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

Abstract

Abstract Early heading is a very important character for bread wheat cultivated under end season heat and drought stress conditions. Heading time is influence by three groups of genes including photoperiod (Ppd), vernalization (Vrn) and earliness per se (Eps). Among the identified genes for heading time, Ppd- D1 is the only gene that worth marker assisted selection/backcrossing. Despite of recognized effect of Ppd-D1a on earliness, its effect on yield, yield component and important agronomic traits is under debate. In the present research, near isogenic lines were developed for Ppd-D1a in two genetic backgrounds, Roshan and Kalheydari, to investigate the precise pleiotropic effect of Ppd-D1a on yield and yield components of bread wheat. Two pairs of isogenic lines were assessed under rain-fed and well-watered conditions in Kerman and Sepidan during two successive growing seasons, 2020–2021 and 2021–2022. Compared to photoperiod sensitive allele (Ppd-D1b), photoperiod insensitive allele (Ppd-D1a) reduced days to heading and ripening by 5.14 and 7.53 days, respectively. Results also showed that Ppd-D1a improved 1000-grain weight (+ 17%) and decreased grains number per spike (-14%) to finally improve grain yield under rain-fed conditions (+ 13%). However, Ppd-D1a had a different effect on the mentioned traits under well-watered conditions where decreased 1000-grain weight (-18%) and improved grains number per spike (+ 10%) with insignificant effect on grain yield. These findings showed that pleotropic effect of Ppd-D1a on yield and yield component strongly depends on target environment.