Maternal Effects on Seed and Seedling Phenotypes in Reciprocal F1 Hybrids of the Common Bean (Phaseolus vulgaris L.)

Abstract

Maternal control of seed size in the common bean provides an opportunity to study genotype-independent seed weight effects on early seedling growth and development. We set out to test the hypothesis that the early heterotrophic growth of bean seedlings is determined by both the relative amount of cotyledon storage reserves and the genotype of the seedling, provided the hybrid genotype could be fully expressed in the seedlings. The hypothesis was tested via comparison of seed weight and seedling growth phenotypes of small-seeded (wild, ~0.10 g) and large-seeded (landrace, ~0.55 g) parents and their reciprocal F1 hybrids. Akaike's Information Criteria were used to estimate growth parameters and identify the phenotypic model that best represented the data. The analysis presented here indicates that the hybrid embryo genotype is not fully expressed during both seed and seedling growth and development. The analysis presented here shows that seed growth and development are controlled by the sporophyte. The strong similarity in seed size and shape of the reciprocal hybrid seed with seeds of the maternal parents is evidence of this control. The analysis also indicates that since the maternal sporophyte controls seed size and therefore the amount of cotyledon reserves, the maternal sporophyte indirectly controls early seedling growth because the cotyledons are the primary nutrient source during heterotrophic growth. The most interesting and surprising results indicated that the maternal effects extended to the root architecture of the reciprocal hybrid seedlings. This phenomenon could not be explained by seed size, but by alterations in the control of the pattern of gene expression of the seedling, which apparently was set by a maternally controlled mechanism. Although seed weight increase was the main target of bean domestication, it also had positive repercussions on early-growth traits and stand establishment.

Developmental Pleiotropy Shaped the Roots of the Domesticated Common Bean (Phaseolus vulgaris)

“…PCA results could be biased because seed weight was the main target of selection during domestication, and we have shown that seed reserves can significantly influence early heterotrophic growth (Singh et al, 2017). Thus, seed weight differences between wild and domesticated accessions could explain some of the root growth differences between the accessions as suggested by the significant phenotypic correlations between seed weight and many root traits, and root size traits in particular ( Supplemental Tables S3 and S4).…”

“…A RIF with 186 genotypes (F 6:8 ) was generated from a cross between a landrace (G19833) from Northwestern Peru (6.27°S, 77.75°W) and a wild accession (G23419) from Central Peru (11.23°S, 75.53°W). The two genotypes exhibit significant phenotypic and gene expression differences at early seedling stage (Singh et al, 2017(Singh et al, , 2018. The intra-Andean wild-landrace RIF excluded traits that may be found in modern cultivars and those controlling intergenepool variation.…”

“…Seeds were weighed and surface-sterilized with 50% commercial bleach for 5 min, rinsed in sterile deionized water, and imbibed overnight in the dark at 25°C. After removing the seed coat, seeds were germinated in paper rolls before the seedlings were transferred to root plates as described by Singh et al (2017). A single tank held 16 plates (1 seedling/plate), and a maximum of four tanks were placed in a Conviron E15 growth chamber.…”

Seed and seedling characteristics of hybrid chestnuts (Castanea spp.) derived from a backcross blight-resistance breeding program

“…Seed and early seedling morphology and physiology is thought to be influenced by the genetic makeup and environment of the parent plant more so than the genotype of the embryo (González-Rodrígueza et al 2011;Singh et al 2017). This is partly through maternal effects that affect provisioning of resources to embryos.…”

Maternal control of early life history traits affects overwinter survival and seedling phenotypes in sunflower (Helianthus annuusL.)

“…Despite that a lot of work has been dedicated to studying the ecological and evolutionary consequences of hybridization in plants, much less attention has been paid to how maternal parents influence the phenotypes of their offspring (i.e. maternal effects) immediately after hybridization (Kimball et al 2008;Piskurewicz et al 2016;Singh et al 2017). The maternal effect, defined by Roach and Wulff (1987) as "the contribution of the maternal parent to the phenotype of its offspring beyond the equal chromosomal contribution expected from each parent", can be arbitrarily split into two groups: i) maternal environment effects, where phenotypic differences in the offspring are due to differential environmental conditions experienced by the maternal parents (Chiang et al 2011;Fernández Farnocchia et al 2019); and ii) maternal genetic effects, where phenotypic differences in the offspring are due to the maternal parent´s phenotype or genotype (Roach & Wulff 1987;Pace et al 2015;Singh et al 2017).…”