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

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 intro- gressed 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 ini- tiation. 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 spike- let number.

Funding was provided by ADAPTAWHEAT (a project funded by the European Commission under the 7th Framework Programme for Research and Technological Development) and by project AGL2012- 35300 funded by the Ministry of Economy and Competitiveness of Spain. HO held a FPI scholarship from the Spanish Ministry of Science and Innovation, and PP held a PhD scholarship from the University of Lleida. We thank Andreu Casellas for excellent technical assistance and Ignacio Romagosa for valuable advice on the statistical procedures.