Evaluation of the Allelic Variations in Vernalisation (VRN1) and Photoperiod (PPD1) Genes and Genetic Diversity in a Spanish Spelt Wheat Collection

Abstract

Allelic variation within genes controlling the vernalisation requirement (VRN1) and photoperiod response (PPD1) determines the adaptation of wheat to different environmental growing conditions as well as influences other traits related to grain yield. This study aimed to screen a Spanish spelt wheat collection using gene-specific molecular markers for VRN-A1, VRN-B1, VRN-D1, and PPD-D1 loci and to phenotype for heading date (HD) in both field and greenhouse experiments under a long photoperiod and without vernalisation. Fifty-five spelt genotypes (91.7%) exhibited a spring growth habit, and all of them carried at least one dominant VRN1 allele, whereas five (8.3%) genotypes had a winter growth habit, and they carried the triple recessive allele combination. The Vrn-D1s was the most frequent allele in the studied set of spelt accessions, and it was found in combination with both the dominant Vrn-A1b and/or Vrn-B1a alleles in 88.3% of the spelt accessions tested. All spelt accessions carried the photoperiod-sensitive Ppd-D1b allele, which may explain the late heading of spelt germplasm compared to the commercial spring bread wheat Setenil used as a control. The least significant difference test showed significant differences between allelic combinations, the earliest accessions being those carrying two or three dominant alleles, followed by the one-gene combinations. In addition, the genetic diversity was evaluated through capillary electrophoresis using 15 wheat simple sequence repeat (SSR) markers. Most markers had high levels of polymorphism, producing 95 different alleles which ranged between 53 and 279 bp in size. Based on the polymorphic information content values obtained (from 0.51 to 0.97), 12 out of the 15 SSRs were catalogued as informative markers (values > 0.5). According to the dendrogram generated, the spelt accessions clustered as a separate group from the commercial bread wheat Setenil. Knowledge of VRN1 and PPD1 alleles, heading time, and genetic variability using SSR markers is valuable for spelt wheat breeding programs.

Keywords: flowering time; genetic diversity; photoperiod; spelt; vernalisation; wheat.

Figure 1

PCR amplification using allele-specific primers for VRN-A1, VRN-B1, VRN-D1, and PPD-D1 loci of different spelt genotypes. (a) primers VRN1-AF and VRN1-INT1R to detect dominant Vrn-A1a and Vrn-A1b and recessive vrn-A1 alleles of the VRN-A1 gene; (b) MspI restriction patterns of the corresponding PCR products in Figure 1a, separated by polyacrylamide gels; (c) primers Intr1/B/F, Intr1/B/R3, and Intr1/B/R4 to detect Vrn-B1a, Vrn-B1b, and vrn-B1 alleles of the VRN-B1 gene; (d) primers Intr1 and Intr1/B/R3 to detect Vrn-B1a and Vrn-B1c alleles; (e) primers Intr1/D/F, Intr1/D/R3, and Intr1/D/R4 to detect Vrn-D1a, Vrn-D1s, and vrn-D1 alleles of the VRN-D1 gene; (f) Intr1/D/F and INSD-R primers specific to the Vrn-D1s allele; (g) primers Ppd-D1_F, Ppd-D1_R1, and Ppd-D1_R2 to detect dominant Ppd-D1a photoperiod-insensitive and recessive Ppd-D1b photoperiod-sensitive alleles of the PPD-D1 gene. Common wheat cultivars Chinese Spring (CS), Mara, Cadet, Paragon, and Escacena were used as controls.

Figure 2

Distribution of spelt wheats by heading date under greenhouse (blue columns) and field (green columns) conditions, respectively.

Figure 3

UPGMA dendrogram obtained from cluster analysis of 60 Spanish spelt wheat accessions based on the Dice similarity coefficient using 15 SSR markers.