Efecto del gen Ppd-1 en la determinación del rendimiento del trigo bajo diferentes condiciones de fotoperíodo

Photoperiod is one of the main environmental factors regulating wheat (Triticum aestivum L.) development, determining the timing of flowering and the duration of phenological phases. The response to this factor is primarily regulated by the homologous loci of the Ppd-1 gene, located in the A, B, and D subgenomes of the hexaploid genome. Insensitivity alleles promote flowering under short-day conditions, shortening the crop cycle independently of the ambient photoperiod, whereas sensitivity alleles require long days to trigger the transition to the reproductive phase. Although the effect of Ppd-1 on phenology is well documented, its influence on grain yield and the possible existence of direct pleiotropic effects independent of cycle duration remain open questions. This study aimed to evaluate the effect of Ppd-1 alleles in the B and D subgenomes on wheat phenology and grain yield using near-isogenic lines under contrasting photoperiod conditions. The experiment was conducted at the La Estanzuela Experimental Station of the National Institute of Agricultural Research (INIA) during the 2025 growing season. Three sets of near-isogenic lines representing three genotypes, sensitive, insensitive-B, and insensitive-D, were evaluated under natural photoperiod and extended photoperiod (24 hours of continuous light via artificial illumination). Recorded variables included the duration of phenological phases expressed as thermal time to first node (Z3.1), anthesis (Z6.5), and physiological maturity (Z8.7), grain yield, and its components: spikes per m⁻², grains per spike, and grain weight. Linear mixed models with Tukey comparisons and an analysis of covariance (ANCOVA) were applied to determine whether the effects on yield are mediated by phenology or reflect direct pleiotropic effects of the gene. Under natural photoperiod, insensitivity alleles significantly reduced the duration of the cycle to flowering, following a hierarchy consistent with the literature: Ppd-D1 produced a greater shortening (536 °Cd less than the sensitive genotype) than Ppd-B1 (426 °Cd less). Under extended photoperiod, this difference between insensitive genotypes disappeared, as continuous light exposure generated a maximal inductive stimulus that abolished the advantage of the Ppd-D1 allele for flowering under short days. Phenological differences translated into yield variation primarily through the number of grains per spike: the sensitive genotype showed the highest yield under natural photoperiod (4921 kg ha⁻¹) with 37.6 grains per spike, while the insensitive-D genotype recorded the lowest yield (2982 kg ha⁻¹) with 24.9 grains per spike. Grain weight was not significantly affected by genotype or photoperiod. The ANCOVA did not provide conclusive evidence for direct pleiotropic effects of Ppd-1 on yield: the genotype factor was not significant in the model, and the statistical power of the design is sufficient to rule out the pleiotropy of the Ppd-1 gene on performance. These results confirm that Ppd-1 modulates wheat yield primarily through its effect on the duration of the critical period and the number of grains per spike, with quantitatively relevant differences between alleles under natural photoperiod. In the Uruguayan productive context, the insensitive-B genotype represents the most balanced option between earliness and yield potential when cycle shortening is required, without statistically differing from the sensitive genotype in productivity.