Allelic variation in major genes (rht-b1, ppd-a1 and vrn-a1) and its effect on plant height, peduncle length and flowering/heading date in a durum wheat collection under field conditions

Abstract

Heading date is an important trait in wheat breeding as it aff ects adaptati on and yield potenti al. Selecti on for height and the introducti on of semi-dwarfi ng alleles at the Rht loci have been proven to be eff ecti ve for wheat yield improvement. The aim of this work was to analyze the allelic variati on in three major genes (Rht-B1, Ppd-A1 and Vrn-A1) in a durum wheat collecti on (Triti cum turgidum L. var durum) and its phenotypic eff ects. Field trials were conducted during 2011 (133 entries, 2 environments), 2013 (168 entries, 2 environments) and 2014 (168 entries, 5 environments) using an alpha-latti ce stati sti cal design, in 5 assays. The genotyping was performed using the KASPTM genotyping technology and four single nucleoti de polymorphisms (SNP) were detected in the 168 durum wheat genotypes. The eff ect of the allelic variati on in these loci on the phenotype was assessed by using the ANOVA test, considering diff erent number of fi eld evaluati ons for each trait: peduncle length (4), plant height (5), spikes/m2 (5) heading date (8) and fl owering ti me (1). The semi-dwarfi ng allele (Rht-B1b) was carried by 85.5% of the analyzed materials, showing a signifi cant eff ect in all the environments with an average reducti on in plant height (-23.6%) and peduncle length (-33.3%), but not showing a signifi cant eff ect on the number of spikes/m2 . Regarding to the heading date/fl owering ti me traits, a relati ve high frequency of the spring allele Vrn-A1b (11.3%) at the Vrn-A1 locus (Marquis allele) and three alleles at the photoperiod A1 locus (Ppd-A1) (the deleted types `GS-100´, `GS-105´ and the intact allele) were detected. The combinati on of Vrn-A1b/ intact sequence alleles (11.3%) for the haplotype Vrn-A1/Ppd-A1 showed, in average, a delay of 9.5 days in heading date respect to the genotypes carrying the `GS-100´ photoperiod insensiti ve allele. These are interesti ng results to be used for MAS in nati onal durum breeding programs.