Effect of Flowering Time-Related Genes on Biomass, Harvest Index, and Grain Yield in CIMMYT Elite Spring Bread Wheat

Grain yield (YLD) is a function of the total biomass (BM) and of partitioning the biomass by grains, i.e., the harvest index (HI). The most critical developmental stage for their determination is the flowering time, which mainly depends on the vernalization requirement (Vrn) and photoperiod sensitivity genes (Ppd) loci. Allelic variants at the Vrn, Ppd, and earliness per se (Eps) genes of elite spring wheat genotypes included in High Biomass Association Panel (HiBAP) I and II were used to estimate their effects on the phenological stages BM, HI, and YLD. Each panel was grown for two consecutive years in Northwest Mexico. Spring alleles at Vrn-1 had the largest effect on shortening the time to anthesis, and the Ppd-insensitive allele Ppd-D1a had the most significant positive effect on YLD in both panels. In addition, alleles at TaTOE-B1 and TaFT3-B1 promoted between 3.8% and 7.6% higher YLD and 4.2% and 10.2% higher HI in HiBAP I and II, respectively. When the possible effects of the TaTOE-B1 and TaFT3-B1 alleles on the sink and source traits were explored, the favorable allele at TaTOE-B1 showed positive effects on several sink traits mainly related to grain number. The favorable alleles at TaFT3-B1 followed a different pattern, with positive effects on the traits related to grain weight. The results of this study expanded the wheat breeders’ toolbox in the quest to breed better-adapted and higher-yielding wheat cultivars.

Photoperiod-sensitivity genes (Ppd-1): Quantifying their effect on the photoperiod response model in wheat

Coupling anthesis date to the best environment is critical for wheat (Triticum aestivum L.) adaptation and yield potential. Development to anthesis is controlled by temperature and photoperiod. Response to photoperiod is chiefly modulated by Ppd-1 genes, but their effect on the quantitative response of i) time to anthesis, and ii) pre-anthesis phases to photoperiod remains largely unknown. A photoperiod-sensitive spring cultivar, Paragon, and near-isogenic lines of it carrying different combinations of Ppd-1a insensitivity alleles were tested under a wide range of photoperiods, including switches in photoperiod at the onset of stem elongation. Using multimodel inference we found that Ppd-1a alleles reduced photoperiod sensitivity from a) emergence to anthesis and b) emergence to onset of stem elongation, both in a less than additive manner, while threshold photoperiod and intrinsic earliness were unaffected. Sensitivity to current photoperiod from onset of stem elongation to flag leaf and from then to anthesis was milder than for previous phases and was not related to variability in Ppd-1. But ‘memory’ effects of previously experienced photoperiod on the duration from onset of stem elongation to flag leaf, was. The characterisation and quantification provided here of Ppd-1 allelic combinations’ effects on development should help increase genotype-to-phenotype models’ accuracy for predicting wheat phenology.

PCR-analysis of photoperiod sensitivity genes in bread wheat varieties from Bilatserkovska experimental breeding station

The aim. Determination of alleles of the photoperiod sensitivity genes Ppd-1 in 16 winter wheat varieties of the Bilatserkovska Experimental Breeding Station and identification of the haplotypes of Ppd-D1 gene according to the accepted classification. Methods. DNA isolation, allele-specific and nested PCR, electrophoresis in agarose and polyacrylamide gels, determination of the significant differences in the time of heading. Results. Plants of the varieties Vodohrai bilotserkivs’kiy; Bilotserkivs’ka napivkarlykova, Olesia, Perlyna lisostepu, Elehiia, Yasochka, Lybid’, Tsarivna, Lisova pisnia, Romantyka, Vidrada, Schedra nyva, Charodiika bilotsekivs’ka, Russa, Driada 1 have the genotype PpdA1b Ppd-B1b Ppd-D1a and belong to the VII haplotype of the Ppd-D1 gene. The genotype of the variety Legenda bilotsekivs’ka is characterized by the presence of the alleles Ppd-A1b Ppd-B1b Ppd-D1b and belongs to the IV haplotype of the Ppd-D1 gene. The significant differences (P = 0.01) in the time of heading was detected only between the varieties Russa and Legenda bilotsekivs’ka and was 12.4 days. Conclusions. Most BEBS varieties are characterized by genotype — PpdA1b Ppd-B1b Ppd-D1a, in which the allele Ppd-D1a determines insensitivity to the photoperiod and leads to early heading. Only variety Legenda bilotsekivs’ka is the carrier of the recessive allele of Ppd-D1 gene, belongs to the IV haplotype, has the latest time of heading. Keywords: Ppd-A1, Ppd-B1, Ppd-D1 genes, winter wheat, PCR analysis, photoperiod sensitivity.

Wheat pre-anthesis development as affected by photoperiod sensitivity genes (Ppd-1) under contrasting photoperiods

Fine tuning wheat phenology is of paramount importance for adaptation. A better understanding of how genetic constitution modulates the developmental responses during pre-anthesis phases would help to maintain or even increase yield potential as temperature increases due to climate change. The photoperiod-sensitive cultivar Paragon, and four near isogenic lines with different combinations of insensitivity alleles (Ppd-A1a, Ppd-B1a, Ppd-D1a or their triple stack) were evaluated under short (12 h) and long (16 h) photoperiods. Insensitivity alleles decreased time to anthesis and duration of the three pre-anthesis phases (vegetative, early reproductive and late reproductive), following the Ppd-D1a > Ppd-A1a > Ppd-B1a ranking of strength. Stacking them intensified the insensitivity, but had no additive effect over that of Ppd-D1a. The late reproductive phase was the most responsive, even exhibiting a qualitative response. Leaf plastochron was not affected but spikelet plastochron increased according to Ppd-1a ranking of strength. Earlier anthesis resulted from less leaves differentiated and a fine tuning effect of accelerated rate of leaf appearance. None of the alleles affected development exclusively during any particular pre-anthesis phase, which would be ideal for tailoring time to anthesis with specific partitioning of developmental time into particular phases. Other allelic variants should be further tested to this purpose.