Molecular genetics of heterosis of the plant`s earliest stage, the embryo, using the large-seeded faba bean as model

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Heterosis of developing and mature single seeds will be analyzed. The seed is decisive at sowing and when becoming 'grain yield'. The seed has its own genetics: yet, xenia effects are mostly neglected: xenia, the direct impact of the seed's genotype on its own traits. Seeds show heterosis, but only very few experimental data are available. Is heterosis of seed size specific, caused by the parental seed size genes? Is it general, caused by many genes, hence similar to the green plant's yield heterosis? Two hypotheses will be tested: (1) Hybrid seeds become larger than inbred seeds: seed's genome-wide heterozygosity has a clear impact on its growth, the seed has its own heterosis; (2) Yield of a plant is greater if the growing seeds are heterozygous. Field experiments with orthogonal mating designs across several environments including a stress treatment are planned. Available prerequisites are: a crop very convenient for this research (faba bean), systems to individually detect selfed and crossed seeds competing within one fruit, near isogenic pollinators with contrasting genes for seed size, pollensterile lines and hybrids, inbred lines with known differences for marker similarity and for green plant's heterosis (from multi-environment field trials).