Genotype-by-environment interactions affecting heterosis in maize

Abstract

The environment can influence heterosis, the phenomena in which the offspring of two inbred parents exhibits phenotypic performance beyond the inbred parents for specific traits. In this study we measured 25 traits in a set of 47 maize hybrids and their inbred parents grown in 16 different environments with varying levels of average productivity. By quantifying 25 vegetative and reproductive traits across the life cycle we were able to analyze interactions between the environment and multiple distinct instances of heterosis. The magnitude and rank among hybrids for better-parent heterosis (BPH) varied for the different traits and environments. Across the traits, a higher within plot variance was observed for inbred lines compared to hybrids. However, for most traits, variance across environments was not significantly different for inbred lines compared to hybrids. Further, for many traits the correlations of BPH to hybrid performance and BPH to better parent performance were of comparable magnitude. These results indicate that inbred lines and hybrids show similar trends in environmental response and both are contributing to observed genotype-by-environment interactions for heterosis. This study highlights the degree of heterosis is not an inherent trait of a specific hybrid, but varies depending on the trait measured and the environment where that trait is measured. Studies that attempt to correlate molecular processes with heterosis are hindered by the fact that heterosis is not a consistent attribute of a specific hybrid.

Highly Genotype- and Tissue-specific Single-Parent Expression Drives Dynamic Gene Expression Complementation in Maize Hybrids

“…Furthermore, the enrichment of non-syntenic genes in non-PAV SPE and PAV SPE gene sets, along with the enrichment for expression complementation in the hybrids across genotypes and tissues for these genes, could contribute to the superior adaptation of hybrid plants to environmental stresses. The high genotype-and tissuespecific nature of non-PAV SPE and PAV SPE genes could also contribute to the diversified manifestation of heterosis across traits, environments, and genetic combinations (Flint-Garcia et al, 2009;Schnable and Springer, 2013;Marcon et al, 2017;Li et al, 2018).…”

“…Modern maize production has benefited from heterosis, a widely observed phenomenon in which hybrids show superior performances relative to their inbred parents (Flint-Garcia et al, 2009;Birchler et al, 2010). However, the manifestation of heterosis has been shown to vary greatly across traits and environments for a given hybrid (Flint-Garcia et al, 2009;Li et al, 2018), making it unlikely to be explained by a single mechanism. Indeed, the molecular underpinnings for heterosis are still under debate (Schnable and Springer, 2013;Wallace et al, 2018).…”

Using yield quantitative trait locus targeted SSR markers to study the relationship between genetic distance and yield heterosis in upland cotton (Gossypium hirsutum)

“…A favourable environment will result in higher outputs, whereas under stress conditions a greater amount of energy is utilized to adapt to the adverse conditions. In maize, it has also been observed that environment influences the degree of heterosis for yield traits (Li et al, 2018). The latter authors concluded that environment is critical and affects the degree of heterosis for a trait within a genotype.…”

“…This difference might be due to the concept of "buffering," which posits that a heterozygous population shows higher stability than a homozygous population. A hybrid's response to environmental stimuli will result in an altered degree of heterosis across different environments (Allard & Bradshaw, 1964;Li et al, 2018). In addition, seed cotton yield is a multiplicative trait to which many other individual traits contribute; therefore, it is unlikely that all traits of a genotype will perform identically in different environments.…”

Characterizing allele-by-environment interactions using maize introgression lines

“…Although G×E has been well-documented and studied in plant and animal species, it remains a significant challenge to breeding programs (Crossa 2012; de Leon et al 2016; Xu 2016; Li et al 2018). Obtaining a rigorous assessment of G×E effects requires phenotypic evaluation in a wide range of environments and breeder choices about the level of trait instability across environments that will be tolerated.…”