Genetic variation, heritability and genotype by environment interaction of morphological traits in a tetraploid rose population

Abstract

BackgroundGlobal trade has ensured that the ornamental horticulture continues to grow worldwide, with rose hybrids being the most economically important genus (Rosa x hybrida). Due to changes in global trade and an increase in energy costs the ornamental industry has seen a shift in the production and sale of flowers from the US and Europe alone to production in Africa and Latin America. As Kenya is a major exporter of roses to Europe we studied the genetic variation and heritability of specific morphological traits in a tetraploid population grown in the Netherlands and in Kenya. The aim was to estimate genotype by environment interaction (G × E) and to investigate the implications of (G × E) for rose breeding.ResultsA tetraploid rose population (K5) from a cross between two tetraploid parents was field tested over two seasons in the Netherlands (summer and winter) and two locations in Kenya (Nairobi and Njoro). Ten traits were compared per genotype across the four environments. There were differences in trait association across the four environments showing that the traits were partially influenced by the environment.The traits that had a low ratio of σ2ge/σ2g also showed a high value for heritability. For the traits number of petals, prickles on petioles, prickles on stems the interaction is minimal. For the traits chlorophyll content, stem width and side shoots we observed a much higher interaction ratio of 0.83, 1.43 and 3.13 respectively. The trait number of petals had the highest heritability of 0.96 and the lowest σ2ge/σ2g ratio (0.08). The trait number of side shoots (SS) with the lowest heritability (0.40) also had the highest σ2ge/σ2g ratio of 3.13.ConclusionAttained by this experiment showed that we have different magnitudes of non-crossover G × E interactions. For the traits number of petals, prickles on stems and prickles on petioles with a low interaction and high heritability, selection can be done at any of the environments. Thus, these traits can be confirmed at the breeding site. For the traits stem width, side shoots and chlorophyll content that had a higher interaction selection for or against these traits should be done at the production location or at least be verified there.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-014-0146-z) contains supplementary material, which is available to authorized users.

Genetic mapping in polyploids

“…P540 (the maternal parent) possesses dark red flowers, has prickles on both stem and petiole and is susceptible to powdery mildew, whereas P867 (paternal) has pale salmon-coloured flowers, few to no prickles and is more resistant to powdery mildew (Koning-Boucoiran et al, 2012;Gitonga et al, 2014). The F1 population resulting from this cross originally comprised of 181 individuals (Yan et al, 2006) but subsequently was found to consist of only 151 unique individuals after genotyping with the 68K WagRhSNP Axiom SNP array .…”

“…In the Netherlands, observations were made during both the summer of 2007 (WAG_S) and the winter of 2007 / 2008 (WAG_W) whereas in Kenya the observations were made during the period January -July 2009. Full details of plant propagation and growth conditions are described in Gitonga et al (2014). A description of the traits measured is provided in Supplementary Table 1.…”

“…One of the more important considerations is whether the reported QTL are robust across environments or are only expressed in a specific environment. This is particularly relevant for modern rose breeding, for which the selection and production environments often differ (Gitonga et al, 2014). In this study we analysed phenotypic data from three locations, two in Kenya and one in the Netherlands, with an extra set of phenotypes evaluated during both a summer and winter season in the Netherlands.…”

“…These traits were assessed in different locations, enabling an investigation of possible genotype x environment interactions (Gitonga et al, 2014). This is of particular relevance in modern-day ornamental breeding, where selection and production are often performed in different locations (for details see Gitonga et al (2014)). Stability of QTL expression over both selection and target environments is needed if marker-assisted selection is to be effectively applied.…”

“…Stability of QTL expression over both selection and target environments is needed if marker-assisted selection is to be effectively applied. Here, we re-analyse the data of Gitonga et al (2014) to perform a QTL analysis using the recently-published high-density tetraploid rose linkage map (containing over 25K single-nucleotide polymorphism (SNP) markers ). Our current study helps to increase our understanding of the genetic control of these traits in tetraploid rose, as well as testing and exploring the effectiveness of recently-developed methods (Chapter 8) for the genetic analysis of autopolyploids.…”