Vegetative and early reproductive development as affected by allelic composition for Ppd-1 genes under contrasting photoperiod

THOMAS PEREZ GIANMARCO; SLAFER GA; GONZÁLEZ, FERNANDA G

Pergamino, Buenos Aires

Congreso; VIII Congreso Nacional de Trigo, VI Simposio de Cereales de Siembra otoño invernal, II Encuentro del Mercosur.; 2016

AIANBA-INTA-UNNOBA

Early development ofwheat?s life cycle is comprised by two subsequent phases: the vegetative phase(VP, that of leaf primordia generation), and the early reproductive phase (ERP,during which spikelets are differentiated). Together, they greatly define themoment of occurrence of important stages for crop?s adaptation, through traitsthat are known to be sensitive to variation in photoperiod: phases? durationand the rate at which structures are generated (plastochron-1) andexpanded (phyllochron-1), determining the number of them producedand appeared. Major genes Ppd-1modulate plant?s response to that environmental factor, but how their allelicvariants impact on developmental physiology is yet to be fully understood. Ourobjective was to assess the effect of three different alleles for Ppd-1 and their combination on certaindevelopmental variables: VP and ERP duration, first (mostly leaf) and second(mostly spikelet) rates of primordia generation, as well as time of change fromone to another, final leaf number (FLN) and the rate at which they appear andnumber of spikelets per spike (SPKLTS SPK-1). In order to achieveit, five near isogenic lines (NILs) carrying either three, one or noinsensitivity alleles from different donors were grown at constant temperature(16 °C) in two photoperiodic environments: 12 and 16 hours of light per day.External observations as well as periodic sample dissections for apical stateassessment (particularly, terminal spikelet stage (TS)) and primordia countwere made. These data were fitted on a bi-linear model for estimation ofprimordia generation rates and time of floral initiation (FI). Insensitivityalleles hastened development towards terminal spikelet (TS), shortening both VPand ERP for NILs carrying either of them and their combination, when grown inshort days. Some stronger alleles kept their effect under long days, as well.VP shortening was highly associated with lower FLN (r2=0,95, p<0,0001),while ERP variation only partially accounts for the differences in SPKLTS SPK-1.This is explained by the effect insensitivity alleles had on primordiadifferentiation dynamics: Not only did they advance the moment of highprimordia differentiation rates, but they also make it reach greater maximumvalues. On the other hand, they had no effect on the first, lower primordiadifferentiation rate, the one at which leaf primordia are produced. Long daysexert a similar effect to that of the strongest insensitivity, achieved bystacking three triple insensitive alleles. The magnitude of the insensitivityeffect carried by each allele differs according to the donor consistentlythrough variables. These results shall be compared to the ones obtained fromfield-grown experiments.