Dynamics of floret initiation/death determining spike fertility in wheat as affected by Ppd genes under field conditions

Abstract

As wheat yield is linearly related to grain number, understanding the physiological determinants of the number of fertile florets based on floret development dynamics due to the role of the particular genes is relevant. The effects of photoperiod genes on dynamics of floret development are largely ignored. Field experiments were carried out to (i) characterize the dynamics of floret primordia initiation and degeneration and (ii) to determine which are the most critical traits of such dynamics in establishing genotypic differences in the number of fertile florets at anthesis in near isogenic lines (NILs) carrying photoperiod-insensitive alleles. Results varied in magnitude between the two growing seasons, but in general introgression of Ppd-1a alleles reduced the number of fertile florets. The actual effect was affected not only by the genome and the doses but also by the source of the alleles. Differences in the number of fertile florets were mainly explained by differences in the floret generation/degeneration dynamics, and in most cases associated with floret survival. Manipulating photoperiod insensitivity, unquestionably useful for changing flowering time, may reduce spike fertility but much less than proportionally to the change in duration of development, as the insensitivity alleles did increase the rate of floret development.

We are grateful to the team of the Crop Physiology Lab of the UdL for their technical assistance, especially to Andreu Casellas and Ignacio Romagosa for valuable advice on the statistical procedures. Funding was provided by ADAPTAWHEAT, an EU project, and the Ministry of Economy and Competitiveness of Spain project AGL2012-35300. PP and HO held scholarships from the University of Lleida and the Spanish Ministry of Science, respectively.