat to the many regions in which it is grown (Braun et al, 2010). Flowering time involves three major phenological phases: vegetative, early reproductive, and late reproductive phases (Slafer and Rawson, 1994a). During these phases, the organs that will become the main sources and sinks of the crop, whose balance will determine yield, are initiated as primordia. In addition to those that are already differentiated in the embryo of the grain (~4), are developed during the vegetative phase.All spikelet primordia are initiated during the early reproductive phase and all florets are produced within the spikelets during the late reproductive phase (Slafer et al, 2015). The dynamics of initiation of leaves and spikelets and that of florets are dramatically different. We will focus on the dynamics of leaf and spikelet initiation and, in a companion

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