Pyramiding wheat pre-harvest sprouting resistance genes in triticale breeding

Abstract

Pre -harvest sprouting (PHS) is an important problem in cereal production reducing yield and grain quality. After decades of improvement, triticale remains particularly susceptible to PHS but no resistance genes or QTLs were identified so far in this species. As wheat shares the A and B genomes with triticale, wheat PHS resistance genes can be introgressed into triticale genome by recombination after interspecific crosses. In this project, three PHS resistance genes have been transferred from wheat to triticale by marker-assisted interspecific crosses, followed by four backcrosses. The gene TaPHS1 from the 3AS chromosome of cultivar Zenkoujikomugi (Zen) and the TaMKK3 and TaQsd1, respectively located on the 4AL and 5BL chromosomes derived both from cultivar Aus1408, were pyramided in the triticale cultivar Cosinus. Only the TaPHS1 gene increases consistently the PHS resistance in triticale. The lack of efficacy of the other two genes, especially TaQsd1, could be the result of an imperfect linkage between the marker and the gene of interest. The introduction of PHS resistance genes did not alter agronomic nor disease resistance performances of triticale. This approach leads to two new, agronomically performant and PHS-resistant triticale cultivars. Today, two breeding triticale lines are ready to enter the official registration process.

Keywords: Breeding; Pre-harvest sprouting; TaMKK3; TaPHS1; TaQsd1; Triticale.

Fig. 1

PCR profile showing the polymorphism between the parental lines (Aus1408, Zen, Cosinus), the lines with particular PHS resistance QTLs derived from the genotypes 47 and 54 and the breeding lines using the primers: A/ barc57 for TaPHS1 (3AS), B/ ZXQ118 for TaMKK3 (4AL) and wmc783 for TaQsd1 (5BL)

Fig. 2

Diagram showing steps involved in the production of lines used for the evaluation of PHS resistance QTLs effect and for marker-assisted breeding for PHS resistance. 3AS, 4AL and 5BL represent the QTLs for PHS resistance located on the 3AS, 4AL et 5BL chromosomes. Except for the plants ZAC (3 heterozygous QTLs), the lines are homozygous for the mentioned QTLs

Fig. 3

PHS assessment experiment. Almost 200 lines are tested in parallel in a shaded glasshouse. The picture shows emerging plantlets 14 days after the harvest

Fig. 4

Comparison of methods for PHS resistance evaluation. The PHS resistance is expressed with the SGI data (yellow), the number of seedlings per number of spikelets (green) or per number of seeds (blue) after 8 days. The evaluated lines represent the progeny of the genotype 47

Fig. 5

Effect of wheat PHS resistance QTLs on Triticale sprouting. SGI is calculated on data scored during 14 days. PHS resistance on genotype 47 (blue) and 54 (green) were evaluate in 2016 (light bars) and in 2018 (dark bars). Comparisons of means by genotype with letters (genotype 47 in black and 54 in red). Means that do not share a letter are significantly different. Grouping information using Tukey’s method and 95% confidence

Fig. 6

Effect of wheat PHS resistance QTLs on Triticale sprouting. SGI (bars) and WGI at 30 °C (dots) represent the average data from each QTLs combinations collected in 2016 and 2018 with genotype 47 (blue) and 54 (yellow). Vertical bars: standard deviation

Fig. 7

Scatterplot showing the Pearson’s correlation between PHS severity (SGI) and WGI at 30 °C

Fig. 8

Breeding for PHS resistance. The bars represent yield expressed in percentage of standard varieties (Balino, Trialdo, Larossa, and Cosinus) during 4 years of experiments (2017 to 2020). The blue curves show the PHS resistance expressed in SGI and the yellow curve is the percentage of WGI when WGI at 30 °C is compared to WGI at 10 °C (100%)