Seedcoat splitting in peanut (Arachis hypogaea L.) can have direct effects on market quality, germination, and susceptibility of seeds to invasion by fungi. Six parental genotypes with differing degrees of seedcoat splitting were crossed with three non-splitting genotypes, and the F₁, F₂, and F₃ seedcoat generations were investigated to determine the inheritance of the seedcoat splitting trait and its effects on germination. Mature seeds were classified according to the number and extent of splits in the seedcoat. Individual seed weights and germination data were recorded.

In crosses involving genotypes with large differences in seed weight, the F₁ seedcoat generation tended to be closer to the smaller parent in splitting percentages. Highly significant phenotypic correlations were obtained between seed weight and seedcoat splitting which led to the conclusion that segregation for seed weight can confound or mask the seedcoat splitting trait.

In crosses of geneotypes with similar seed weight, the F₂ and F₃ seedcoat generations had mean seed weights below that of both parents. Natural selection for non-splitting seedcoats seemed to be involved in the decreased number of heavier seeds in those populations. Seeds with split seedcoat germinated less than non-split seeds under field and laboratory conditions. As a consequence of the lower germination percentage, the population means tended to skew toward the smaller seed weight, which was represented to a greater degree by the non-split seeds.

Genetic models were proposed for crosses in which the parents were similar in seed weight and significantly different in splitting percentage. F₂ populations revealed monogenic inheritance with additive effects in one cross, and also two unusual segregations which suggested duplicate additive and complementary gene action. Natural selection for non-split seeds appeared to bias the results. F₁ data, in some crosses, revealed some degree of dominance for the splitting trait, although subsequent generations presented seedcoat splitting as a recessive trait. It appears that the selective germination of split seeds affected the genetic ratios, and should be considered in further studies.