Response of PPD genes to photoperiod treatments during pre and post beginning of stem elongation

GONZALEZ FERNANDA G; MORAN AGUSTIN

Workshop; II Workshop Internacional de Ecofisologia de Cultivos aplicada al mejoramiento vegetal; 2013

The genes controlling the time to flowering in wheat are associated with yield potential of cultivars through two different ways: (i) defining the general adaptation of the cultivars to the environment explored around anthesis, which is crucial to grain number determination (the most important component associated with yield potential), and (ii) controlling the relative duration of stem elongation within the time to flowering, which has been proposed as an alternative to improve cultivar´s yield potential, as longer relative duration would result in higher grain number. The Ppd genes (Ppd-D1, Ppd-B1 and Ppd-A1), mapping in the group 2 chromosomes, control the response to photoperiod (wheat is a long day plant). The impact of these genes on time to flowering has been described but their effect on particular phases (emergence-beginning of stem elongation ?EM-SE- and beginning of stem elongation-anthesis -SE-AT-) has not been well documented. Five isogenic lines and the control cultivar Paragon (UK spring cultivar), differing in Ppd constitution and donors of the Ppd alleles, were sown in pots under field conditions in the Experimental Research Station of Pergamino, INTA. Different photoperiod treatments were applied during EM-SE/SE-AT: 0/0, 0/6, 6/0, 6/6, being 0 the natural photoperiod of the growing season and 6 an extension of six hours over that natural photoperiod. Photoperiod sensitivity of time to anthesis ranged from    -165ºCd/h when the three Ppd genes were in recessive state (r2= 62%, p=0.06) to        -48ºCd/h when the Ppd-D1 was in dominant state (r2= 90%, p<0.05). The EM-SE phase responded to photoperiod independently of the state of the alleles (p<0.05), but the magnitude of response was higher when the three alleles were recessive. Although a small response was observed during SE-AT in all the lines when the photoperiod was extended, the response was higher and significant (p<0.05) only when the three alleles were in recessive state.